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Best Celestial Object of All Time

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    1
    Alpha Arietis

    Alpha Arietis

    • Category: Star
    Alpha Arietis (α Ari, α Arietis) is the Bayer designation for the brightest star in the northern zodiacal constellation of Aries. It has the traditional name Hamal, which comes from the Arabic phrase for "head of the ram", and the Flamsteed designation of 13 Arietis. With an apparent visual magnitude of 2.0, it among the brightest stars in the night sky. Based upon parallax measurements made with Hipparcos astrometry satellite, α Arietis is about 65.8 light-years (20.2 parsecs) from Earth. It is a giant star that may host an orbiting planet with a mass greater than Jupiter. The spectrum of this star matches a stellar classification of K2 III Ca-1, with the luminosity class of III indicating that it is an evolved giant star that has exhausted the supply of hydrogen at its core and is now on the red giant branch. The 'Ca-1' portion of the classification indicates that it shows weaker than normal lines of calcium in its spectrum. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is estimated to have about 50% more mass than the Sun, while interferometric measurements show it to be 15 times larger in diameter.
    6.50
    8 votes
    2
    IK Pegasi

    IK Pegasi

    • Category: Star
    IK Pegasi (or HR 8210) is a binary star system in the constellation Pegasus. It is just luminous enough to be seen with the unaided eye, at a distance of about 150 light years from the Solar System. The primary (IK Pegasi A) is a main sequence, A-class star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star and it has a periodic cycle of luminosity variation that repeats itself about 22.9 times per day. Its companion (IK Pegasi B) is a massive white dwarf—a star that has evolved past the main sequence and is no longer generating energy through nuclear fusion. They orbit each other every 21.7 days with an average separation of about 31 million kilometres, or 19 million miles, or 0.21 astronomical units (AU). This is smaller than the orbit of Mercury around the Sun. IK Pegasi B is the nearest known supernova progenitor candidate. When the primary begins to evolve into a red giant, it is expected to grow to a radius where the white dwarf can accrete matter from the expanded gaseous envelope. When the white dwarf approaches the Chandrasekhar limit of 1.38 solar masses, it may explode as a Type Ia supernova. This star system was catalogued in
    7.50
    6 votes
    3
    Eta Ursae Majoris

    Eta Ursae Majoris

    • Category: Star
    Eta Ursae Majoris (Eta UMa, η Ursae Majoris, η UMa) is a star in the constellation Ursa Major. It has the traditional names Alkaid (or Elkeid) and Benetnash (Benetnasch). Alkaid is the most eastern (leftmost) star in the Big Dipper (Plough) asterism. However, unlike most stars of the Big Dipper, it is not a member of the Ursa Major moving group. With an apparent visual magnitude of +1.84, it is the third brightest star in the constellation and one of the brightest stars in the night sky. This is a 10 million year old B-type main sequence star with a stellar classification of B3 V. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It has six times the mass of the Sun and 3.4 times the Sun's radius. Eta Ursae Majoris is radiating around 1,350 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of about 16,823 K, giving it the blue-white hue of a B-type star. This star is an X-ray emitter with a luminosity of 9.3 × 10 erg s.
    7.17
    6 votes
    4
    Beta Arietis

    Beta Arietis

    • Category: Star
    Beta Arietis (β Ari, β Arietis) is a binary star system in the constellation Aries, marking the Ram's second horn. It has the traditional name Sheratan (or Sharatan, Sheratim), and the Flamsteed designation 6 Arietis. The traditional name, in full Al Sharatan, is from the Arabic الشراطان aš-šarāţān "the two signs", a reference to the star having marked the northern vernal equinox together with Gamma Arietis several thousand years ago. In Chinese, 婁宿 (Lóu Su), meaning Bond (asterism), refers to an asterism consisting of β Arietis, γ Arietis and α Arietis. Consequently, β Arietis itself is known as 婁宿一 (Lóu Su yī, English: the First Star of Bond). Beta Arietis has an apparent visual magnitude of 2.66. Based on parallax measurements, it is located at a distance of 59.6 light-years (18.3 parsecs) from Earth. This is a spectroscopic binary star system consisting of a pair of stars orbiting around each other with a separation that can not currently be resolved with a conventional telescope. However, the pair have been resolved using the Mark III Stellar Interferometer at the Mount Wilson Observatory. This allows the orbital elements to be computed, as well as the individual masses of the
    8.20
    5 votes
    5
    Eta Canis Majoris

    Eta Canis Majoris

    • Category: Star
    Eta Canis Majoris (η CMa, η Canis Majoris) is a star in the constellation Canis Major. It has the traditional name Aludra. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin". This star, along with ε CMa (Adhara), δ CMa (Wezen) and ο CMa (Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins. In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow, refers to an asterism consisting of η Canis Majoris, δ Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris, κ Canis Majoris and π Puppis. Consequently, δ Canis Majoris itself is known as 弧矢二 (Hú Shǐ èr, English: the Second Star of Bow and Arrow.) Aludra shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter (absolute magnitude) than the Sun. A blue supergiant, Aludra has only been around a fraction of the time our Sun has, yet is already in the last stages of its life. It is still expanding and may become a red supergiant, or perhaps has already passed that phase, but in either case it will become a supernova within the next
    8.20
    5 votes
    6
    Theta Apodis

    Theta Apodis

    • Category: Star
    Theta Apodis (θ Aps, θ Apodis) is the Bayer designation for a star in the southern circumpolar constellation of Apus. It is a variable star with a mean apparent visual magnitude of 5.7, which, according to the Bortle Dark-Sky Scale, means it is a faint star but visible to the naked eye from dark suburban skies. The distance to Theta Apodis is approximately 370 light-years (110 parsecs), based upon parallax measurements made from the Hipparcos spacecraft. This is an evolved red giant that is currently on the asymptotic giant branch, with a stellar classification of M7 III. It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119 days. It is losing mass at the rate of 1.1 × 10 times the mass of the Sun per year through its stellar wind. Dusty material ejected from this star is interacting with the surrounding interstellar medium, forming a bow shock as the star moves through the galaxy. The stand-off distance for this front is located at about 0.134 ly (0.041 pc) from Theta Apodis. Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation
    8.20
    5 votes
    7
    Pi Andromedae

    Pi Andromedae

    • Category: Star
    Pi Andromedae (Pi And, π Andromedae, π And) is the Bayer designation for a binary star system in the northern constellation of Andromeda. With an apparent visual magnitude of 4.4, it is visible to the naked eye. It is located approximately 600 light-years (180 parsecs) from Earth. The pair is classified as a blue-white B-type main sequence dwarf with an apparent magnitude of +4.34. It is a spectroscopic binary with an orbital period of 143.6 days and an eccentricity of 0.56. There is a magnitude 8.6 companion 35.9 arcseconds away. At 55 arcseconds separation is an 11th magnitude companion. In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of π Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, π Andromedae itself is known as 奎宿六 (Kuí Sù liù, English: the Sixth Star of Legs.)
    7.00
    6 votes
    8
    Epsilon Orionis

    Epsilon Orionis

    • Category: Star
    Alnilam (Epsilon Orionis, ε Orionis) is a large blue supergiant star in the constellation of Orion. Its Flamsteed designation is 46 Orionis. It is the 30th brightest star in the sky (the 4th brightest in Orion) and is a blue-white supergiant. Together with Mintaka and Alnitak, the three stars make up the belt of Orion, known by many names across many ancient cultures. Alnilam is the middle star. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is also one of the 57 stars used in celestial navigation. It is at its highest point in the sky around midnight on December 15. Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium. Within the next million years, this star may turn into a red supergiant and explode as a supernova. It is surrounded by a molecular cloud, NGC 1990, which it brightens to make a reflection nebula. Its stellar winds may reach up to 2000 km/s, causing it to lose mass about 20 million times more rapidly than the Sun. The name Alnilam derives from the Arabic النظام an-niżām, related to the word نظم nażm "string of pearls". Related spellings are Alnihan
    6.00
    7 votes
    9
    Aldebaran

    Aldebaran

    • Category: Star
    Aldebaran (α Tau, α Tauri, Alpha Tauri) is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky. The name Aldebaran is Arabic (الدبران al-dabarān) and translates literally as "the follower", presumably because this bright star appears to follow the Pleiades, or "Seven Sisters" star cluster in the night sky. In 1997 a substellar companion was reported but subsequent observations have not confirmed this claim. Aldebaran is classified as a type K5III star. It is an orange giant star that has moved off the main sequence line of the Hertzsprung–Russell diagram. It has exhausted the hydrogen fuel in its core and hydrogen fusion has ceased there. Although not yet hot enough for fusing helium, the core temperature of the star has greatly increased due to gravitational pressure and the star has expanded to a diameter of 44.2 times the diameter of the Sun, approximately 61 million kilometres (see 10 gigametres for similar sizes). The Hipparcos satellite has measured it as 65.1 light years (20.0 pc) away, and it
    6.83
    6 votes
    10
    Delta Cephei

    Delta Cephei

    • Category: Star
    Delta Cephei (δ Cep, δ Cephei) is the Bayer designation for a binary star system located approximately 887 light-years away in the northern circumpolar constellation of Cepheus, the King. At this distance, the visual magnitude of the star is diminished by 0.23 as a result of extinction caused by gas and dust along the line of sight. It is the prototype of the Cepheid variable stars that undergo periodic changes in luminosity. Delta Cephei is among the closest stars of this type of variable to the Sun, with only Polaris being nearer. The variability of this star was discovered by John Goodricke in 1784, making it the second Cepheid variable to be discovered following Eta Aquilae earlier the same year. It was later found that there are two types of Cepheid variables, so Delta Cephei is now known as a type I (Classical) Cepheid. Delta Cephei's variability is caused by regular pulsation in the outer layers of the star. It varies from magnitude 3.48 to 4.37, and its stellar classification also varies, from about F5 to G3. The pulsation period is 5.366341 days, with a rise to maximum occurring quicker than the subsequent decline to minimum. Because the period of this class of variable is
    6.83
    6 votes
    11
    Zeta Ophiuchi

    Zeta Ophiuchi

    • Category: Star
    Zeta Ophiuchi (ζ Oph, ζ Ophiuchi) is a star located in the constellation of Ophiuchus. It has an apparent visual magnitude of 2.57, making it the third brightest star in the constellation. Parallax measurements give an estimated distance of roughly 366 light-years (112 parsecs) from the Earth. ζ Ophiuchi is an enormous star with more than 19 times the Sun's mass and eight times its radius. The stellar classification of this star is O9.5 V, with the luminosity class of V indicating that it is generating energy in its core by the nuclear fusion of hydrogen. This energy is being emitted from the outer envelope at an effective temperature of 34,000, giving the star the blue hue of an O-type star. It is rotating rapidly and may be close to the velocity at which it would begin to break up. The projected rotational velocity may be as high as 400 km s and it may be rotating at a rate of once per day. This is a young star with an age of only three million years. Its luminosity of the star is varying in a periodic manner similar to a Beta Cephei variable. This periodicity has a dozen or more frequencies ranging between 1–10 cycles per day. In 1979, examination of the spectrum of this star
    6.83
    6 votes
    12
    Pi Cassiopeiae

    Pi Cassiopeiae

    • Category: Star
    Pi Cassiopeiae (π Cas, π Cassiopeiae) is a star in the constellation Cassiopeia. π Cassiopeiae is a white A-type main sequence dwarf with a mean apparent magnitude of +4.95. It is approximately 174.3 light years from Earth. It is classified as a rotating ellipsoidal variable star and its brightness varies by 0.02 magnitudes with a period of 23.57 hours.
    8.75
    4 votes
    13
    Teegarden's star

    Teegarden's star

    • Category: Star
    Teegarden's Star, also known as SO J025300.5+165258, is an M-type brown dwarf in the constellation Aries, located about 12 light years from the Solar System. Despite its proximity to Earth it is a dim magnitude 15 and can only be seen through large telescopes. This star was found to have a very large proper motion of about 5 arc seconds per year. Only seven stars with such large proper motions are currently known. Teegarden's Star was discovered in 2003 using asteroid tracking data that had been collected years earlier. This data set is a digital archive created from optical images taken over a 5-year period by the Near Earth Asteroid Tracking (NEAT) program using two 1-m telescopes located on Maui. The star is named after the discovery team leader, Bonnard Teegarden, an astrophysicist at NASA's Goddard Space Flight Center. Astronomers have long thought it was quite likely that many undiscovered dwarf stars exist within 20 light years of Earth, as stellar population surveys show the count of known nearby dwarf stars to be lower than otherwise expected and these stars are dim and easily overlooked. Teegarden's team thought that these dim stars might be found by data mining some of
    7.40
    5 votes
    14
    Venus

    Venus

    • Category: Planet
    • Locations: Abeona Mons
    Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it has been referred to by ancient cultures as the Morning Star or Evening Star. Venus is classified as a terrestrial planet and is sometimes called Earth's "sister planet" owing to their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth). However, it has been shown to be very different from Earth in other respects. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It has the densest atmosphere of the four terrestrial planets, consisting mostly of carbon dioxide. The atmospheric pressure at the
    7.40
    5 votes
    15
    Algol

    Algol

    • Category: Star
    Algol (Beta Per, β Persei, β Per), known colloquially as the Demon Star, is a bright star in the constellation Perseus. It is one of the best known eclipsing binaries, the first such star to be discovered, and also one of the first (non-nova) variable stars to be discovered. Algol is actually a three-star system (Beta Persei A, B, and C) in which the large and bright primary Beta Persei A is regularly eclipsed by the dimmer Beta Persei B. Thus, Algol's magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every two days, 20 hours and 49 minutes during the roughly 10-hour long partial eclipses. There is also a secondary eclipse when the brighter star occults the fainter secondary. This secondary eclipse can only be detected photoelectrically. Algol gives its name to its class of eclipsing variable, known as Algol variables. In a 2012 paper, a claim is made that ancient Egyptians made detailed observations of the periodic variability of Algol, over 3200 years ago, in a papyrus document called the Cairo Calendar. Despite many claims in the modern literature that its ancient association with a demon-like creature (Gorgon in the Greek tradition, ghoul in the Arabic
    8.50
    4 votes
    16
    Polaris

    Polaris

    • Category: Star
    Polaris (α UMi, α Ursae Minoris, Alpha Ursae Minoris, commonly North Star, Northern Star or Pole Star, also Lodestar, sometimes Guiding star) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star. Based on measurements from the Hipparcos astrometry satellite, Polaris is estimated to be at a distance of about 434 light-years from Earth. It is a multiple star, consisting of the main star α UMi A, two smaller companions, α UMi B and α UMi Ab, and two distant components α UMi C and α UMi D. α UMi B was discovered in 1780 by William Herschel. α UMi A is a six solar mass F8 supergiant (Ib) or bright giant (II). The two smaller companions are: α UMi B, a 1.39 solar mass F3 main sequence star orbiting at a distance of 2400 AU, and α UMi Ab (or P), a very close dwarf with an 18.8 AU radius orbit and mass of roughly 1.5 solar masses . There are also two distant components α UMi C and α UMi D. Polaris B can be seen even with a modest telescope. It was found by William Herschel in 1780 using one of the most powerful telescopes at the time: a reflecting telescope that he had made. In 1929, it was discovered
    8.50
    4 votes
    17
    Epsilon Pegasi

    Epsilon Pegasi

    • Category: Star
    Epsilon Pegasi (ε Peg, ε Pegasi) is the brightest star in the northern constellation of Pegasus. It has the traditional name Enif. The name "Enif" is derived from the Arabic word for nose, due to its position as the muzzle of Pegasus. With an apparent visual magnitude of 2.4, this is a second-magnitude star that is readily visible to the naked eye. The distance to this star can be estimated using parallax measurements from the Hipparcos astrometry satellite, yielding a value of around 690 light-years (210 parsecs). In Chinese, 危宿 (Wēi Sù), meaning Rooftop (asterism), refers to an asterism consisting of ε Pegasi, α Aquarii and θ Peg. Consequently, ε Pegasi itself is known as 危宿三 (Wēi Sù sān, English: the Third Star of Rooftop.) This is an evolved star that has entered the supergiant stage, as indicated by the stellar classification of K2 Ib. It is estimated to be 12 times the Sun's mass. The measured angular diameter of this star, after correction for limb darkening, is 8.17 ± 0.09 mas. At the estimated distance of this star, this yields an enormous physical size of about 185 times the radius of the Sun. From this expanded envelope, it is radiating roughly 5,000 times the luminosity
    9.67
    3 votes
    18
    Delta Cassiopeiae

    Delta Cassiopeiae

    • Category: Star
    Delta Cassiopeiae (δ Cas, δ Cassiopeiae) is a star in the northern circumpolar constellation of Cassiopeia. It has the traditional names Ksora and Ruchbah, derived from the Arabic word ركبة rukbah meaning "knee". It is not to be confused with Alpha Sagittarii, which also is called Ruchbah or Rukbat. In Chinese, 閣道 (Gé Dào), meaning Flying Corridor, refers to an asterism consisting of δ Cassiopeiae, ι Cassiopeiae, ε Cassiopeiae, θ Cassiopeiae, ν Cassiopeiae and ο Cassiopeiae. Consequently, δ Cassiopeiae itself is known as 閣道三 (Gé Dào sān, English: the Third Star of Flying Corridor.) Delta Cassiopeiae is an eclipsing binary star system consisting of a pair of stars that orbit about each other over a period of 759 days. The combined apparent visual magnitude of the two stars is 2.68, making it readily observable with the naked eye. However, this magnitude varies between +2.68 mag and +2.74 as the stars pass in front of each other. Based on parallax measurements, this system is about 99.4 light-years (30.5 parsecs) from the Earth. The primary member of the system has a stellar classification of A5III-IVv, with the luminosity class of IV indicating that it has exhausted the hydrogen at
    7.20
    5 votes
    19
    14 Herculis

    14 Herculis

    • Category: Star
    14 Herculis or 14 Her is an orange dwarf star approximately 59 light-years away in the constellation Hercules. Because of its apparent magnitude, the star cannot be seen with the naked eye. As of 2006, it is thought that 14 Herculis has two extrasolar planets in orbit around the star. 14 Herculis is an orange dwarf star of the spectral type "K0V." It is thought that the star has 90 percent of the mass, 71 percent of the radius, and only 36 percent of the luminosity of the Sun. The star appears to be 2.7 times as enriched with elements heavier than hydrogen (based on its abundance of iron), in comparison to the Sun. In 1998 an extrasolar planet was discovered to orbit 14 Herculis, which received the designation 14 Herculis b. The planet is located in an eccentric, long-period orbit which takes around 4.8 years to complete. In 2005, a possible second planet was proposed, designated 14 Herculis c. The parameters of this planet are uncertain, but a recent analysis suggests it may lie in the 4:1 resonance with the inner planet, with an orbital period of almost 19 years at an orbital distance of 6.9 AU.
    8.25
    4 votes
    20
    Alpha Ursae Majoris

    Alpha Ursae Majoris

    • Category: Star
    Alpha Ursae Majoris (Alpha UMa, α Ursae Majoris, α UMa) is the second-brightest star in the constellation of Ursa Major (despite its Bayer designation of "alpha"). It has the traditional name Dubhe, and a rarer name Ak. This star forms part of the Big Dipper (also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards Polaris, the North Star. Dubhe is about 123 light years away and is a giant star that has evolved away from the main sequence after consuming the hydrogen at its core. It is a spectroscopic binary with a main sequence companion α UMa B that has a stellar classification of F0V. This star orbiting at a mean separation of about 23 astronomical units (AU) and completes an orbit every 44.4 years. More than 90,000 AU distant from this pair is a second binary system that includes an F-type star, making this a four star system. Although it is part of the constellation of Ursa Major, it does not form part of the Ursa Major Moving Group of stars that have a common motion through space.. Dubhe is the official star of the State of Utah. USS Dubhe (ID-2562) was a ship in the United States navy.
    7.00
    5 votes
    21
    Delta Andromedae

    Delta Andromedae

    • Category: Star
    Delta Andromedae (δ And, δ Andromedae) is a multiple star system in the northern constellation of Andromeda. Based upon parallax measurements, is located at a distance of approximately 105.5 light-years (32.3 parsecs) from the Earth. Apart from its Bayer designation, it was also given the title Delta by Elijah H. Burritt in his star atlas. In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of δ Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ι Piscium, ε Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, δ Andromedae itself is known as 奎宿五 (Kuí Su wǔ, English: the Fifth Star of Legs.) This is a long-period spectroscopic binary with an orbital period of approximately 15,000 days (41 years) and an overall apparent visual magnitude of approximately 3.28. The primary of the spectroscopic binary has a stellar classification of K3 III, indicating that it is a giant star. It most likely evolved from a F-type main sequence star after consuming the hydrogen at its core. The secondary is believed to be relatively faint, as it has not been
    7.00
    5 votes
    22
    Alpha Cassiopeiae

    Alpha Cassiopeiae

    • Category: Star
    Alpha Cassiopeiae (α Cas, α Cassiopeiae ) is a second magnitude star in the constellation Cassiopeia, with the traditional name Schedar, sometimes spelt Shedir. Though listed as the alpha star by Johann Bayer, Schedar's visual brightness closely rivals the beta star in the constellation, Caph. Depending on which passband is used, α Cas may be marginally brighter or dimmer than β Cas. However, recent calculations from the All-Sky catalog indicate that Schedar is the brightest in Cassiopeia, with a visual magnitude of 2.240. With Schedar located farther away from Earth than Caph, at 228 light years versus 54, Schedar is almost 18 times brighter that its rival insofar as intrinsic brightness is concerned. With a declination of 56° 32' North, Schedar is principally visible in the northern hemisphere. The star is yet discernible to most observers across the globe reaching as far south as Perth, Australia, Santiago, Chile and other settlements north ± 33° South latitude, albeit just above the horizon. Schedar is located in line-of-sight of the Milky Way galaxy, so there are other notable celestial objects one can view close to this star—the Pacman Nebula, NGC 436 and NGC 457 being a
    9.33
    3 votes
    23
    Iota Draconis

    Iota Draconis

    • Category: Star
    Iota Draconis (ι Dra, ι Draconis) is a star in the northern circumpolar constellation of Draco. It has the traditional name Edasich, a name that comes from the Arabic Al Ḍhiba' of Ulug Beg and the Dresden Globe, or Al dhīlī 'Male hyena' by Kazwini, with Eldsich being recorded in the Century Cyclopedia. A visually unremarkable star of apparent magnitude 3.3, in 2002 it was discovered to have a planet. From parallax measurements, this star is located at a distance of about 101.2 light-years (31.0 parsecs) from Earth. Edasich is larger and more massive than the Sun, with 1.8 times the mass and nearly 12 times the radius. The spectrum matches a stellar classification of K2 III, indicating this is an evolved star that has exhausted the supply of hydrogen at its core and left the main sequence of stars like the Sun. With an expanded outer envelope, this giant star is radiating over 55 times the luminosity of the Sun at an effective temperature of 4,545 K. This temperature gives it an orange hue that is a characteristic of K-type stars. It is rotating at a leisurely rate, with a period of around 434 days. In the past Iota Draconis has been suspected of variability. However, the star has
    8.00
    4 votes
    24
    Sigma Sagittarii

    Sigma Sagittarii

    • Category: Star
    Sigma Sagittarii (Sigma Sgr, σ Sagittarii, σ Sgr) is the second brightest star in the constellation Sagittarius. Its modern name Nunki is an Assyrian or Babylonian name recovered by archaeologists and made public by R. H. Allen. Nunki has an apparent magnitude of +2.05, making it readily visible to the naked eye. The distance to this star, determined using parallax measurements from the Hipparcos astrometry satellite, yields an estimated value of 228 light-years (70 parsecs) from Earth. Nunki has a spectrum matching a stellar classification of B2.5 V, which indicates this is a B-type main sequence star. The total luminosity of σ Sgr is 3300 times that of the Sun while it has a surface temperature of 18,890 K. X-ray emission has been detected from this star, which has an estimated X-ray luminosity of 1.2 × 10 erg s. Sigma Sgr has a magnitude +9.5 optical companion located 5.2 arcminutes away. Because it is close to the ecliptic, Nunki can be occulted by the Moon and very rarely by planets. The last occultation of Nunki by a planet took place on November 17, 1981, when it was occulted by Venus. Furthermore, Nunki is the brightest star that can be principally occulted by an exterior
    6.00
    6 votes
    25
    Alpha Herculis

    Alpha Herculis

    • Category: Star
    Alpha Herculis (α Her, α Herculis) is a multiple star system in the constellation Hercules. It has the traditional name Rasalgethi or Ras Algethi (Arabic: رأس الجاثي ra's al-jaθiyy‎ Head of the Kneeler), and the Flamsteed designation 64 Herculis. The traditional name "Head" comes from the fact that in antiquity Hercules was depicted upside down on the constellation maps. The term ra's al-jaθiyy or Ras al Djathi was appeared in the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, which was translated into Latin as Caput Ingeniculi. In Chinese astronomy, Rasalgethi is called 帝座, Pinyin: Dìzuò, meaning Emperor's Seat, because this star is marking itself and stand alone in Emperor's Seat asterism, Heavenly Market enclosure (see : Chinese constellation). 帝座 (Dìzuò) was westernized into Ti Tso by R.H. Allen, with the same meaning The angular diameter of the red giant, α Her, has been measured with an interferometer as 34 ± 0.8 mas, or 0.034 arcseconds. At an estimated distance of 110 parsecs from Hipparcos, this corresponds to a radius of about 280 million kilometers (or 170 million miles), which is roughly 400R☉ or 1.87 AU. If Rasalgheti were at the center of our Solar
    6.80
    5 votes
    26
    Eta Cassiopeiae

    Eta Cassiopeiae

    • Category: Star
    Eta Cassiopeiae (η Cas, η Cassiopeiae) is a star system in the northern circumpolar constellation of Cassiopeia. It has the traditional name Achird. Based upon parallax measurements, the distance to this system is 19.42 light-years (5.95 parsecs) from Earth. In Chinese, 王良 (Wáng Liáng), meaning Wang Liang, refers to an asterism consisting of η Cassiopeiae, β Cassiopeiae, κ Cassiopeiae, α Cassiopeiae and λ Cassiopeiae. Consequently, η Cassiopeiae itself is known as 王良三 (Wáng Liáng sān, English: the Third Star of Wang Liang.) The primary star in the Eta Cassiopeiae system has a stellar classification of G0 V, which makes it a G-type main-sequence star like the Sun. It therefore resembles what our Sun might look like if we were to observe it from Eta Cassiopeiae. The star has 97% of the mass of the Sun and 101% of the Sun's radius. It is of apparent magnitude 3.44, radiating 129% of the luminosity of the Sun from its outer envelope at an effective temperature of 6,087 K. It appears to be rotating at a leisurely rate, with a projected rotational velocity of 3.15 km s. The cooler and dimmer magnitude 7.51 companion is of stellar classification K7 V; a K-type main sequence star. It has
    6.80
    5 votes
    27
    Omega Cassiopeiae

    Omega Cassiopeiae

    • Category: Star
    Omega Cassiopeiae (ω Cas, ω Cassiopeiae) is a star in the constellation Cassiopeia. ω Cassiopeiae is a blue-white B-type giant with an apparent magnitude of +4.97. It is approximately 701 light years from Earth.
    6.80
    5 votes
    28
    Epsilon Indi

    Epsilon Indi

    • Category: Star
    Epsilon Indi (ε Ind, ε Indi) is a K-type main-sequence star approximately 12 light-years away from the Earth in the constellation of Indus. Two brown dwarfs, found in 2003, orbit the star. The constellation Indus (the Indian) first appeared in Johann Bayer's celestial atlas Uranometria in 1603. The 1801 star atlas Uranographia, by German astronomer Johann Elert Bode, places Epsilon Indi as one of the arrows being held in the left hand of the Indian. In 1847, Heinrich Louis d'Arrest compared the position of this star in several catalogues dating back to 1750, and discovered that it possessed a measureable proper motion. That is, he found that the star had changed position across the celestial sphere over time. In 1882–3, the parallax of Epsilon Indi was measured by astronomers David Gill and William L. Elkin at the Cape of Good Hope. They derived a parallax estimate of 0.22 ± 0.03 arcseconds. In 1923, Harlow Shapley of the Harvard Observatory derived a parallax of 0.45 arcseconds. During Project Ozma in 1960, this star was examined for artificial radio signals, but none were found. In 1972, the Copernicus satellite was used to examine this star for the emission of ultraviolet laser
    9.00
    3 votes
    29
    Eta Andromedae

    Eta Andromedae

    • Category: Star
    Eta Andromedae (Eta And, η Andromedae, η And) is a spectroscopic binary star in the constellation of Andromeda. It consists of two G-type subgiant or giant stars orbiting each other with a period of 115.7 days and has an overall apparent visual magnitude of approximately 4.403. Eta Andromedae was discovered to be a double-lined spectroscopic binary in a series of spectra taken in 1899 and 1900. Its orbit was computed in 1946 from spectroscopic observations. Because spectroscopy only reveals the radial velocity of a star towards or away from the viewer, such a computation does not determine all orbital elements. In observations made from 1990 to 1992, Eta Andromedae was resolved interferometrically by the Mark III Stellar Interferometer at Mount Wilson Observatory, California, United States. This allowed a more complete orbit to be computed and, in 1993, published. This star's location in the constellation Andromeda can be seen in the following diagram: In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium,
    7.75
    4 votes
    30
    Gamma Ursae Majoris

    Gamma Ursae Majoris

    • Category: Star
    Gamma Ursae Majoris (Gamma UMa, γ Ursae Majoris, γ UMa) is a star in the constellation Ursa Major It has the traditional name Phad, or Phecda. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Based upon parallax measurements with the Hipparcos astrometry satellite, it is located at distance of around 83.2 light-years (25.5 parsecs). It is more familiar to most observers in the northern hemisphere as the lower-left star forming the bowl of the Big Dipper, together with Dubhe (upper-right), Merak (lower-right) and Megrez (upper-left). Along with four other stars in this well-known asterism, Phecda forms an actual loose, association of stars known as the Ursa Major moving group. Like the other stars in the group, it is a main sequence star not unlike our Sun, although somewhat hotter, brighter and larger. Gamma Ursae Majoris is an Ae star, which is surrounded by an envelope of gas that is adding emission lines to the spectrum of the star; hence the 'e' suffix in the stellar classification of A0 Ve. It has 2.6 times the mass of the Sun, three times the Sun's radius, and an effective temperature of 9,355 K in its
    7.75
    4 votes
    31
    Mu Boötis

    Mu Boötis

    • Category: Star
    Mu Boötis (μ Boo, μ Boötis) is a triple star system in the constellation Boötes. It has the traditional name Alkalurops (also Inkalunis, Clava, and Venabulum), and the Flamsteed designation 51 Boötis. Mu Boötis is approximately 121 light-years from Earth. The name Alkalurops is from Greek καλαύροψ kalaurops "shepherd's staff", through the Arabic. It is known as 七公六 (the Sixth Star of the Seven Excellencies) in Chinese. The primary component, μ¹ Boötis, is a yellow-white F-type subgiant with an apparent magnitude of +4.31. Separated from the primary by 108 arcseconds in the sky is the binary star μ² Boötis, which has a combined spectral type of G1V and a combined brightness of +6.51 magnitudes. The components of μ² Boötis have apparent magnitudes of +7.2 and +7.8 and are separated by 2.2 arcseconds. They complete one orbit about their common centre of mass every 260 years.
    7.75
    4 votes
    32
    Ross 614

    Ross 614

    • Category: Star
    Ross 614 (V577 Monocerotis) is a red dwarf UV Cetiflare star and it is the primary member of a nearby binary star system in the constellation of Monoceros. This star has an magnitude of about 11, making it invisible to the unaided eye even though it is one of the stars nearest to the sun. This system is among the closest to our Sun at an estimated distance of about 13.3 light years. Because this star is so close to the Earth it is often the subject of study, hence the large number of designations by which it is known. This binary star system consists of two closely spaced low-mass red dwarf M-type stars. The secondary star is a dim magnitude 14 lost in the glare of the nearby primary star. The most recent determination of the system orbital elements comes from a study by George Gatewood using older sources along with data from the Hipparcos satellite. This study yielded an orbital period of about 16.6 years and a semi-major axis separation of about 1.1 arc seconds. The primary star was discovered in 1927 by F. E. Ross using the 40 in (100 cm) refractor telescope at the Yerkes Observatory. He noticed the high proper motion of this dim 11th magnitude star in his second-epoch plates
    7.75
    4 votes
    33
    Alphard

    Alphard

    • Category: Star
    Alphard (α Hya, α Hydrae, Alpha Hydrae) is the brightest star in the constellation Hydra. The name Alphard is from the Arabic الفرد (al-fard), "the solitary one", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In ancient China it formed part of an asterism called the "red bird". The European astronomer Tycho Brahe dubbed it Cor Hydræ, the heart of the snake. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Soheil al Fard, which was translated into Latin as Soheil Solitarius, meaning the bright solitary one. In Chinese, 星宿 (Xīng Sù), meaning Star (asterism), refers to an asterism consisting of Alphard, τ Hydrae, τ Hydrae, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428. Consequently, Alphard itself is known as 星宿一 (Xīng Sù yī, English: the First Star of Star.) Alphard has three times the mass of the Sun. The estimated age of this star is 420 million years and it has evolved away from the main sequence to become a giant star with a spectral classification of K3 and luminosity class between II and III. The angular diameter of this star has been measured using long
    6.60
    5 votes
    34
    Chi1 Orionis

    Chi1 Orionis

    • Category: Star
    Chi Orionis (χ Ori, χ Orionis) is a star about 28 light years away. It is in the constellation Orion. χ Ori is a G0V main-sequence star. It has a faint companion with a mass estimated at about 15% of the mass of the Sun, an orbital period of 14.1 years, and an estimated stellar class of M6. The companion orbits an average distance of 6.1 AU from the primary, but has a fairly high orbital eccentricity, ranging from 3.3 AU out to 8.9 AU from the primary. Because of this red dwarf companion, the likelihood of habitable planets in this system is low. χ Ori is a candidate stream star member of the Ursa Major Moving Group, although there is some evidence to the contrary.
    6.60
    5 votes
    35
    Epsilon Reticuli

    Epsilon Reticuli

    • Category: Star
    Epsilon Reticuli (Epsilon Ret, ε Reticuli, ε Ret) is a double star approximately 59 light-years away in the constellation of Reticulum. The primary component is an orange subgiant star, while the secondary is a white dwarf star. The two stars share a common motion through space and hence most likely form a binary star system. The brighter star should be easily visible without optical aid under dark skies in the southern hemisphere. In 2000, an extrasolar planet was confirmed to be orbiting the primary star in the system. The primary component is a subgiant star with a stellar classification of K2 IV. The fusing hydrogen in its core is coming to an end and it is in the process of expanding as a red giant. (The NStars project gave it a classification of K2 III, which would make it a giant star.) The secondary component is a white dwarf star located at a separation of at least 240 AU from the primary. It has a surface temperature between 9000 and 17000 K. On December 11, 2000, a team of astronomers announced the discovery of a planet Epsilon Reticuli b. With a minimum mass of 1.17 that of Jupiter and a similar radius, the planet moves around Epsilon Reticuli with an average separation
    6.60
    5 votes
    36
    Altair

    Altair

    • Category: Star
    Altair (Alpha Aquilae, Alpha Aql, α Aquilae, α Aql, Atair) is the brightest star in the constellation Aquila and the twelfth brightest star in the night sky. It is an A-type main sequence star with an apparent visual magnitude of 0.77 and is one of the vertices of the Summer Triangle (the other two vertices are marked by Deneb and Vega). Altair rotates rapidly, with a velocity at the equator of approximately 286 km/s. A study with the Palomar Testbed Interferometer revealed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation. Other interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon. Altair is located 16.7 light-years (5.13 parsecs) from Earth and is one of the closest stars visible to the naked eye. Along with Beta Aquilae and Gamma Aquilae, it forms the well-known line of stars sometimes referred to as the Family of Aquila or Shaft of Aquila. Altair is a type-A main sequence star with approximately 1.8 times the mass of the Sun and 11 times its luminosity. Altair possesses an extremely rapid rate of rotation; it has a rotational period of approximately 9 hours. For
    5.67
    6 votes
    37
    Barnard's star

    Barnard's star

    • Category: Star
    Barnard's Star ( /ˈbɑrnərd/), also known occasionally as Barnard's "Runaway" Star, is a very low-mass red dwarf star about six light-years away from Earth in the constellation of Ophiuchus, the Snake-holder. Barnard's Star is the fourth-closest known individual star to the Sun, after the three components of the Alpha Centauri system. Despite its proximity, Barnard's Star, at a dim apparent magnitude of about nine, is not visible with the unaided eye; however, it is much brighter in the infrared than it is in visible light. The star is named for American astronomer E.E. Barnard. He was not the first to observe the star, but in 1916 he measured its proper motion as 10.3 arcseconds per year, which remains the largest-known proper motion of any star relative to the Sun. Barnard's Star has been the subject of much study, and it has probably received more attention from astronomers than any other class M dwarf star due to its proximity and favorable location for observation near the celestial equator. Historically, research on Barnard's Star has focused on measuring its stellar characteristics, its astrometry, and also refining the limits of possible extrasolar planets. Although
    5.67
    6 votes
    38
    Beta Canis Majoris

    Beta Canis Majoris

    • Category: Star
    Beta Canis Majoris (β CMa, β Canis Majoris) is a star in the southern constellation of Canis Major, the 'greater dog', and is located at a distance of about 500 light-years (150 parsecs) from the Earth. In the modern constellation it lies at the position of the dog's head. It has the traditional name Murzim, Al-Murzim or Mirzam, which is derived from the Arabic (مرزم) for 'The Herald', and probably refers to its position, heralding Sirius in the night sky (i.e., rising before it). In Chinese, 軍市 (Jūn Shì), meaning Market for Soldiers, refers to an asterism consisting of β Canis Majoris, ν Canis Majoris, 15 Canis Majoris, π Canis Majoris, ο Canis Majoris and ξ Canis Majoris. Consequently, β Canis Majoris itself is known as 軍市一 (Jūn Shì yī, English: the First Star of Market for Soldiers). From this Chinese name arose the name Kuen She. The Dunhuang Star Chart noted β Canis Majoris as Yeji "Pheasant Cock", though was located about 10 degrees too far north of its correct position. Murzim is a Beta Cephei variable that varies in apparent magnitude between +1.95 and +2.00 over a six-hour period, a change in brightness that is too small to be discerned with the naked eye. It exhibits this
    7.50
    4 votes
    39
    Saturn

    Saturn

    • Category: Planet
    • Locations: Great White Spot
    Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god Saturn, its astronomical symbol (♄) represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times as massive as Earth. Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer. The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is slightly weaker than Earth's and around one-twentieth the strength of Jupiter's. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph), faster than on Jupiter, but not as fast as those on Neptune. Saturn has a prominent ring system that
    7.50
    4 votes
    40
    Zeta Puppis

    Zeta Puppis

    • Category: Star
    Zeta Puppis (Zeta Pup, ζ Puppis, ζ Pup) is a star in the constellation of Puppis. It is also known by the traditional names Naos ( /ˈneɪ.ɒs/, from the Greek ναύς "ship") and Suhail Hadar (سهيل هدار, possibly "roaring bright one") in Arabic. Its spectral class is O4If, making it an exceptionally hot star, and it is one of the sky's few naked-eye class O-type stars. Its surface temperature is 42,400 K, or about seven times hotter than the surface of the Sun. Its mass is 40 solar masses. Unlike many other stars at such great distance, the precise parameters for Zeta Puppis including its velocity are known, and can extrapolate back to the region where it was formed, a molecular cloud in Vela. We can therefore derive a much more accurate distance than we can with, for example, Deneb. 2008 reductions of Hipparcos raw data give a distance of 335 parsecs (1,093 ly) ± 4%, and for Deneb, 475 pc ± 20%. Zeta Puppis is an extreme blue supergiant, one of the brightest stars in the Milky Way in terms of absolute magnitude. Visually, it is 21,000 times more powerful than the Sun, but being an extreme blue star most of its radiation is in the ultraviolet, and when this is considered it is
    7.50
    4 votes
    41
    Beta Ursae Minoris

    Beta Ursae Minoris

    • Category: Star
    Beta Ursae Minoris (β UMi, β Ursae Minoris) is the brightest star in the bowl of the "Little Dipper" (which is part of the constellation Ursa Minor), and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. It has the traditional name Kochab. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star can be deduced from the parallax measurements made during the Hipparcos, yielding a value of 130.9 light-years (40.1 parsecs). Kochab and its neighbor Pherkad are both naked eye stars and are sometimes referred to as the "Guardians of the Pole". They served as twin pole stars, Earth's North pole stars, from 1500 BC until 500 AD. Neither star was as proximitous to the pole as Polaris is now. Due to precession of the equinoxes, the previous holder of the title was Thuban, and the next was the present-day Polaris. This succession of pole stars is a result of earth's precessional motion. This is a giant star with a stellar classification of K4 III. It is 130 times more luminous than the Sun. Kochab has reached a state in its evolution where the outer envelope has expanded to 42 times the girth of the
    8.67
    3 votes
    42
    Eta Aquilae

    Eta Aquilae

    • Category: Star
    Eta Aquilae (η Aql, η Aquilae) is the Bayer designation for a star in the equatorial constellation of Aquila, the eagle. It was once part of the former constellation Antinous. On average, this star has an apparent visual magnitude of 3.87, making it one of the brighter members of Aquila. Based upon parallax measurements made during the Hipparcos mission, this star is located at a distance of roughly 1,382 light-years (424 parsecs), although the parallax estimate has a 44% margin of error. This is a Cepheid variable star, with an apparent magnitude that ranges from 3.5 to 4.4 over a period of 7.176641 days. Along with Delta Cephei, Zeta Geminorum and Beta Doradus, it is one of the most prominent naked eye Cepheids; that is, both the star itself and the variation in its brightness can be distinguished with the naked eye. Some other Cepheids such as Polaris are bright but have only a very small variation in brightness. At the relatively young age of 26 million years, this massive star has burned through the hydrogen fuel at its core and evolved into a supergiant, giving it a baseline stellar classification of F6 Ibv. The Ib luminosity class indicates this is a less luminous type of
    8.67
    3 votes
    43
    Delta Scorpii

    Delta Scorpii

    • Category: Star
    Delta Scorpii (δ Sco, δ Scorpii) is a star in the constellation Scorpius. It has the traditional name Dschubba (or Dzuba, from Arabic jabhat, "forehead" (of the scorpion) or also Iclarcrau or Iclarkrav. Because Delta Scorpii is near the ecliptic it is occasionally occulted by the Moon, or (extremely rarely) by planets. Delta Scorpii is a proper motion member of the Upper Scorpius subgroup of the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.. The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs). A recent analysis of the HR diagram position for Delta Scorpii estimates its effective temperature to be 27,400 Kelvin with a luminosity of 38,000 Suns, consistent with an isochronal age of 9-10 million years and an estimated mass of 14.6-14.9 solar masses. In June 2000, Delta Scorpii was observed by Sebastian Otero to be 0.1 magnitudes brighter than normal. Its brightness has varied since then and has reached as high as magnitude 1.65, altering the familiar appearance of Scorpius. Spectra taken after the outburst began have shown that the star
    10.00
    2 votes
    44
    Gamma Leonis

    Gamma Leonis

    • Category: Star
    Gamma Leonis (γ Leo, γ Leonis) is a binary star system in the constellation Leo. It has the traditional name Algieba or Al Gieba. The name Algieba originates from the Arabic الجبهة Al-Jabhah, meaning the forehead. Despite this meaning, the star actually appears in the mane of Leo. The star's Latin name is Juba. It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese. Xuanyuan is the name of Yellow Emperor. Algieba, as a binary system, consists of two stars. The brighter component has an apparent magnitude of +2.28 and is of spectral class K1-IIIbCN-0.5. The giant K star has a surface temperature of 4,470 K, a luminosity 180 times that of Earth's Sun, and a diameter 23 times that of the Sun. The companion star has an apparent magnitude of +3.51 and belongs to the spectral class G7IIICN-I. The giant G star has a temperature of 4,980 K, a luminosity of 50 times that of the Sun, and a diameter 10 times that of the Sun. With angular separation of just over 4", the two stars are at least 170 AU apart (four times the distance between Pluto and the Sun), and have an orbital period of over 500 years. Because the orbital period is so long, only a fraction of the full path has been
    10.00
    2 votes
    45
    Sirius

    Sirius

    • Category: Star
    Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Σείριος Seirios ("glowing" or "scorcher"). The star has the Bayer designation Alpha Canis Majoris (α CMa). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main-sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, called Sirius B. The distance separating Sirius A from its companion varies between 8.1 and 31.5 AU. Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite, the Sirius system is one of Earth's near neighbors; for Northern-hemisphere observers between 30 degrees and 73 degrees of latitude (including almost all of Europe and North America), it is the closest star (after the Sun) that can be seen with a naked eye. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years.
    7.25
    4 votes
    46
    V838 Monocerotis

    V838 Monocerotis

    • Category: Star
    V838 Monocerotis (V838 Mon) is a red variable star in the constellation Monoceros about 20,000 light years (6 kpc) from the Sun, and possibly one of the largest known stars. The previously unknown star was observed in early 2002 experiencing a major outburst. Originally believed to be a typical nova eruption, it was then realized to be something completely different. The reason for the outburst is still uncertain, but several conjectures have been put forward, including an eruption related to stellar death processes and a merger of a binary star or planets. The remnant is evolving rapidly. As of 2009 it has increased in both temperature (now class M6.3I and 3,270K) and luminosity (now 15,000 times solar), but decreased in radius (now 380 times the sun) although the ejecta continues to expand. The opaque ejected dust cloud has completely engulfed the B-type companion. On January 6, 2002, an unknown star was seen to brighten up in Monoceros, the Unicorn. Being a new variable star, it was designated V838 Monocerotis, the 838th variable star of Monoceros. The initial light curve resembled that of a nova, an eruption that occurs when enough hydrogen gas has accumulated on the surface of
    7.25
    4 votes
    47
    Alpha Andromedae

    Alpha Andromedae

    • Category: Star
    Alpha Andromedae (Alpha And, α And, α Andromedae), which has the traditional names Alpheratz (or Alpherat) and Sirrah (or Sirah), is the brightest star in the constellation of Andromeda. Located immediately northeast of the constellation of Pegasus, it is the northeastern star of the Great Square of Pegasus. As a connecting star to Pegasus, it is also known as δ Pegasi, though this name is no longer used (another such doubly named connecting star is β Tauri). It is located 97 light-years from Earth. Although it appears to the naked eye as a single star, with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high levels of mercury, manganese, and other elements, including gallium and xenon. It is the brightest mercury-manganese star known. This star has for long been treated as being in Pegasus and simultaneously in Andromeda, and Johann Bayer catalogued it as both α Andromedae and δ Pegasi. The radial velocity of a star away from or towards the observer can be determined by measuring
    8.33
    3 votes
    48
    Cor Caroli

    Cor Caroli

    • Category: Star
    Cor Caroli (α CVn, α Canum Venaticorum, Alpha Canum Venaticorum, originally known by the more elaborate Cor Caroli Regis Martyris) is the brightest star in the northern constellation Canes Venatici. The name Cor Caroli means Charles' heart, and was named by Sir Charles Scarborough in honour of Charles I, who was executed in the aftermath of the English Civil War, and otherwise associated to Charles II of England, his son, who was restored to the throne after the interregnum following his father's death. In Chinese, 常陳 (Cháng Chén), meaning Imperial Guards, refers to an asterism consisting of α Canum Venaticorum, 10 Canum Venaticorum, β Canum Venaticorum, 6 Canum Venaticorum, 2 Canum Venaticorum, 67 Ursae Majoris. Consequently, α Canum Venaticorum itself is known as 常陳一 (Cháng Chén yī, English: the First Star of Imperial Guards.) From this Chinese name, the name Chang Chen was appeared. Cor Caroli is a binary star with a combined apparent magnitude of 2.81. The two stars are 19.6 arcseconds apart in the sky and are easily resolved in small telescopes. The system lies approximately 110 light years from Earth. The brighter of the two stars is designated α² Canum Venaticorum, the
    8.33
    3 votes
    49
    Deneb

    Deneb

    • Category: Star
    Deneb (α Cyg, α Cygni, Alpha Cygni) is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars. However, its exact distance (and hence luminosity) has been difficult to calculate, so it is anywhere between 54,000 and 196,000 times as luminous as the sun. Other names include Arided and Aridif, but these have fallen out of use. Deneb lies at a vertex of a widely spaced asterism called the Summer Triangle, the other two members of which are the zero-magnitude stars Vega in the constellation Lyra and Altair in Aquila. This formation is the approximate shape of a right triangle, with Deneb located at one of the acute angles. The Summer Triangle is recognizable in the northern skies for there are few other bright stars in its vicinity. Deneb's absolute magnitude is currently estimated as −8.4, placing it among the most luminous stars known, with an estimated luminosity nearly 200,000 times that of our Sun. This is towards the upper end of various published values over the last few
    8.33
    3 votes
    50
    Luyten 726-8

    Luyten 726-8

    Luyten 726-8 (also known as Gliese 65) is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. Luyten 726-8B is also known under the variable star designation UV Ceti, being the archetype for the class of flare stars. The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8. The two stars are of nearly equal brightness, with visual magnitudes of 12.57 and 11.99 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320 Gm). The Luyten 726-8 system is approximately 2.63 parsecs (8.58 ly) from Earth's Solar System, in the constellation Cetus, and is thus the sixth-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.88 pc (2.87 ly) away from it. If km/s then approximately 28,700 years ago Luyten 726-8 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun. Luyten-726-8A was found to be a variable star and given the
    8.33
    3 votes
    51
    Mu Arae

    Mu Arae

    • Category: Star
    Mu Arae (μ Ara, μ Arae), often referred to by its designation in the Henry Draper catalogue HD 160691, is a main sequence G-type star around 50 light-years away from Earth in the constellation of Ara. The star has a planetary system with four known planets, three of them with masses comparable to that of Jupiter. The system's innermost planet was the first "hot Neptune or super-Earth" to be discovered. According to measurements made by the Hipparcos astrometric satellite, Mu Arae exhibits a parallax of 64.47 milliarcseconds as the Earth moves around the Sun. When combined with the known distance from the Earth to the Sun, this means the star is located at a distance of 50.6 light years (15.51 parsecs). Seen from Earth it has an apparent magnitude of +5.12 and is visible to the naked eye. Asteroseismic analysis of the star reveals it is approximately 10% more massive than the Sun and significantly older, at around 6,340 million years. The radius of the star is 36% greater than that of the Sun and it is 90% more luminous. The star contains twice the abundance of iron relative to hydrogen of our Sun and is therefore described as metal-rich. Mu Arae is also more enriched than the Sun
    8.33
    3 votes
    52
    Theta Cassiopeiae

    Theta Cassiopeiae

    • Category: Star
    Theta Cassiopeiae (θ Cas, θ Cassiopeiae) is a star in the constellation Cassiopeia. It has the traditional name Marfark or Marfak, which it shares with μ Cassiopeiae, and the name was from Al Marfik or Al Mirfaq (المرفق), meaning "the elbow". In Chinese, 閣道 (Gé Dào), meaning Flying Corridor, refers to an asterism consisting of θ Cassiopeiae, ι Cassiopeiae, ε Cassiopeiae, δ Cassiopeiae, ν Cassiopeiae and ο Cassiopeiae. Consequently, θ Cassiopeiae itself is known as 閣道四 (Gé Dào sì, English: the Fourth Star of Flying Corridor.) θ Cassiopeiae is a white A-type main sequence dwarf with an apparent magnitude of +4.34. It is approximately 137 light years from Earth.
    8.33
    3 votes
    53
    AU Microscopii

    AU Microscopii

    • Category: Star
    AU Microscopii (AU Mic) is a small star located 32.3 light-years (9.9 parsecs) away – about 8 times as far as our closest star after the Sun. The apparent visual magnitude of AU Microscopii is 8.73, which is too dim to be seen with the naked eye. It was given this designation because it is in the southern constellation Microscopium and is a variable star. Like β Pictoris, AU Microscopii has a circumstellar disk of dust known as a debris disk. AU Mic is a young star at only 12 million years old; less than 1% of the age of the Sun. With a stellar classification of M1 Ve, it is red dwarf star with a physical radius of 60% that of the Sun. Despite being more than half the Sun's mass, it is radiating only 9% as much luminosity as the Sun. This energy is being emitted from the star's outer atmosphere at an effective temperature of 3,730 K, giving it the cool orange-red hued glow of an M-type star. AU Microscopii is a member of the β Pictoris moving group. AU Microscopii may be gravitationally bound to the binary star system AT Microscopii. AU Microscopii has been observed in every part of the electromagnetic spectrum from radio to X-ray and is known to undergo flaring activity at all
    9.50
    2 votes
    54
    Gliese 710

    Gliese 710

    • Category: Star
    Gliese 710 is a star in the constellation Serpens Cauda with an apparent visual magnitude of 9.69. It has a stellar classification of K7 Vk, which means it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. (The suffix 'k' indicates that the spectrum shows absorption lines from interstellar matter.) The mass of this star is about 60% of the Sun's mass and it has an estimated 67% of the Sun's radius. It is a suspected variable star that may vary in magnitude from 9.65–9.69. This star is currently about 63.8 light-years (19.6 parsecs) from Earth, but its proper motion, distance, and radial velocity indicate that it will approach within a very small distance—perhaps under one light year—from the Sun within 1.4 million years, based on past and current Hipparcos data. At closest approach it will be a first-magnitude star about as bright as Antares. The proper motion of Gliese 710 is very small for its distance, meaning it is traveling nearly directly in our line of sight; compare for example with Arcturus. In a time interval of ±10 million years from the present, Gliese 710 is the star whose combination of mass and close approach
    9.50
    2 votes
    55
    HD 101930

    HD 101930

    • Category: Star
    HD 101930 is a dim 8th magnitude star located approximately 99 light years away in the constellation of Centaurus. It is an orange dwarf (spectral class K2V), somewhat dimmer and cooler than our Sun. In 2005, the discovery of a planet orbiting the star was announced. This is another discovery using the radial velocity method with the HARPS spectrograph.
    9.50
    2 votes
    56
    Thuban

    Thuban

    • Category: Star
    Thuban also known by its Bayer designation Alpha Draconis (α Draconis, α Dra) is a star (or star system) in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star in ancient times. Thuban is an Arabic word for snake ثعبان thuʿbān. Even though Johann Bayer gave Thuban the designation Alpha, its apparent magnitude of 3.65 is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), whose apparent magnitude is 2.24. Given good viewing conditions, Thuban is relatively easy to spot in the night sky, due to its location in relation to the Big Dipper asterism of Ursa Major. While it is well known that the two outer stars of the 'dipper' point to the modern-day pole star Polaris, it is less well known that the two inner stars, Phecda and Megrez, point to Thuban, just 15 degrees of arc from Megrez. Thuban is not bright enough to be viewed from badly light-polluted areas. Due to the precession of Earth's rotational axis, Thuban was the naked-eye star closest to the north pole from 3942 BC, when it moved farther north than Theta Boötis, until 1793
    9.50
    2 votes
    57
    Sun

    Sun

    • Category: Star
    The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684 km, about 109 times that of Earth, and its mass (about 2×10 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,628 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others. The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. The Sun's stellar classification, based on spectral class, is G2V, and is informally designated as a yellow dwarf, because its visible radiation is most intense in
    7.00
    4 votes
    58
    Beta Comae Berenices

    Beta Comae Berenices

    • Category: Star
    Beta Comae Berenices (β Comae Berenices, β Com) is a main sequence dwarf star in the northern constellation of Coma Berenices. It is located at a distance of about 29.78 light-years (9.13 parsecs) from Earth. The Greek letter beta (β) usually indicates that the star has the second highest visual magnitude in the constellation. However, with an apparent visual magnitude of 4.3, this star is slightly brighter than α Comae Berenices. It can be seen with the naked eye, but may be too dim to be viewed from a built-up urban area. This star is similar to our own Sun, being only slightly larger and brighter in absolute magnitude. It has a stellar classification of G0 V, compared to G2 V for the Sun. The effective temperature of the outer envelope is 5,936 K, giving it a yellow hue of a G-type star. In terms of age it is younger than the Sun, being about 3 billion years old. Observations of short term variations in the chromatic activity suggest that the star undergoes differential rotation, with a rotation period of about 11–13 days. Its surface has a measured activity cycle of 16.6 years, compared to 11 years on our Sun. It may also have a secondary activity cycle of 9.6 years. At one
    6.00
    5 votes
    59
    Merope

    Merope

    • Category: Star
    Merope (23 Tauri) is a star in the constellation Taurus and a member of the Pleiades star cluster. It is approximately 360 light years from Earth. Merope is a blue-white B-type subgiant with a mean apparent magnitude of +4.14. Richard Hinckley Allen described the star as lucid white and violet. It has a luminosity of 630 times that of the Sun and a surface temperature of 14,000 kelvins. Merope's mass is roughly 4.5 solar masses and has a radius more than 4 times as great as the Sun's. It is classified as a Beta Cephei type variable star and its brightness varies by 0.01 magnitudes. Surrounding Merope is the Merope Nebula. Part of the nebula that the Pleiades Cluster is currently passing through, it appears brightest around Merope and is listed in the Index Catalogue as number IC 349.
    6.00
    5 votes
    60
    Albireo

    Albireo

    • Category: Star
    Albireo (β Cyg, β Cygni, Beta Cyg, Beta Cygni) is the fifth brightest star in the constellation Cygnus. Although it has the Bayer designation beta, it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni. Albireo appears to the naked eye to be a single star of magnitude 3 but through a telescope, even low magnification views resolve it into a double star. The brighter yellow star (actually itself a very close binary system) makes a striking colour contrast with its fainter blue companion star. Albireo is 380 light-years (120 pc) away from the Earth. When viewed with the naked eye, it appears to be a single star. However, in a telescope it readily resolves into a double star, consisting of Albireo A (amber, apparent magnitude 3.1), and Albireo B (blue-green, apparent magnitude 5.1). Separated by 35 seconds of arc, the two components provide one of the best contrasting double stars in the sky due to their different colors. It is not known whether the two components are orbiting around each other in a physical binary system. If they are, their orbital period is probably at least 100,000 years. In 1976, component A was itself discovered to be a binary star, using speckle
    8.00
    3 votes
    61
    Beta Draconis

    Beta Draconis

    • Category: Star
    Beta Draconis (β Draconis, β Dra) is the third brightest star in the northern circumpolar constellation of Draco. It has the traditional name Rastaban, which has also been used for Gamma Draconis. With an apparent visual magnitude of 2.79, it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite, it lies at a distance of about 380 light-years (120 parsecs) from Earth. Compared to the Sun, this is an enormous star with six times the mass and roughly 40 times the radius. At this size, Beta Draconis is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K, giving it the yellow hue of a G-type star. The spectrum matches a stellar classification of G2 Ib–IIa, with the luminosity class notation Ib–IIa indicating it lies part way between the bright giant and supergiant stages of its stellar evolution. It is about 67 million years old. This is a binary star system, with a binary star designation of ADS 10611, in which the supergiant is orbited by a dwarf companion once every four millennia or so. The traditional name, from the Arabic phrase ra's ath-thu'ban
    8.00
    3 votes
    62
    Beta Gruis

    Beta Gruis

    • Category: Star
    Beta Gruis (β Gruis, β Gru) is the second brightest star in the southern constellation of Grus. It was once considered the rear star in the tail of the constellation of the (Southern) Fish: it, with α, δ, θ. ι, and λ Gru, belonged to Piscis Austrinus in traditional Arabic astronomy. This is a red giant star with an estimated mass of about 2.4 times that of the Sun and a surface temperature of approximately 3,480 K, just over half the surface temperature of the Sun. This low temperature accounts for the dull red color of an M-type star. The total luminosity is about 2,500 times that of the Sun, and it has estimated 180 times the Sun's radius. Beta Gruis is a type semiregular variable (SRb) star that varies in magnitude by about 0.4. It varies between intervals when it displays regular changes with a 37 day periodicity and times when it undergoes slow irregular variability. Beta Gruis played a crucial part in Perth Observatory's tracking of comet 2000 WM1 LINEAR in December 2001.
    8.00
    3 votes
    63
    BG Geminorum

    BG Geminorum

    • Category: Star
    BG Geminorum is long period eclipsing binary star system which contains a K0 I secondary star in orbit around a primary star. The primary star has a mass at least 3.5 times that of the sun and could either be a B star (see Stellar Classification) or a black hole. Material from the K0 star is transferred to an accretion disk surrounding the unidentified primary star. BG Gem was first observed by Hoffmeister (1933) and Jensch (1938) - initially an RV Tau star candidate with an uncertain period of ~ 60 days and a photographic magnitude of ~ 14. Until 1992, BG Gem remained in the General Catalog of Variable Stars (GCVS), when Benson et al. (2000) discovered an ellipsoidal variation with an optical magnitude of about 0.5, and improved the accuracy of the period to 91.645 days. Using light curves, a deep primary eclipse was revealed at shorter wavelengths (less than 4400Å), and a shallow eclipse at longer wavelengths.
    8.00
    3 votes
    64
    Iota Cassiopeiae

    Iota Cassiopeiae

    • Category: Star
    Iota Cassiopeiae (ι Cas, ι Cassiopeiae) is a star system in the constellation Cassiopeia. It is approximately 141.6 light years from Earth. The primary component, ι Cassiopeiae A, is a white A-type main sequence dwarf with a mean apparent magnitude of +4.64. It is classified as an α² Canum Venaticorum type variable star and the brightness of the system varies from magnitude +4.45 to +4.53 with a period of 1.74 days. Component A is a spectroscopic binary. Its unresolved companion has an orbital period of 52.4 years and is separated from the primary by 0.113 arcseconds, or at least 5 AU. The second astrometric component, ι Cassiopeiae B, is a yellow-white F-type main sequence dwarf with an apparent magnitude of +6.89. It is 2.27 arcseconds, or at least 100 AU, from the primary. It has an orbital period of 840 years. The third astrometric component, ι Cassiopeiae C, is a yellow G-type dwarf, with an apparent magnitude of +8.40. It is 7.3 arcseconds (at least 300 AU) from the primary.
    6.75
    4 votes
    65
    15462 Stumegan

    15462 Stumegan

    • Category: Asteroid
    15462 Stumegan (1999 AV1) is a Main-belt asteroid discovered on January 8, 1999. The asteroid was discovered at Kitt Peak National Observatory as part of the Spacewatch project. It is named for Stu Megan, who discovered the first Spacewatch FMO Project asteroid to attain an official IAU MPEC designation.
    9.00
    2 votes
    66
    Tau Boötis

    Tau Boötis

    • Category: Star
    Tau Boötis (τ Boo, τ Boötis) is a yellow-white dwarf approximately 51 light-years away in the constellation of Boötes. The system is also a binary star system, with the secondary star being a red dwarf. As of 1999, an extrasolar planet has been confirmed to be orbiting the primary star. The system is a binary. The primary component is a yellow-white dwarf (spectral type F7 V) and secondary is a dim red dwarf (spectral type M2 V). The system is relatively nearby, distance being about 51 light years. The primary star should be easily visible to the unaided eye under dark skies. The primary star, Tau Boötis A is a yellow-white dwarf. It is 20% more massive than our Sun and thus is somewhat brighter and hotter. It has a radius 1.9 times solar, and is probably about 1300 million years old. Since it is more massive than the Sun, its lifespan is shorter being less than 6000 million years. Tau Bootis is the first star apart from the sun to be observed changing the polarity of its magnetic field. It is also listed as a suspected variable star. However, the star is not variable. Tau Boötis B (with a capital B, as opposed to the planet) is a dim red dwarf orbiting the primary star at a
    9.00
    2 votes
    67
    Alpha Persei

    Alpha Persei

    • Category: Star
    Alpha Persei (Alpha Per, α Persei, α Per) is the brightest star in the northern constellation of Perseus, just outshining the constellation's best known star, Algol. Known by the traditional names Mirfak and Algenib, it is a circumpolar star when viewed from the latitude of New York City or higher. It has an apparent visual magnitude of 1.8, placing it among the brightest stars in the sky. Mirfak lies in the midst of a cluster of stars eponymously named the Alpha Persei Cluster, or Melotte 20, which is easily visible in binoculars and includes many of the fainter stars in the constellation. The distance to this star has been determined using the parallax technique, putting it 510 light-years (160 parsecs) away. The spectrum of Alpha Persei matches a stellar classification of F5 Ib, revealing it to be a supergiant star in the latter stages of its evolution. It has a similar spectrum to Procyon, though the latter star is much less luminous. This difference is highlighted in their spectral designation under the Yerkes spectral classification, published in 1943, where stars are ranked on luminosity as well as spectral typing. Procyon is thus F5 IV, a subgiant star. Since 1943, the
    7.67
    3 votes
    68
    Epsilon Apodis

    Epsilon Apodis

    • Category: Star
    Epsilon Apodis (ε Aps, ε Apodis) is the Bayer designation for a star in the southern circumpolar constellation of Apus. It has an apparent visual magnitude of 5.06, which is bright enough to be viewed from dark suburban skies. Based upon parallax measurements, it is at a distance of roughly 640 light-years (200 parsecs) from Earth. Based upon a stellar classification of B3 V, this is a massive, B-type main sequence star that is generating energy through the fusion of hydrogen at its core. Epsilon Apodis has more than six times the mass of the Sun and nearly four times the Sun's radius. It is radiating 1,614 times as much luminosity as the Sun from its outer envelope at an effective temperature of 17,050 K. At this heat, it has a blue-white glow that is a characteristic of B-type stars. It is spinning rapidly, with a projected rotational velocity of 255 km/s giving a lower bound for the azimuthal velocity along the equator. Epsilon Apodis is classified as a Gamma Cassiopeiae type variable star and its brightness varies between magnitudes 4.99 and 5.04. In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning
    7.67
    3 votes
    69
    Proxima Centauri

    Proxima Centauri

    • Category: Star
    Proxima Centauri (Latin proxima, meaning "next to" or "nearest to") is a red dwarf star about 4.24 light-years distant in the constellation of Centaurus. It was discovered in 1915 by Robert Innes, the Director of the Union Observatory in South Africa, and is the nearest known star to the Sun, although it is too faint to be seen with the naked eye. Its distance to the second- and third-nearest stars, which form the bright binary Alpha Centauri, is 0.237 ± 0.011 ly (15,000 ± 700 astronomical units [AU]). Proxima Centauri may be part of a triple star system with Alpha Centauri A and B. Because of the proximity of this star, its distance from the Sun and angular diameter can be measured directly, from which it can be determined that its diameter is about one-seventh of that of the Sun. Proxima Centauri's mass is about an eighth of the Sun's, and its average density is about 40 times that of the Sun. Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity. The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total
    7.67
    3 votes
    70
    PSR B1620-26

    PSR B1620-26

    • Category: Star
    PSR B1620-26 is a binary star system located at a distance of 3,800 parsecs (12,400 light-years) in the globular cluster of Messier 4 (M4, NGC 6121) in the constellation of Scorpius. The system is composed of a pulsar (PSR B1620-26 A) and a white dwarf (WD B1620-26 or PSR B1620-26 B). As of 2000, the system is also confirmed to have an extrasolar planet orbiting the two stars. It is theorized that originally PSR B1620−26 A had another, lower mass white dwarf companion, which was ejected when the current PSR B1620−26 B interacted with the original binary system. At that time, PSR B1620−26 B was still a main sequence star, with its planet. Whereupon, the planet settled into orbit around both stars. The triple system is just outside the core of the globular cluster. The age of the cluster has been estimated to be about 12.2 billion years. Hence this is the age estimate for the birth of the planet, and two stars. There is a minor dispute about the proper nomenclature rules to use for this unusual star system. One side regards the A/B convention of naming binary stars as having priority, so that the pulsar is PSR B1620-26 A, the white dwarf companion is PSR B1620-26 B and the planet is
    7.67
    3 votes
    71
    Tau Cassiopeiae

    Tau Cassiopeiae

    • Category: Star
    Tau Cassiopeiae (τ Cas, τ Cassiopeiae) is a star in the constellation Cassiopeia. τ Cassiopeiae is an orange K-type giant with an apparent magnitude of +4.88. It is approximately 172.8 light years from Earth. In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of τ Cassiopeiae, α Lacertae, 4 Lacertae, π Cygni, π Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, τ Cassiopeiae itself is known as 螣蛇十三 (Téng Shé shísān, English: the Thirteenth Star of Flying Serpent)
    7.67
    3 votes
    72
    Theta Aquilae

    Theta Aquilae

    • Category: Star
    Theta Aquilae (θ Aql, θ Aquilae) is a binary star in the constellation Aquila. The combined apparent visual magnitude of the pair is 3.26, making it the fourth brightest member of the constellation. In Chinese, it has the traditional name Tseen Foo, which is derived from the Mandarin 天桴 tiānfú meaning "the heavenly raft(er)"; it may also mean drumsticks, with Altair, Beta Aquilae and Gamma Aquilae being the drum. This distance to this star can be determined through the parallax technique, yielding an estimate of roughly 286 light-years (88 parsecs) from Earth. Theta Aquilae is a double-lined spectroscopic binary, which indicates that the individual components have not been viewed through a telescope; instead, what can be viewed is their combined spectrum with the individual absorption line features shifting back and forth over the course of an orbit because of the Doppler effect. Their orbit has a period of 17.1 days with a large orbital eccentricity is 0.60. At the estimated distance of this system, the angular separation of 3.2 milliarcseconds corresponds to a physical separation of only about 0.24–0.28 Astronomical Units. Both stars have a matching stellar classification of
    7.67
    3 votes
    73
    Zeta Andromedae

    Zeta Andromedae

    • Category: Star
    Zeta Andromedae (Zeta And, ζ Andromedae, ζ And) is a star system in the constellation Andromeda. It is approximately 181 light years from Earth. Zeta Andromedae is an eclipsing spectroscopic binary whose primary is classified as an orange K-type bright giant with a mean apparent magnitude of +4.08. In addition to brightness variation due to eclipses, the system is also an RS Canum Venaticorum type or Beta Lyrae type variable star. Its brightness varies from magnitude +3.92 to +4.14 with a period of 17.77 days. The orbital period of the binary is 17.77 days. This star's location in the constellation Andromeda can be seen in the following diagram: A number of visual companions to the eclipsing binary have been observed. B has common proper motion with A, but C and D are probably optical. In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ζ Andromedae, η Andromedae, 65 Piscium, ε Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, ζ Andromedae itself is known as 奎宿二 (Kuí Sù èr, English: the Second Star of Legs.)
    7.67
    3 votes
    74
    Zeta Leporis

    Zeta Leporis

    • Category: Star
    Zeta Leporis (ζ Lep, ζ Leporis) is a star approximately 70.5 light-years (21.6 parsecs) away in the southern constellation of Lepus. It has an apparent visual magnitude of 3.5, which is bright enough to be seen with the naked eye. In 2001, an asteroid belt was confirmed to orbit the star. Zeta Leporis has a stellar classification of A2 IV-V(n), suggesting that it is in a transitional stage between an A-type main sequence star and a subgiant star. The (n) suffix indicates that the absorption lines in the star's spectrum appear nebulous because it is spinning rapidly, causing the lines to broaden because of the Doppler effect. The projected rotational velocity is 245, giving a lower limit on the star's actual equatorial azimuthal velocity. The star has about 1.46 times the mass of the Sun, along with 1.5 times the radius, and 14 times the luminosity. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is only 17% of the abundance in the Sun. The star appears to be a very young, probably around 231 million years in age, but the margin of error spans 50–347 million years old. In 1983, based on radiation in the infrared portion of the
    7.67
    3 votes
    75
    Chi Aquarii

    Chi Aquarii

    • Category: Star
    Chi Aquarii (χ Aqr, χ Aquarii) is the Bayer designation of a star in the equatorial constellation of Aquarius. The distance to this star, based upon parallax measurements with a 7% margin of error, is roughly 610 light-years (190 parsecs). It is visible to the naked eye with an apparent visual magnitude of +5.06. This is a red giant star with a spectral classification of M3 III. The interferometry-measured angular diameter of this star is 6.70 ± 0.15 mas, which, at its estimated distance, equates to a physical radius of about 137 times the radius of the Sun. It is classified as a semi-regular variable star and its brightness varies by an amplitude of 0.0636 in magnitude. The identified pulsation periods are 32.3, 38.5, and 44.9 days.
    10.00
    1 votes
    76
    Chi Sagittarii

    Chi Sagittarii

    • Category: Star
    The Bayer designation Chi Sagittarii (Chi Sgr, χ Sagittarii, χ Sgr) is shared by three star systems in the constellation Sagittarius. The brightest of these, χ¹ Sagittarii and χ³ Sagittarii, are separated by 0.56° on the sky. The dimmer χ² Sagittarii is located between them, 0.10° from χ¹. The Wow! signal came from the direction of these stars. Chi¹ Sagittarii (Chi¹ Sgr, χ¹ Sagittarii, χ¹ Sgr) is a binary star. The primary is a spectral type A5 dwarf. The companion is approximately 0.12 arcseconds from the primary, putting it about 8 Astronomical Units away. The orbital period is 10.8 years. The combined apparent magnitude of the system is +5.02. It is approximately 220 light years from Earth. Chi² Sagittarii (Chi² Sgr, χ² Sagittarii, χ² Sgr) is a spectral type B7 subgiant which has an apparent magnitude of +7.26. It is approximately 1200 light years from Earth. Chi³ Sagittarii (Chi³ Sgr, χ³ Sagittarii, χ³ Sgr) is a spectral type K3 giant which has an apparent magnitude of +5.45. It is 506 light years from Earth.
    10.00
    1 votes
    77
    Gamma Arae

    Gamma Arae

    • Category: Star
    Gamma Arae (γ Ara, γ Arae) is a star in the southern constellation of Ara. With an apparent visual magnitude of 3.3, it is the fourth brightest star in the constellation and is readily visible to the naked eye. From parallax measurements made during the Hipparcos mission, the distance to this star can be estimated as 1,110 light-years (340 parsecs) from Earth. This is an enormous star with 23 times the radius of the Sun. It is radiating 120,000 as much energy as the Sun from its outer envelope at an effective temperature of 21,500 K. This heat gives the star the blue-white glow of a B-type star. The spectrum shows it to match a stellar classification of B1 Ib, with the luminosity class of 'Ib' indicating this is a lower luminosity supergiant star. It is a relatively young body, with an estimated age of around 15.7 million years. Gamma Arae is rotating rapidly with a projected rotational velocity of 269 km s, causing it to complete a full rotation about every 4.8 days. In the spectrum of this star, this high rate of spin is causing absorption lines to blend together because of the Doppler effect, making them more difficult to analyze. It is a periodically variable star that
    10.00
    1 votes
    78
    GCRT J1745-3009

    GCRT J1745-3009

    • Category: Star
    GCRT J1745-3009 is a newly discovered transient, bursting low-frequency radio source which lies in the direction of the galactic center. A group of astronomers from Sweet Briar College and the Naval Research Laboratory detected transient emission from two sources in 1998 while studying the Galactic Center. They then began monitoring the region specifically looking for transient sources and detected five bursts of radio waves about 1 meter in wavelength (frequency 330 MHz) during a seven-hour period from September 30 to October 1, 2002. The five bursts were of equal brightness, with each lasting about 10 minutes, and occurring every 77 minutes. Like an earlier low-frequency transient discovered by the same group, it was given the designation GCRT, an abbreviation for Galactic Center Radio Transient. The source was also nicknamed a burper. The group found no X-ray or γ-ray counterpart to the object. Another burst from the source was later found in data recorded September 28, 2003, and a weaker burst was found in data recorded March 20, 2004. As of January 2007, no other bursts have been found. The discoverers argue that if the source is further than 70 parsecs away, its high
    10.00
    1 votes
    79
    Kappa Cassiopeiae

    Kappa Cassiopeiae

    • Category: Star
    Kappa Cassiopeiae (κ Cas, κ Cassiopeiae) is a star in the constellation Cassiopeia. κ Cassiopeiae is a blue-white B-type supergiant with a mean apparent magnitude of +4.17. It is approximately 4100 light years from Earth. It is classified as an Alpha Cygni type variable star and its brightness varies from magnitude +4.22 to +4.30.
    10.00
    1 votes
    80
    Theta Antliae

    Theta Antliae

    • Category: Star
    Theta Antliae (θ Ant, θ Antliae) is the Bayer designation for a binary star in the southern constellation of Antlia. The pair have a combined apparent visual magnitude of +4.78; the brighter component is magnitude +5.30 while the secondary is +6.18. Based upon parallax measurements, it is located at a distance of around 340 light-years (100 parsecs) from Earth. The primary component of this system, θ Ant A, has a stellar classification of A8 Vm, indicating that it is an A-type main sequence star with enhanced metallic lines in its spectrum. The companion, θ Ant B, is a giant star with a classification of G7 III. The pair have an orbital period of 18.3 years, a significant eccentricity of 0.445, and they have an angular separation of 0.1 arcseconds.
    10.00
    1 votes
    81
    Upsilon Andromedae

    Upsilon Andromedae

    • Category: Star
    Upsilon Andromedae (υ Andromedae, υ And) is a binary star located approximately 44 light-years away from Earth in the constellation Andromeda. The primary star (Upsilon Andromedae A) is a yellow-white dwarf star that is somewhat younger than the Sun. The second star in the system (Upsilon Andromedae B) is a red dwarf located in a wide orbit. As of 2010, four confirmed extrasolar planets are known in orbit around the primary star. All four are likely to be jovian planets that are comparable to Jupiter. Upsilon Andromedae was both the first multiple-planet planetary system to be discovered around a main sequence star, and the first multiple-planet system known in a multiple star system. Upsilon Andromedae A was ranked 21st in the list of top 100 target stars for the NASA Terrestrial Planet Finder mission, which has, however, been reported to have been cancelled as of 2011. Upsilon Andromedae is located fairly close to the Solar System: the parallax of Upsilon Andromedae A was measured by the Hipparcos astrometry satellite as 74.12 milliarcseconds, corresponding to a distance of 13.49 parsecs (44 light years). Upsilon Andromedae A has an apparent magnitude of +4.09, making it visible
    10.00
    1 votes
    82
    Zeta Cassiopeiae

    Zeta Cassiopeiae

    • Category: Star
    Zeta Cassiopeiae (ζ Cas, ζ Cassiopeiae) is a star in the constellation Cassiopeia. It has a blue-white hue and is classified as a B-type subgiant with an apparent magnitude of +3.67. It is approximately 590 light years from Earth. ζ Cas is a member of an unusual group of variable stars known as "Slowing Pulsating B" (SPB) stars. It shows a pulsation frequency of 0.64 per day (or once every 1.56 days) and displays a weak magnetic field with a strength of roughly 3.35 × 10 T, which varies with a period of 5.37 days. This likely matches the rotation rate of the star, which, when combined with the low projected rotational velocity, indicates the star may be seen nearly pole-on. Zeta Cassiopeiae is a candidate magnetic Bp star that shows an overabundance of helium. The star contains a randomly oriented fossil magnetic field, which impacts the outflow of the stellar wind. Collisions between streams from this stellar wind creates a shock front, with cooling particles settling toward a co-rotating disk. In Chinese astronomy, Zeta Cassiopeiae is called 附路, Pinyin: Fùlù, meaning Auxiliary Road, because this star is marking itself and stand alone in Auxiliary Road asterism, Legs (mansion)
    10.00
    1 votes
    83
    Gamma Cassiopeiae

    Gamma Cassiopeiae

    • Category: Star
    Gamma Cassiopeiae (γ Cas, γ Cassiopeiae) is the Bayer designation for a star in the northern circumpolar constellation of Cassiopeia. Although it is a fairly bright star with an apparent visual magnitude of 2.47, it has no traditional Arabic or Latin name. However, in Chinese, it has the name Tsih, derived from the word 策 (cè), meaning "the whip". It is located at the center of the distinctive "W" shape that forms the constellation's asterism. American astronaut Virgil Ivan "Gus" Grissom nicknamed the star Navi after his own middle name spelled backwards. The star was used as an easily identifiable navigational reference point during space missions. Based upon parallax measurements made by the Hipparcos satellite, this star is located at a distance of roughly 550 light-years (170 parsecs) from Earth. This is an eruptive variable star, whose brightness changes irregularly between +2.20 mag and +3.40 mag. It is the prototype of the class of Gamma Cassiopeiae variable stars. The apparent magnitude of this star was +2.2 in 1937, +3.4 in 1940, +2.9 in 1949, +2.7 in 1965 and now it is +2.15. At maximum intensity, γ Cassiopeiae outshines both α Cassiopeiae (magnitude +2.25) and β
    6.50
    4 votes
    84
    Juxta Crucem

    Juxta Crucem

    • Category: Star
    Epsilon Crucis (ε Cru, ε Crucis) is a Class K3III, fourth-magnitude star in the constellation Crux. It is sometimes called Intrometida (intrusive) in Portuguese. This star is an orange giant, located about 228 light-years from Earth. ε Cru is represented on the flags of Australia and Papua New Guinea, as one of five stars which comprise the Southern Cross. It is also featured in the flag of Brazil, along with 26 other stars, each of which represents a state. ε Cru represents the State of Espírito Santo.
    6.50
    4 votes
    85
    Pleione

    Pleione

    • Category: Star
    Pleione (28 Tauri, BU Tauri) is a binary star in the Pleiades star cluster (M45), located roughly 390 light years away in the constellation of Taurus. Pleione was not given a Bayer designation, but did receive a Flamsteed number—hence its designation 28 Tauri. Since the star is located close to Atlas, it's difficult for stargazers to distinguish with the naked eye, even though it's a hot type B star 190 times more luminous than the Sun. Pleione rotates even faster than Achernar on its axis, close to its breakup velocity. The brighter star of the binary pair, component A, is a classical Be star with certain distinguishing traits: periodic phase changes and a complex circumstellar environment composed of two gaseous disks at different angles to each other. Although some research on the system has been performed, stellar characteristics of the orbiting B component are not well known. Pleione is the seventh brightest star in the Pleiades, after Taygeta. With an apparent magnitude of +5.05 in V, the star is rather difficult to make out with the naked eye, especially since its close neighbour Atlas is 3.7 times brighter and located less than 5 arcminutes away. Beginning in October of
    6.50
    4 votes
    86
    Alpha Crucis

    Alpha Crucis

    • Category: Star
    Alpha Crucis (α Cru, α Crucis, also Acrux, HD 108248) is the brightest star in the constellation Crux, the Southern Cross, and, at a combined visual magnitude 0.77, is the twelfth brightest star in the night sky. Acrux is the southernmost first-magnitude star, just a bit more southerly than Alpha Centauri. Acrux is a multiple star system located 321 light years from the solar system. Only two components are visually distinguishable, α and α, separated by 4 arcseconds. α is magnitude 1.40 and α is magnitude 2.09, both hot class B (almost class O) stars, with surface temperatures of about 28,000 and 26,000 K respectively. Their luminosities are 25,000 and 16,000 times that of the Sun. α and α orbit over such a long period that motion is only barely seen. From their minimum separation of 430 astronomical units, the period is at least 1,500 years, and may be much longer. α is itself a spectroscopic binary star, with its components thought to be around 14 and 10 times the mass of the Sun and orbiting in only 76 days at a separation of about 1 AU. The masses of α and the brighter component of α suggest that the stars will someday explode as supernovae. The fainter component of α may
    8.50
    2 votes
    87
    Chi Cassiopeiae

    Chi Cassiopeiae

    • Category: Star
    Chi Cassiopeiae (χ Cas, χ Cassiopeiae) is a star in the constellation Cassiopeia. χ Cassiopeiae is a yellow G-type giant with an apparent magnitude of +4.68. It is approximately 204.4 light years from Earth.
    8.50
    2 votes
    88
    Gliese 436

    Gliese 436

    • Category: Star
    Gliese 436 is a red dwarf star approximately 33.1 light-years (10.1 parsecs) away in the zodiac constellation of Leo. It has an apparent visual magnitude of 10.67, which is much too faint to be seen with the naked eye. However, it can be viewed with even a modest telescope of 2.4 in (6 cm) aperture. In 2004, the existence of an extrasolar planet, Gliese 436b, was verified as orbiting the star. In 2012, the existence of a second planet, UCF-1.01, was also verified. The spectrum of this star indicates it a M2.5 V star, which places it among a populous group of low-mass stars known as red dwarfs. The luminosity class of 'V' indicates it is a main sequence star that is generating energy by the nuclear fusion of hydrogen at its core region. Stellar models for this star give an estimated size of about 42% of the Sun's radius. The same model predicts the outer atmosphere has a low effective temperature of 3,318 K, giving it the orange-red hue of an M-type star. Small stars such as this generate energy at a low rate, giving it only 2.5% of the Sun's luminosity. Gl 436 is older than the Sun by several billion years and it has an abundance of heavy elements (with masses greater than
    8.50
    2 votes
    89
    Mu Herculis

    Mu Herculis

    • Category: Star
    Mu Herculis is a nearby star system about 27.1 light years from Earth in the constellation Hercules. Its main star, Mu Herculis A is fairly similar to the Sun although more highly evolved with a stellar classification of G5 IV. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Its mass is about 1.1 times that of the Sun, and it is beginning to expand to become a giant. The secondary component consists of a pair of stars that orbit about each other with a period of 43.2 years. Mu Herculis A and the binary pair B-C are separated by 286 AUs. The stars B-C are separated from each other by 11.4 AUs. Their orbit is quite elliptic (e=0.18) and both stars swing each other between 9.4 and 13.5 AUs. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Marfak Al Jathih Al Aisr, which was translated into Latin as Cubitum Sinistrum Ingeniculi, meaning the left elbow of kneeling man. In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the left borderline of the
    8.50
    2 votes
    90
    Procyon

    Procyon

    • Category: Star
    Procyon (α CMi, α Canis Minoris, Alpha Canis Minoris) is the brightest star in the constellation Canis Minor. To the naked eye, it appears to be a single star, the seventh brightest in the night sky with a visual apparent magnitude of 0.34. It is actually a binary star system, consisting of a white main-sequence star of spectral type F5 IV–V, named Procyon A, and a faint white dwarf companion of spectral type DA, named Procyon B. The reason for its brightness is not its intrinsic luminosity but its closeness to the Sun; as determined by the Hipparcos astrometry satellite, it lies at a distance of just 11.46 light-years (3.51 parsecs), and is therefore one of our nearest stellar neighbours. Its closest neighbour is Luyten's Star, about 1.12 ly (0.34 pc) away, and the latter would appear as a visual magnitude −7 star in the night sky of a hypothetical planet orbiting Procyon. Procyon forms one of the three vertices of the Winter Triangle, along with Sirius and Betelgeuse. Its color index is 0.42, and its hue has been described as having a faint yellow tinge to it. Procyon A has a stellar classification of F5IV–V. The effective surface temperature of the star is an estimated 6,530 K,
    8.50
    2 votes
    91
    Sigma Cassiopeiae

    Sigma Cassiopeiae

    • Category: Star
    Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is approximately 1520 light years from Earth and is a combined apparent magnitude of +4.88. The primary component, σ Cassiopeiae A, is a blue-white B-type giant with an apparent magnitude of +5.0. Its companion, σ Cassiopeiae B, is a blue-white B-type main sequence dwarf, with an apparent magnitude of +7.1. The two stars are 3.1 arcseconds apart. In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of σ Cassiopeiae, α Lacertae, 4 Lacertae, π Cygni, π Cygni, HD 206267, ε Cephei, β Lacertae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, σ Cassiopeiae itself is known as 螣蛇十一 (Téng Shé shíyī, English: the Eleventh Star of Flying Serpent)
    8.50
    2 votes
    92
    Tau Canis Majoris

    Tau Canis Majoris

    • Category: Star
    Tau Canis Majoris (τ CMa, τ Canis Majoris) is an eclipsing spectroscopic binary in the constellation Canis Major and the brightest star of an open cluster designated NGC 2362. It is approximately 3200 light years from Earth. This star is sometimes known as the 'Mexican Jumping Star' by amateur astronomers, because it can appear to 'jump around' with respect to the other stars in the cluster because of its marked contrast in brightness. τ Canis Majoris is classified as an O-type blue supergiant with a mean apparent magnitude of +4.37. It is a Beta Lyrae type variable star with a period of 1.28 days, over which time its brightness varies from magnitude +4.32 to +4.37.
    8.50
    2 votes
    93
    U Geminorum

    U Geminorum

    • Category: Star
    U Geminorum (U Gem), in the constellation Gemini, is an archetypal example of a dwarf nova. The binary star system consists of a white dwarf closely orbiting a red dwarf. Roughly every 100 days it undergoes an outburst that greatly increases its brightness. Discovered by J.R. Hind in 1855 during one of its outbursts, it has been continuously observed since. The U Geminorum binary has a very short orbital period of 4 hours and 11 minutes; this orbit alone makes the system variable, as the components transit and eclipse each other with each revolution. Normally, the combined apparent magnitude varies between 14.0 and 15.1; during an outburst however, the star can brighten a hundredfold, to 9th magnitude. Though the average interval is 100 days, the period is in fact highly irregular, varying from as little as 62 days to as long as 257. As is the case with dwarf novae, the outbursts are theorized results of a periodic surge of influx from the white dwarf's accretion disk, caused by instability in the disk itself. Distance estimates for U Geminorum have varied from 52 parsecs (170 light-years) to 112 parsecs (370 light-years), with a best estimate of 82 parsecs (270 light-years).
    8.50
    2 votes
    94
    Uranus

    Uranus

    • Category: Planet
    Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus (Ancient Greek: Οὐρανός), the father of Cronus (Saturn) and grandfather of Zeus (Jupiter). Though it is visible to the naked eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the Solar System for the first time in modern history. Uranus was also the first planet discovered with a telescope. Uranus is similar in composition to Neptune, and both are of different chemical composition than the larger gas giants, Jupiter and Saturn. Astronomers sometimes place them in a separate category called "ice giants". Uranus's atmosphere, while similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, contains more "ices" such as water, ammonia and methane, along with traces of hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C).
    8.50
    2 votes
    95
    Fomalhaut

    Fomalhaut

    • Category: Star
    Fomalhaut (Alpha Piscis Austrini, Alpha PsA, α Piscis Austrini, α PsA) is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings. Near latitude 50˚N, it sets around the time Sirius rises, and does not reappear until Antares sets. Its name derives from Arabic fum al-ḥawt, meaning "mouth of the [Southern] Fish" (فُمْ اَلْحَوْتْ). This is a class A star on the main sequence approximately 25 light-years (7.7 pc) from Earth as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. Fomalhaut and the K-type star TW Piscis Austrini constitute a binary system. Fomalhaut holds a special significance in extrasolar planet research, as it is the center of the first stellar system with an extrasolar planet (Fomalhaut b) imaged at visible wavelengths. The image was published in Science in November 2008. It is
    7.33
    3 votes
    96
    HD 107146

    HD 107146

    • Category: Star
    HD 107146 is a star in the constellation Coma Berenices that is located about 90 light years from Earth. The apparent magnitude of 7.028 makes this star too faint to be seen with the unaided eye. The physical properties of this star are similar to the Sun, including the stellar classification G2V, making this a solar analog. The mass of this star is about 109% of the solar mass and it has about 99% the radius of the Sun. It is a young star with an age between 80 and 200 Myr. The axis of rotation is estimated at 21+8 −9 degrees to the line of sight and it completes a rotation in a relatively brief 3.5 days. In 2003, astronomers recognized the excess infrared and submillimeter emission indicative of circumstellar dust, the first time such a debris disk phenomenon was noted around a star of similar spectral types as the Sun, though having a much younger age. In 2004 the Hubble Space Telescope detected the presence of a spatially resolved disc surrounding the star The star's circumstellar disc has dimensions of approximately 210 x 300 AU. The dusty ring is cool, with a temperature of 51 K, and has a mass of 0.10 M⊕. Analysis of the debris disk in the far-infrared and submillimeter
    7.33
    3 votes
    97
    HD 189733

    HD 189733

    • Category: Star
    HD 189733, also catalogued as V452 Vulpeculae, is a binary star system approximately 63 light-years away in the constellation of Vulpecula (the Fox). The primary star is suspected to be an orange dwarf star, while the secondary star is a red dwarf star. Given that this system has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula (M27). As of 2005, it has been confirmed that an extrasolar planet orbits the primary star within the system. HD 189733 A is an orange dwarf star of the spectral type K1.5V. The star has a mass of 82 percent that of the Sun, a radius 75 percent, and a luminosity of 26.4 percent. The star is between 89 and 102 percent as enriched in iron as the Sun, making the star more than 600 million years old. The star has starspots which affect its luminosity by 1.5 percent in visible light. As a result, it is listed in the General Catalogue of Variable Stars as a BY Draconis variable with the variable star designation V452 Vul. Discovered in 2006 by the infrared 2MASS astronomical survey, 2MASS J20004297+2242342 or HD 189733 B is a
    7.33
    3 votes
    98
    Maia

    Maia

    • Category: Star
    Maia (20 Tauri) is a star in the constellation Taurus. It is the fourth brightest star in the Pleiades open star cluster (M45), after Alcyone, Atlas and Electra, in that order. The name Maia originates with the Greek: Μαῖα and Latin: Maia. She is one of the seven daughters of Atlas and Pleione in Greek mythology—stars which are also included in the Pleaides star cluster (see map). Maia is a blue giant of spectral type B8 III, and a mercury-manganese star. Maia's visual magnitude is 3.871, requiring darker skies to be seen. Its total bolometric luminosity is 660 times solar, mostly in the ultraviolet, thus suggesting a radius that is 5.5 times that of the Sun and a mass that is slightly more than 4 times solar. Maia is one of the stars in the Maia Nebula (also known as NGC 1432), a bright emission or reflection nebula within the Pleiades star cluster. Maia was thought to be a variable star by astronomer Otto Struve. A class of stars known as Maia variables was proposed, which included Gamma Ursae Minoris, but Maia and some others in the class have since been found to be stable. Maia was the oldest of seven beautiful sisters known as the Pleiades. She was raped by Zeus, thereby
    7.33
    3 votes
    99
    Mizar

    Mizar

    • Category: Star
    The Mizar–Alcor stellar sextuple system consists of the quadruple system Mizar and the binary system Alcor. Mizar (Zeta Ursae Majoris, Zeta UMa, ζ Ursae Majoris, ζ UMa) is a quadruple system of two binary stars in the constellation Ursa Major and is the second star from the end of the Big Dipper's handle. Its apparent magnitude is 2.23 and its spectral class is A1V. Mizar's name comes from the Arabic مئزر mīzar, meaning a waistband or girdle. With normal eyesight one can make out a faint companion just to the east, named Alcor or 80 Ursae Majoris. Alcor is of magnitude 3.99 and spectral class A5V. Mizar and Alcor together are sometimes called the "Horse and Rider," and the ability to resolve the two stars with the naked eye is often quoted as a test of eyesight, although even people with quite poor eyesight can see the two stars. Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. Astronomer Sir Patrick Moore has suggested that this in fact refers to another star which lies visually between Mizar and Alcor. The name the Arabs used for Alcor was سها (suha), meaning either the ‘forgotten’ or ‘neglected’ one. As of 2007, the best estimates
    7.33
    3 votes
    100
    Pluto

    Pluto

    • Category: Dwarf planet
    Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System (after Eris) and the tenth-most-massive body observed directly orbiting the Sun. Originally classified as the ninth planet from the Sun, Pluto was recategorized as a dwarf planet and plutoid owing to the discovery that it is only one of several large bodies within the Kuiper belt. Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small, approximately one-sixth the mass of the Earth's Moon and one-third its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto to periodically come closer to the Sun than Neptune. As of 2011, it is 32.1 AU from the Sun. From its discovery in 1930 until 2006, Pluto was classified as a planet. In the late 1970s, following the discovery of minor planet 2060 Chiron in the outer Solar System and the recognition of Pluto's relatively low mass, its status as a major planet began to be questioned. In the late 20th and early 21st centuries, many objects similar to Pluto were discovered in the outer Solar System, notably the
    7.33
    3 votes
    101
    Zeta Orionis

    Zeta Orionis

    • Category: Star
    Alnitak (Arabic: النطاق an-niṭāq‎) is a triple star some 736 light years distant in the constellation Orion. It is part of Orion's Belt along with Alnilam and Mintaka, and has a Bayer designation of Zeta Orionis. The primary star is a hot blue supergiant with an absolute magnitude of -5.25, and is the brightest class O star in the night sky with a visual magnitude of +2.04. It has two bluish 4th magnitude companions, producing a combined magnitude for the trio of +1.72. The stars are members of the Orion OB1 association and the Collinder 70 association. Alnitak has been known since antiquity and, as a component of Orion's belt, has been of widespread cultural significance. It was reported to be a double star by amateur German astronomer George K. Kunowsky in 1819. Much more recently, in 1998, the bright primary was found by a team from the Lowell Observatory to have a close companion; this had been suspected from observations made with the Narrabri Stellar Intensity Interferometer in the 1970s. Initially thought to be around 1500 light years distant, the Alnitak system's distance was determined to be roughly half that via measurement of its stellar parallax by the Hipparcos
    7.33
    3 votes
    102
    3C58

    3C58

    • Category: Star
    3C58 or 3C 58 is a pulsar and supernova remnant within the Milky Way that is possibly associated with the supernova SN 1181. There are, however, signs that indicate that it could be several thousand years old, and thus not associated with that supernova. 3C58 is notable for its very high rate of cooling which is unexplained by standard theories of neutron star formation. It is hypothesized that extreme conditions in the star's interior cause a high neutrino flux, which carries away the energy and the star cools. It is located in the direction of Cassiopeia and is estimated to be 10,000 light-years away. 3C58 has been proposed as a possible quark star. Media related to 3C 58 at Wikimedia Commons
    6.25
    4 votes
    103
    54 Piscium

    54 Piscium

    • Category: Star
    54 Piscium is an orange dwarf star approximately 36 light-years away in the constellation of Pisces. In 2002, an extrasolar planet was confirmed to be orbiting the star, and in 2006, a brown dwarf was also discovered orbiting it. The Flamsteed designation 54 Piscium originated in the star catalogue of the British astronomer John Flamsteed, first published in 1712. It has an apparent magnitude of 5.86, allowing it to be seen with the unaided eye under suitable viewing conditions.The star has a classification of K0V, with the luminosity class V indicating this is a main sequence star that is generating energy at its core through the thermonuclear fusion of hydrogen into helium. The effective temperature of the photosphere is about 5,062 K, giving it the characteristic orange hue of a K-type star. It has been calculated that the star may have 76 percent of the Sun's mass and 46 percent of the luminosity. The radius has been directly determined by interferometry to be 94 percent that of the Sun's radius using the CHARA array. The rotational period of 54 Piscium is about 40.2 days. The age of the star is about 6.4 billion years, based on chromospheric activity and isochronal analysis.
    6.25
    4 votes
    104
    Crab Pulsar

    Crab Pulsar

    • Category: Star
    The Crab Pulsar (PSR B0531+21) is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054. Discovered in 1968, the pulsar was the first to be connected with a supernova remnant. The optical pulsar is roughly 25 km in diameter and the pulsar "beams" rotate once every 33 milliseconds, or 30 times each second. The outflowing relativistic wind from the neutron star generates synchrotron emission, which produces the bulk of the emission from the nebula, seen from radio waves through to gamma rays. The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the surrounding nebula, forming a termination shock. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar into the main body of the nebula. The period of the pulsar's rotation is slowing by 38 nanoseconds per day due to the large amounts of energy carried away in the pulsar wind. The Crab Nebula is often used as a calibration
    6.25
    4 votes
    105
    Gliese 876

    Gliese 876

    • Category: Star
    Gliese 876 is a red dwarf star approximately 15 light-years away from Earth in the constellation of Aquarius. It is the third closest known star to the Sun confirmed to possess a planetary system (after Gliese 674 and Epsilon Eridani) and the closest such system known to consist of multiple planets. As of 2011, four extrasolar planets have been found to orbit the star. The planetary system is also notable for the orbital properties of its planets. It is the only known system of orbital companions to exhibit a triple conjunction in the rare phenomenon of Laplace resonance (a type of resonance first noted in Jupiter's inner three Galilean moons). It is also the first extrasolar system around a normal star with measured coplanarity. Two of the middle planets are located in the system's habitable zone, however they are giant planets believed to be analogous to Jupiter. Gliese 876 is located fairly close to the Solar System. According to astrometric measurements made by the Hipparcos satellite, the star shows a parallax of 213.28 milliarcseconds, which corresponds to a distance of 4.69 parsecs (15.3 ly), currently making it the third closest known star with orbiting planets, after
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    106
    HD 188753

    HD 188753

    • Category: Star
    HD 188753 is a hierarchical triple star system approximately 151 light-years away in the constellation of Cygnus, the Swan. In 2005, an extrasolar planet was announced to be orbiting the primary star (designated HD 188753 A) in the system. Follow-up measurements by an independent group in 2007 did not confirm the planet's existence. The primary star, HD 188753 A, is similar to the Sun with a mass only 6% larger and a stellar classification of G8V. Orbiting this primary at a distance of 12.3 AU is a pair of smaller stars that orbit each other with a period of 156.0 ± 0.1 days, a semi-major axis of 0.67 AU, and eccentricity of 0.1 ± 0.03. The pair have a estimated masses of 0.96 and 0.67 solar masses. They orbit the primary with a period of about 25.7 years and an orbital eccentricity of about 0.50. The periastron distance of this orbit is 6.2 AU. In 2005 the discovery of a candidate planet orbiting the primary star of the triple star system was announced. This planet, which received the designation HD 188753 Ab, was announced by a Polish astronomer working in the United States, Dr. Maciej Konacki. This would not be the first known planet in a triple star system – for example, the
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    4 votes
    107
    LBV 1806-20

    LBV 1806-20

    • Category: Star
    LBV 1806-20 is a luminous blue variable (LBV) and likely binary star located nearly 40,000 light-years from the Sun, towards the center of the galaxy. It has a total system mass of around 130 solar masses and an estimated variable luminosity of around two million times that of the Sun. Despite its high luminosity, it is virtually invisible from the Solar System, because less than one billionth of its visible light reaches us, the rest being absorbed by intervening interstellar gas and dust. Although the star is 8th magnitude at the near infrared wavelength of 2 micrometers, it is calculated to be about 35th magnitude at visible wavelengths, which is undetectable. When first discovered, LBV 1806-20 was considered both the most luminous and most massive star known, challenging our understanding of the formation of massive stars. Recent estimates placing it somewhat nearer to the earth and also its binary nature mean that it is now well within the expected range of parameters for the most luminous stars in the galaxy. LBV 1806-20 lies at the core of radio nebula G10.0-0.3 and is a component of the star cluster Cl* 1806-20, itself a component of W31, one of the largest H II regions in
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    4 votes
    108
    51 Pegasi

    51 Pegasi

    • Category: Star
    51 Pegasi (abbreviated 51 Peg) is a Sun-like star located 50.9 light-years (15.6 parsecs) from Earth in the constellation Pegasus. It was the first extrasolar Sun-like star found to have a planet orbiting it. The star is of apparent magnitude 5.49, and so is visible with the naked eye under suitable viewing conditions. The Flamsteed designation for this star, 51 Pegasi, was assigned by John Flamsteed in his star atlas published in 1712. 51 Pegasi has a stellar classification of G5V, indicating that it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The effective temperature of the chromosphere is about 5571 K, giving 51 Pegasi the characteristic yellow hue of a G-type star. It is estimated to be 6.1–8.1 billion years old, somewhat older than the Sun, with a radius 24% larger and 11% more massive. The star has a higher proportion of elements other than hydrogen/helium compared to the Sun; a quantity astronomers term a star's metallicity. Stars with higher metallicity such as this are more likely to host planets. In 1996 astronomers Baliunas, Sokoloff, and Soon measured a rotational period of 37 days for 51 Pegasi. Although
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    3 votes
    109
    Alpha Librae

    Alpha Librae

    • Category: Star
    Alpha Librae (α Lib, α Librae) is the Bayer designation for the second brightest star in the constellation Libra (despite its Bayer designation as alpha). It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي (al-zuban al-janūbiyy), means "southern claw" and was coined before Libra was recognized as distinct from Scorpius. The alternate names Kiffa Australis and Elkhiffa Australis, partial Latin translations of Arabic al-kiffah al-janūbiyy, mean "southern pan (of the scales)". Another name used in older astronomy texts, equivalent to "southern scale or pan", was Lanx Australis. Alpha Librae is close to the ecliptic so it can be easily occulted by the Moon and (very rarely) by planets. The next occultation by a planet will be by Mercury on 10 November 2052. Alpha Librae is located approximately 77 light years from the Sun. The two brightest components of Alpha Librae form a double star that share a similar motion through space, forming common proper motion companions. The brightest member, α Librae, is itself a spectroscopic binary system. The second member, α Librae, is separated from the primary system by around 5,400 AU. It too is a spectroscopic binary
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    3 votes
    110
    Gamma Andromedae

    Gamma Andromedae

    • Category: Star
    Gamma Andromedae (Gamma And, γ And, γ Andromedae) is the third brightest star in the constellation of Andromeda. It is also known by the traditional name Almach (also spelt as Almaach, Almaack, Almak, Almaak, or Alamak). In 1778, Johann Tobias Mayer discovered that γ Andromedae was a double star. When examined in a small telescope, it appears to be a bright, golden yellow star (γ Andromedae) next to a dimmer, indigo blue star (γ Andromedae), separated by approximately 10 arcseconds. It is considered by stargazers to be a beautiful double star with a striking contrast of color. It was later discovered that γ Andromedae is itself a triple star system. What appears as a single star to the naked eye is thus a quadruple star system, approximately 350 light-years from the Earth. γ Andromedae is a bright giant star with a spectral classification of K3IIb. It has an apparent visual magnitude of approximately 2.26. γ Andromedae, with an overall apparent visual magnitude of 4.84, is 9.6 arcseconds away from γ Andromedae at a position angle of 63 degrees. In October 1842, Wilhelm Struve found that γ Andromedae was itself a double star whose components were separated by less than an arcsecond.
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    3 votes
    111
    OTS 44

    OTS 44

    • Category: Star
    OTS 44 is a sub-stellar object known as a brown dwarf, located about 550 light-years (170 pc) away in constellation Chamaeleon. It is among the smallest known brown dwarfs, with about 15 times the mass of Jupiter, or about 1.5% that of the Sun. Its radius is about 23% of the Sun's. This brown dwarf is located in the star-forming region Chamaeleon I. Based upon infrared observations with the Spitzer Space Telescope, OTS 44 emits an excess of infrared radiation for an object of its type, suggesting it has a circumstellar disk of dust and particles of stone and ice. This disk has an inner radius roughly three times the radius of OTS 44 and is accreting matter at the rate of about 10 the mass of the Sun per year. It could eventually develop into a planetary system.
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    3 votes
    112
    R Horologii

    R Horologii

    • Category: Star
    R Horologii (also known as HD 18242) is a red giant star approximately 100 light-years away in the constellation Horologium. It is also a Mira variable with a period of 407.6 days, and has one of the largest magnitude ranges known (from 4.7 to 14.3).
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    3 votes
    113
    Zeta Tucanae

    Zeta Tucanae

    • Category: Star
    Zeta Tucanae (ζ Tuc, ζ Tucanae) is a star in the constellation Tucana. It is a spectral class F9.5 main sequence star with an apparent magnitude of +4.23. Despite having a slightly lower mass, this star is more luminous than the Sun. Based upon parallax measurements by the Hipparcos spacecraft, it is approximately 28.0 light years from Earth. This is one of the least variable stars observed during the Hipparcos mission. The composition and mass of this star are very similar to the Sun, with a slightly lower mass and an estimated age of three billion years. The solar-like qualities make it a target of interest for investigating the possible existence of a life-bearing planet. Based upon an excess emission of infrared radiation at 70 micrometres, this system is believed to have a debris disk. The disk is orbiting the star at a minimum radius of 2.3 astronomical units. It is radiating with a maximum temperature of 218 K. As of 2009, no planet has been discovered in orbit around this star. The components of this star's space velocity are U = −60, V = −4 and W = −38 km/s. These correspond to the velocity toward the galactic center, the velocity along the direction of galactic rotation,
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    3 votes
    114
    Zeta Boötis

    Zeta Boötis

    • Category: Star
    Zeta Boötis (ζ Boo, ζ Boötis) is a binary star system in the constellation of Boötes that consists of two giant stars with matching stellar classifications of A2III. They have the Flamsteed designation 30 Boötis. This system is approximately 180 light years from Earth and has a combined apparent magnitude of +3.78. The individual magnitudes differ slightly, with component A having a magnitude of 4.43 and component B at the slightly dimmer magnitude 4.83. The binary nature of this system has been tracked since 1796. They complete an orbit roughly every 45,460 days, or 124.46 years. The next close approach will occur during August 2023. The orbit of this pair has a very high eccentricity of 0.9977, bringing the stars within 0.3 AU at their closest approach.
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    4 votes
    115
    Beta Ophiuchi

    Beta Ophiuchi

    • Category: Star
    Beta Ophiuchi (β Oph, β Ophiuchi) is a star in the equatorial constellation of Ophiuchus. It has the traditional names Celbalrai, which comes from the Arabic كلب الراعي kalb al-rā‘ī meaning "shepherd dog". It is also called Cheleb, Kelb Alrai, or sometimes just Alrai. the apparent visual magnitude of this star is 2.7, which is readily visible to the naked eye even from urban skies. The distance to this star can be estimated using parallax measurements, yielding a value of 81.8 light-years (25.1 parsecs). This is a giant star with a stellar classification of K2 III. Although it is only 13% greater in mass than the Sun, it has reached a stage in its evolution where the atmosphere has expanded to about 12 times the Sun's radius and is radiating 63 times the luminosity of the Sun. Its outer envelope is relatively cool with an effective temperature of 4,467 K, giving it the orange hue typical of K-type stars. Like some other K-type giants, β Ophiuchi has been found to vary very slightly (0.02 magnitudes) in brightness. Cebalrai is a member of the thin disk population. It is following a low eccentricity orbit through the Milky Way galaxy that carries it between a distance of 27.3–30.9
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    116
    Beta Scorpii

    Beta Scorpii

    • Category: Star
    Beta Scorpii (β Sco, β Scorpii) is a multiple star system in the southern zodiac constellation of Scorpius. It has the traditional names Acrab, Akrab or Elacrab, all come from (Arabic: العقرب‎) al-'Aqrab, the Scorpion, for the whole constellation, as well as Graffias, a name it shares with Xi Scorpii. It was known as 房宿四 (the Fourth Star of the Room) in Chinese. Observed through a small telescope, Beta Scorpii appears as a binary star with a separation between the two components of 13.5 arcseconds. This pair, β and β, form the top branches of the hierarchy of orbiting components in this system. β Scorpii, the brighter of the pair, consists of two sub-components, β Sco A and β Sco B, orbiting at an angular separation of 3.9 arcseconds with an orbital period of 610 years. β Sco A is itself a spectroscopic binary with the components β Sco Aa and β Sco Ab separated by 1.42 milliarcseconds and an orbital period of 6.82 days. The second visual component, β Scorpii, has two sub-components, β Sco C and β Sco E, orbiting at an angular separation of 0.1328 arcseconds with an orbital period of 39 years. β Sco E is a spectroscopic binary with the components β Sco Aa and β Sco Ab having an
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    2 votes
    117
    Delta Orionis

    Delta Orionis

    • Category: Star
    Mintaka (δ Orionis, 34 Orionis) is a star some 900 light years distant in the constellation Orion. The name Mintaka comes from منطقة manţaqah, which means "the belt" in Arabic. Together with Alnitak (Zeta Orionis) and Alnilam (Epsilon Orionis), the three stars make up the belt of Orion, known by many names among ancient cultures. When Orion is close to the meridian, Mintaka is the right-most of the belt's stars as seen by an observer in the Northern Hemisphere facing south. Mintaka is actually a multiple star at the western end of Orion's belt, with a magnitude 7 star about 52" away from the main component and an even fainter star in between. The main component itself is also double, consisting of a class B giant and a smaller but hotter class O. The stars orbit each other every 5.73 days. These two stars are both about 90,000 times as luminous as the Sun with a mass of some 20 solar masses. In 1904, Johannes Hartmann discovered that interstellar space contains a thin gas, the interstellar medium, by using Mintaka as a background source. Mintaka was also seen by astrologers as a portent of good fortune. The three belt stars were collectively known by many names in many cultures.
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    2 votes
    118
    Omicron Cassiopeiae

    Omicron Cassiopeiae

    • Category: Star
    Omicron Cassiopeiae (ο Cas, ο Cassiopeiae) is a triple star system in the constellation Cassiopeia. It is approximately 910 light years from Earth. The primary component, ο Cassiopeiae A, is a blue-white B-type giant with a mean apparent magnitude of +4.54. It is classified as a Gamma Cassiopeiae type variable star and its brightness varies from magnitude +4.50 to +4.62. The primary is a spectroscopic binary, and its close companion completes one orbit every 2.83 years. A more distant companion, ο Cassiopeiae B, lies 33.6 arcseconds away. It is an eleventh magnitude, yellow-white F-type main sequence dwarf.
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    2 votes
    119
    Phobos

    Phobos

    • Category: Natural satellite
    Phobos ( /ˈfoʊbəs/ FOH-bəs; Greek: Φόβος; systematic designation: Mars I) is the larger and closer of the two natural satellites of Mars. With a mean radius of 11.1 km (6.9 mi), Phobos is 7.24 times as massive as the second moon Deimos. It is named after the Greek god Phobos (which means "fear"), a son of Ares (Mars). Both moons were discovered in 1877. A small, irregularly shaped object, Phobos orbits about 9,400 km (5,800 mi) from the center of Mars, or about 6,000 km (3,700 mi) from the Martian surface, closer to its primary than any other known planetary moon. Phobos is one of the least reflective bodies in the Solar System, and features a large impact crater, Stickney crater. It orbits so close to the planet that it moves around Mars faster than Mars rotates. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 h 15 min or less, and set in the east twice in each Martian day. Due to its short orbital period and tidal interactions, Phobos's orbital radius is decreasing and it will eventually either impact the surface of Mars or break up into a planetary ring. Phobos was discovered by astronomer Asaph Hall on August 18, 1877, at the
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    2 votes
    120
    Arcturus

    Arcturus

    • Category: Star
    Arcturus ( /ɑrkˈtjʊərəs/; α Boo, α Boötis, Alpha Boötis) is the brightest star in the constellation Boötes and the northern celestial hemisphere. With a visual magnitude of −0.04, it is the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. It is a relatively close star at only 36.7 light-years from Earth, and, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood. A type K1.5 IIIpe orange giant star, with an absolute magnitude of -0.30. It has likely exhausted its hydrogen and has begun fusing helium into oxygen and carbon in its core. It will continue to expand before sloughing off its outer shell and ending its life as a white dwarf inside a planetary nebula. As one of the brightest stars in the sky, Arcturus has been significant to observers since antiquity. In Mesopotamia, it was linked to the god Enlil, and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. Ptolemy described Arcturus as subrufa "slightly red", and it has a B-V color index of +1.23, roughly midway
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    1 votes
    121
    Beta Aquilae

    Beta Aquilae

    • Category: Star
    Beta Aquilae (β Aql, β Aquilae) is a star in the constellation Aquila. It has the traditional name Alshain from the Perso-Arabic term الشاهين aš-šāhīn "the (peregrine) falcon", perhaps by folk etymology from the Persian šāhīn tarāzū (or possibly šāhīn tara zed; see γ Aquilae), the Persian name for the asterism α, β and γ Aquilae. In Chinese, 河鼓 (Hé Gŭ), meaning River Drum, refers to an asterism consisting of β Aquilae, Altair and γ Aql. Consequently, β Aquilae itself is known as 河鼓一 (Hé Gŭ yī, English: the First Star of River Drum.) In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Unuk al Ghyrab (عنق ألغراب - únuq al-ghuraab), which was translated into Latin as Collum Corvi, meaning the crow's neck. Beta Aquilae has magnitude 3.71 and is of spectral class G8IV. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is approximately 44.7 light years from Earth. It has a 12th magnitude optical companion, β Aquilae B, which is 13 arcseconds away in the sky. In Chinese mythology, The Princess and the Cowherd, this star and γ Aql, are children of Niulang (牛郎, The Cowherd,
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    1 votes
    122
    Beta Pegasi

    Beta Pegasi

    • Category: Star
    Beta Pegasi (β Peg, β Pegasi) is a star in the constellation Pegasus. The apparent visual magnitude of this star averages 2.42, making it the second brightest star in the constellation after Epsilon Pegasi. Its traditional name is Scheat, a name that has also been used for Delta Aquarii. According to Richard H. Allen, this name comes from the Arabic Al Sā'id for 'the upper arm', or from Sa'd. Arabian astronomers named it Mankib al Faras, meaning the "Horse's shoulder". It forms the upper right corner of the Great Square of Pegasus, a prominent rectangular asterism. Based upon parallax measurements, Beta Pegasi is located about 196 light-years (60 parsecs) from the Earth. It is unusual among bright stars in having a relatively cool surface temperature compared to stars like the Sun. This star has a stellar classification of M2.3 II-III, which indicates the spectrum has the characteristics of a star part way between a subgiant and a red giant. It has expanded until it is some 95 times as large, and has a total luminosity of 1500 times that of the Sun. The effective temperature of the star's outer envelope is about 3,700 K, giving the star the characteristic orange-red hue of an
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    1 votes
    123
    Beta Ursae Majoris

    Beta Ursae Majoris

    • Category: Star
    Beta Ursae Majoris (Beta UMa, β Ursae Majoris, β UMa) is a star in the northern circumpolar constellation of Ursa Major. It has the traditional name Merak. The apparent visual magnitude of this star is +2.37, which means it is readily visible to the naked eye. It is more familiar to northern hemisphere observers as one of the "pointer stars" in the Big Dipper, or "The Plough" in England, which is a prominent asterism of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby Alpha Ursae Majoris (Dubhe) extends to Polaris, the north star. Based upon parallax measurements of this star, it is located at a distance of 79.7 light-years (24.4 parsecs) from the Earth. The spectrum shows this to have a stellar classification of A1 V, making it a fairly typical main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The effective temperature of the outer envelope is about 9,225 K, giving it a white-hued glow that is typical for A-type stars. It is larger than the Sun, with about 2.7 times the mass and 2.84 times the Solar radius. If they were viewed from the same distance,
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    1 votes
    124
    Delta Aquilae

    Delta Aquilae

    • Category: Star
    Delta Aquilae (δ Aql, δ Aquilae) is a binary star system in the equatorial constellation of Aquila. The traditional name for this star is Denebokab. It has an apparent visual magnitude of 3.4 and, based upon parallax measurements, is located about 50.6 light-years (15.5 parsecs) from Earth. Delta Aquilae is an astrometric binary where the two components orbit each other with a period of 3.422 years and an eccentricity of about 0.36. This is a type of binary star system where the presence of the secondary component is revealed by its gravitational perturbation of the primary. The individual components have not been resolved with a telescope. The primary component, Delta Aquilae A, is a subgiant star with a stellar classification of F0 IV, where the luminosity class of IV indicates it is in the process of exhausting the supply of hydrogen at its core and evolving into a giant star. The mass of the star is 65% greater than the Sun and it has expanded to more than double the Sun's radius. It is radiating around 7–8 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 7,016 K, giving it the yellow-white hue of an F-type star. Delta Aquilae A is a
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    1 votes
    125
    Epsilon Aurigae

    Epsilon Aurigae

    • Category: Star
    Epsilon Aurigae (ε Aur, ε Aurigae) is the Bayer designation for a star in the northern constellation of Auriga. It is traditionally known as Almaaz, Haldus, or Al Anz. Epsilon Aurigae is an unusual eclipsing binary system comprising an F0 supergiant and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars. About every 27 years, Epsilon Aurigae's brightness drops from an apparent visual magnitude of +2.92 to +3.83. This dimming lasts 640–730 days. In addition to this eclipse, the system also has a low amplitude pulsation with a non-consistent period of around 66 days. The distance to the system is still a subject of debate, but modern estimates place it approximately 2,000 light years from Earth. Epsilon Aurigae was first suspected to be a variable star when German astronomer Johann Fritsch observed it in 1821. Later observations by Eduard Heis and Friedrich Wilhelm Argelander reinforced Fritsch's initial suspicions and attracted attention to the star. Hans Ludendorff, however, was the first to study it in great detail. His work revealed that the system was an eclipsing binary variable, a star
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    1 votes
    126
    Omicron Leonis

    Omicron Leonis

    • Category: Star
    Omicron Leonis (ο Leo, ο Leonis) is a binary star in the constellation Leo. It has the traditional name Subra. The two stars of Subra are of spectral class F9III (a giant star) for the primary and A5mV (a main sequence star) for the secondary. Their combined apparent magnitude is +3.53.
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    127
    Pollux

    Pollux

    • Category: Star
    Pollux (β Gem, β Geminorum, Beta Geminorum) is a star in the northern constellation of Gemini, the Twins. It is an evolved giant star with an orange hue. At an apparent visual magnitude of 1.1, Pollux is the brightest star in the constellation; brighter even than its neighbor Castor (Alpha Geminorum). Parallax measurements made with the Hipparcos astrometry satellite place it at a distance of about 33.78 light-years (10.36 parsecs) from Earth. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. In 2006, Pollux was confirmed to have an extrasolar planet orbiting it. This star is larger than the Sun, with about two times its mass and almost nine times its radius. Once an A-type main sequence star, Pollux has exhausted the hydrogen at its core and evolved into a giant star with a stellar classification of K0 III. The effective temperature of this star's outer envelope is about 4,666 K, which lies in the range that produces the characteristic orange hue of K-type stars. Pollux appears to be rotating at a leisurely rate, with a protected rotational velocity of 2.8 km s. The abundance of elements other than hydrogen and
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    1 votes
    128
    PSR B1257+12

    PSR B1257+12

    • Category: Star
    PSR B1257+12, sometimes abbreviated as PSR 1257+12, is a pulsar located 1000 light years from the Sun. In 2007, it was confirmed that three extrasolar planets orbit the pulsar. PSR B1257+12 is in the constellation of Virgo. The designation PSR B1257+12 refers to its coordinates in the B1950.0 epoch. PSR B1257+12 was discovered by the Polish astronomer Aleksander Wolszczan in 1990 using the Arecibo radio telescope. It is a millisecond pulsar, a kind of neutron star, and was found to have anomalies in the pulsation period, which led to investigations as to the cause of the irregular pulses. In 1992 Wolszczan and Dale Frail published a famous paper on the first confirmed discovery of planets outside our solar system. Using refined methods one more planet was found orbiting this pulsar in 1994, and a fourth was found in 2002. The discovery started a search for planets orbiting other pulsars, but it turned out such are rare, only one other planet have been confirmed orbiting PSR B1620-26. PSR B1257+12 has a rotation period of 6.22 milliseconds (9,650 rpm). In 1992, Aleksander Wolszczan and Dale Frail discovered that the pulsar has two planets. These were the first extrasolar planets
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    129
    Titan

    Titan

    • Category: Natural satellite
    • Locations: Adiri
    Titan (or Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter roughly 50% larger than Earth's moon and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter's moon Ganymede, and it is larger by volume than the smallest planet, Mercury, although only half as massive. Titan was the first known moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens, and was the fifth moon of a planet apart from the Earth to be discovered. Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in the satellite's polar regions. The surface is geologically young; although mountains and several possible
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    130
    Eta Carinae

    Eta Carinae

    • Category: Star
    Eta Carinae (η Carinae or η Car) is a stellar system in the constellation Carina, about 7,500 to 8,000 light-years from the Sun. The system contains at least two stars, one of which is a Luminous Blue Variable (LBV), which during the early stages of its life had a mass of around 150 solar masses, of which it has lost at least 30 since. It is thought that a hot supergiant of approximately 30 solar masses exists in orbit around its larger companion star, although an enormous thick red nebula surrounding Eta Carinae makes it impossible to see optically. Eta Carinae is enclosed in the Homunculus Nebula, itself part of the much larger Carina Nebula. Its combined luminosity is about five million times that of the Sun and has an estimated system mass in excess of 100 solar masses. It is not visible north of latitude 30°N and is circumpolar south of latitude 30°S. Because of its mass and the stage of life, it is expected to explode in a supernova or even hypernova in the astronomically near future. In traditional Chinese astronomy, Eta Carinae has the names Tseen She (from the Chinese 天社 [Mandarin: tiānshè] "Heaven's altar") and Foramen. It is also known as 海山二 (Hǎi Shān èr, English: the
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    3 votes
    131
    Upsilon1 Cassiopeiae

    Upsilon1 Cassiopeiae

    • Category: Star
    Upsilon Cassiopeiae (υ Cas, υ Cassiopeiae) is a triple star system in the constellation Cassiopeia. υ Cassiopeiae is an orange K-type giant with an apparent magnitude of +4.83. It is approximately 407 light years from Earth.
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    132
    Spica

    Spica

    • Category: Star
    Spica (α Vir, α Virginis, Alpha Virginis, pronounced /ˈspaɪkə/) is the brightest star in the constellation Virgo, and the 15th brightest star in the nighttime sky. It is 260 light years distant from Earth. A blue giant, it is a variable of the Beta Cephei type. Spica is believed to be the star that provided Hipparchus with the data which enabled him to discover precession of the equinoxes. A temple to Menat (an early Hathor) at Thebes was oriented with reference to Spica when it was constructed in 3200 BC and, over time, precession resulted in a slow but noticeable change in the location of Spica relative to the temple. Nicolaus Copernicus made many observations of Spica with his home-made triquetrum for his researches on precession. As one of the nearest massive binary star systems to the Sun, Spica has been the subject of many observational studies. Spica is a close binary star whose components orbit about each other every four days. They remain sufficiently close together that they can not be resolved as individual stars through a telescope. The changes in the orbital motion of this pair results in a Doppler shift in the absorption lines of their respective spectra, making them
    5.75
    4 votes
    133
    Alpha Cephei

    Alpha Cephei

    • Category: Star
    Alpha Cephei (α Cep, α Cephei) is a second magnitude star in the constellation of Cepheus that is relatively close to Earth at only 49 light years. It has the traditional name Alderamin, an Arabic name meaning "the right arm". With a declination in excess of 62 degrees north, Alderamin is mostly visible to observers in the northern hemisphere, though the star is still visible as far south as ± 27° South latitude, albeit just above the horizon. The star is circumpolar throughout all of Europe, northern Asia, Canada and American cities as far south as San Diego on the west coast but not quite as far as Miami on the east coast. All other locations around the globe having a latitude greater than ± 27° North will notice that the star is always visible in the night sky. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in light polluted cities. Alderamin is a white Class A star, evolving off of the main sequence into a subgiant, probably on its way to becoming a red giant as its hydrogen supply runs low. In 2007, the star's apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a
    7.50
    2 votes
    134
    Alpha Comae Berenices

    Alpha Comae Berenices

    • Category: Star
    Alpha Comae Berenices (Alpha Com, α Com, α Comae Berenices) is a star in the constellation Coma Berenices (Berenice's Hair). Although it has the Bayer designation "alpha", at magnitude 4.32 it is actually fainter than Beta Comae Berenices. It has the traditional name Diadem. It is said to represent the crown worn by Queen Berenice. A name occasionally seen is Al Dafirah, from the Arabic الضفيرة ađ̧-đ̧afīrah "the braid". In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of α Comae Berenices, η Virginis, γ Virginis, δ Virginis and ε Virginis. Consequently, α Comae Berenices itself is known as 太微左垣五 (Tài Wēi Zuǒ Yuán wǔ, English: the Fifth Star of Left Wall of Supreme Palace Enclosure.), representing 東上將 (Dōngshǎngjiāng), meaning The First Eastern General. 東上將 (Dōngshǎngjiāng), westernized into Shang Tseang, but the name Shang Tseang was designated for "v Comae Berenices" by R.H. Allen and the meaning is "a Higher General" It is a binary star, with almost equal components of magnitudes 5.05m and 5.08m orbiting each other with a period of 25.87 years. The system, estimated to be 65 light years distant, appears so
    7.50
    2 votes
    135
    Beta Tauri

    Beta Tauri

    • Category: Star
    Beta Tauri (β Tau, β Tauri) is the second brightest star in the constellation Taurus, with an apparent magnitude of 1.68. Because it is on the boundary of Taurus and Auriga, it also has the redundant Bayer designation Gamma Aurigae (γ Aur), which today is rarely used. The star has the traditional name Elnath—a reference to "the butting" of the bull's horns. Elnath's absolute magnitude is -1.34, similar to another Taurean star, Maia in the Pleiadian star cluster. Like Maia, Elnath is a B class giant with a luminosity 700 times solar. However being approximately 130 light years distant compared to Maia's estimated 360 light years, Elnath ranks as the second brightest star in the constellation. Uniquely positioned along the plane of our Milky Way Galaxy a few degrees west of the galactic anticenter, Elnath heralds a rich collection of nebulae and star clusters. Relative to our Sun, β Tauri is notable for a high abundance of manganese, but little calcium and magnesium. This star has begun to evolve away from the main sequence. This star can be occulted by the moon. Such occultations occur when the moon's ascending node is near the vernal equinox, as is the case in 2007. Most
    7.50
    2 votes
    136
    Delta Canis Majoris

    Delta Canis Majoris

    • Category: Star
    Delta Canis Majoris (δ CMa, δ Canis Majoris) is a star in the constellation Canis Major. It has the traditional name Wezen or Wesen. It is a yellow-white F-type supergiant with an apparent magnitude of +1.83. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. δ Canis Majoris is the third brightest star in the constellation after Sirius and Adhara, with an apparent magnitude of +1.83, and is a white or yellow-white in colour. Lying about 10 degrees south southeast of Sirius, it only rises to about 11 degrees above the horizon at the latitude of the United Kingdom. The open cluster NGC 2354 is located only 1.3 degrees east of Delta Canis Majoris. As with the rest of Canis Major, Wezen is most visible in winter skies in the northern hemisphere, and summer skies in the southern. It theoretically makes up the Great Dog's hind quarter. The traditional name, Wezen, is derived from the medieval Arabic وزن al-wazn, which means "weight" in modern Arabic. The name was for one of a pair of stars, the other being Hadar, which has now come to refer to Beta Centauri. It is unclear whether the pair of stars was originally Alpha
    7.50
    2 votes
    137
    Delta Scuti

    Delta Scuti

    • Category: Star
    Delta Scuti (δ Sct, δ Scuti) is a giant star in the southern constellation Scutum. With an apparent visual magnitude of 4.72, it is the fifth brightest star in this small and otherwise undistinguished constellation. Analysis of the parallax measurements made during the Hipparcos mission place this star at a distance of about 202 light-years (62 parsecs) from Earth. Delta Scuti is the prototype of the Delta Scuti type variable stars. It is a high-amplitude δ Scuti type pulsator with light variations of about 0.15 minutes. The peculiar chemical abundances of this star are similar to those of Am stars. In 1900, William W. Campbell and William H. Wright used the Mills spectrograph at the Lick Observatory to determine that this star has a variable radial velocity. The 0.19377 day period of this variability as well as 0.2 magnitude changes in luminosity demonstrated in 1935 that the variability was intrinsic, rather than being the result of a spectroscopic binary. In 1938, a secondary period was discovered and a pulsation theory was proposed to model the variation. Since then, observation of Delta Scuti has shown that it pulsates in multiple discrete radial and non-radial modes. The
    7.50
    2 votes
    138
    Gamma Cephei

    Gamma Cephei

    • Category: Star
    Gamma Cephei (γ Cep, γ Cephei), traditionally named Errai, Er Rai, and or Alrai, is a binary star system approximately 45 light-years away in the constellation of Cepheus. Gamma Cephei contains an apparent magnitude of 3.22. The visible part of the system is a stellar class K1III-IV orange subgiant star on its first ascent off the main sequence. It is about 6.6 billion years old (based on Fe/H metallicity). Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth's northern pole star, due to the precession of the equinoxes. It will be closer to the northern celestial pole than Polaris around 3000 CE and will make its closest approach around 4000 CE. The "title" will pass to ι Cephei some time around 5200 CE. The star has a companion star with a mass approximately 0.409 times that of our Sun. Gamma Cephei B is of stellar mass and is assumed to be of similar age to its primary. It is probably a red dwarf of class M4, 6.2 degrees of magnitude fainter than the K-type primary star. Gamma Cephei's traditional name derives from the Arabic الراعي
    7.50
    2 votes
    139
    Gamma Cygni

    Gamma Cygni

    • Category: Star
    Gamma Cygni (γ Cyg, γ Cygni) is the Bayer designation for a star in the northern constellation Cygnus, forming the intersection of an asterism of five stars called the Northern Cross. It has the traditional name Sadr (also spelled Sadir or Sador), which name comes from the Arabic word صدر şadr, "chest", the same word which gave rise to the star Schedar (Alpha Cassiopeiae). In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Sadr al Dedjadjet, (صدرألدجاجة-şadr aldajaaja), which was translated into Latin as Pectus Gallinǣ, meaning the hen's chest. In Chinese, 天津 (Tiān Jīn), meaning Celestial Ford, refers to an asterism consisting of γ Cygni, δ Cygni, 30 Cygni, α Cygni, ν Cygni, τ Cygni, υ Cygni, ζ Cygni and ε Cygni. Consequently, γ Cygni itself is known as 天津一 (Tiān Jīn yī, English: the First Star of Celestial Ford.). With an apparent visual magnitude of 2.23, this is among the brighter stars visible in the night sky. Parallax measurements give a distance estimate of 1,800 light years (560 parsecs), with a 15% margin of error. The stellar classification of this star is F8 Iab, indicating that it has reached the supergiant stage of its
    7.50
    2 votes
    140
    Mira

    Mira

    • Category: Star
    Mira ( /ˈmaɪrə/ or  /ˈmɪrə/) also known as Omicron Ceti (ο Ceti, ο Cet), is a red giant star estimated 200-400 light years away in the constellation Cetus. Mira is a binary star, consisting of the red giant Mira A along with Mira B. Mira A is also an oscillating variable star and was the first non-supernova variable star discovered, with the possible exception of Algol. Apart from the unusual Eta Carinae, Mira is the brightest periodic variable in the sky that is not visible to the naked eye for part of its cycle. Its distance is uncertain; pre-Hipparcos estimates centered around 220 light-years, while Hipparcos data suggest a distance of 418 light-years, albeit with a margin of error of ~14%. Evidence that the variability of Mira was known in ancient China, Babylon or Greece is at best only circumstantial. What is certain is that the variability of Mira was recorded by the astronomer David Fabricius beginning on August 3, 1596. Observing what he thought was the planet Mercury (later identified as Jupiter), he needed a reference star for comparing positions and picked a previously unremarked third-magnitude star nearby. By August 21, however, it had increased in brightness by one
    7.50
    2 votes
    141
    Phi Andromedae

    Phi Andromedae

    • Category: Star
    Phi Andromedae (φ Andromedae, φ And) is the Bayer designation for a binary star system near the border of the northern constellation of Andromeda. This system has a combined apparent visual magnitude of 4.25 and is visible to the naked eye. Based upon parallax measurements made during the Hipparcos mission, this star system is located at a distance of about 720 light-years (220 parsecs) from Earth. With χ And it forms the Chinese asterism 軍南門 (Keun Nan Mun, Mandarin jūnnánmén), "the South Gate of the Camp". The 4.46 magnitude primary component is a Be star with a stellar classification of B7 Ve, indicating that it is a B-type main sequence star that shows prominent emission lines of hydrogen in its spectrum. These emission lines come from a flattened disk of hot, decreated gas that is orbiting the host star. The star is rotating rapidly with a projected rotational velocity of 75 km/s. The pole of the star is inclined around 20° to the line of sight from the Earth. The 6.06 magnitude companion star is a B-type main sequence star with a classification of B9 V. On average the two stars are separated by about 0.6 arcseconds and have an orbital period of roughly 554 years. Based upon
    7.50
    2 votes
    142
    Pi3 Orionis

    Pi3 Orionis

    • Category: Star
    Pi Orionis (π Ori, π Orionis) is the Bayer designation for a star in the equatorial constellation of Orion. It has the traditional name of Tabit and the Flamsteed designation 1 Orionis. At an apparent visual magnitude of 3.16, it is readily visible to the naked eye. Pi Orionis is the brightest star in the lion's hide (or shield) that Orion is holding. The distance to this star, as measured using the parallax technique, is 26.32 light-years (8.07 parsecs). Though no extrasolar planets have been observed around Pi Orionis, the star is considered a prime location for planets as small as the Earth. Pi Orionis is a main-sequence star of spectral type F6 V. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Compared to the Sun, it has about 124% of the mass, 132% of the radius, and nearly 3 times the luminosity. This energy is being radiated from the star's outer atmosphere at an effective temperature of 6,516 K, giving it the yellow-white glow of an F-type star. Pi Orionis is most likely single; a nearby star is probably an optical companion. Although a periodicity of 73.26 days has been observed in the star's radial
    7.50
    2 votes
    143
    Neptune

    Neptune

    • Category: Planet
    • Locations: The Great Dark Spot
    Neptune is the eighth and farthest planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Neptune is 17 times the mass of Earth and is somewhat more massive than its near-twin Uranus, which is 15 times the mass of Earth but not as dense. On average, Neptune orbits the Sun at a distance of 30.1 AU, approximately 30 times the Earth–Sun distance. Named for the Roman god of the sea, its astronomical symbol is ♆, a stylised version of the god Neptune's trident. Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 12 moons were located telescopically until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on 25 August 1989. Neptune is similar in
    5.50
    4 votes
    144
    Xi Ursae Majoris

    Xi Ursae Majoris

    • Category: Star
    Xi Ursae Majoris (Xi UMa, ξ Ursae Majoris, ξ UMa) is a star system in the constellation Ursa Major. On May 2, 1780, Sir William Herschel discovered that this was a binary star system, making it the first such system ever discovered. It was the first visual double star for which an orbit was calculated, when it was computed by Félix Savary in 1828. The two components are yellow G-type main-sequence stars. The brighter component, Xi Ursae Majoris A, has a mean apparent magnitude of +4.41. It is classified as an RS Canum Venaticorum type variable star and its brightness varies by 0.01 magnitudes. The companion star, Xi Ursae Majoris B has an apparent magnitude of +4.87. The orbital period of the two stars is 59.84 years, and they are currently separated by 1.2 arcseconds, or at least 10 AUs. Each component of this double star is itself a spectroscopic binary. B's binary companion, denoted Xi Ursae Majoris Bb, is unresolved, but the binary star is known to have an orbital period of 3.98 days. The masses of both A and B's companions (Ab and Bb) (deduced by the sum total mass of the system minus the likely masses of Aa and Ba determined by their class) indicate that they are probably MV
    5.50
    4 votes
    145
    40 Eridani

    40 Eridani

    • Category: Star
    40 Eridani (also known as Omicron Eridani, or Keid, from the Arabic word qayd, (egg) shells) is a triple star system less than 16.5 light years away from Earth. It is in the constellation Eridanus. The primary star of the system, 40 Eridani A, is easily visible to the naked eye. The pair 40 Eridani B/C was discovered on January 31, 1783, by William Herschel. It was again observed by Friedrich Georg Wilhelm Struve in 1825 and by Otto Wilhelm von Struve in 1851. In 1910, it was discovered that although component B was a faint star, it was white in color. This meant that it had to be a small star; in fact it was a white dwarf, the first discovered. 40 Eridani A is a main-sequence dwarf of spectral type K1. Its two companion stars, 40 Eridani B and 40 Eridani C, are a 9th magnitude white dwarf (spectral type DA4) and an 11th magnitude red dwarf flare star (spectral type M4.5e) which has the variable star designation DY Eridani. Presumably, while B was a main-sequence star, it was the most massive member of the system, but ejected most of its mass before it became a white dwarf. B and C orbit each other approximately 400 astronomical units from the primary star, A. Their orbit has a
    6.33
    3 votes
    146
    Epsilon Cassiopeiae

    Epsilon Cassiopeiae

    • Category: Star
    Epsilon Cassiopeiae (ε Cas, ε Cassiopeiae) is a star system in the constellation Cassiopeia. It has the traditional name Segin. With an apparent visual magnitude of 3.4, this is one of the brightest stars in the constellation. The distance to this star has been determined directly using parallax measurements, yielding a value of around 390–430 light-years (120–130 parsecs). This is a giant star with a stellar classification of B3 III, indicating that is has exhausted the hydrogen at its core and entered a later evolutionary stages of its lifetime. Cote et al. (2003) indicate that it displays the spectral properties of a Be star, even though it is not categorized as such. The presence of emission lines in the spectrum indicates the presence of a circumstellar shell of gas that has been thrown off by the star. The outer atmosphere of Epsilon Cassiopeiae has an effective temperature of 15,174 K, giving it the blue-white hue of a B-type star. The interferometer-measured angular diameter is 0.43 milliarcseconds. At the estimated distance of this star, this yields a physical size of roughly 6 times the radius of the Sun. Observation of this star during the Hipparcos mission suggest that
    6.33
    3 votes
    147
    Gliese 570

    Gliese 570

    • Category: Star
    Gliese 570, also known as 33 G. Librae, is a ternary star system approximately 19 light-years away. The primary star is an orange dwarf star (much dimmer and smaller than the Sun). The other secondary stars are themselves a binary system, two red dwarfs that orbit one another. A brown dwarf has been confirmed to be orbiting in the system. As of 1998, an extrasolar planet was thought to orbit the primary star, but it was discounted in 2000. In the night sky, the Gliese 570 system lies in the southwestern part of Libra. The system is southwest of Alpha Librae and northwest of Sigma Librae. In the early 1990s, the European Hipparcos mission measured the parallax of components B and C, suggesting that the system was at a distance of 24.4 light-years from the Sun. This, however, was a relatively large error as Earth-based parallax and orbit observations suggest that the two stars are actually part of a system with Gliese 570 A, and must actually lie at the same distance. The primary star of the system (component A) is an orange dwarf star that may just have over three fourths the mass of the Sun, about 77 percent of its radius, and only 15.6 percent of its visual luminosity. It has a
    6.33
    3 votes
    148
    Phi Cassiopeiae

    Phi Cassiopeiae

    • Category: Star
    Phi Cassiopeiae (φ Cas, φ Cassiopeiae) is a star in the constellation Cassiopeia. φ Cassiopeiae is a yellow-white F-type supergiant with an apparent magnitude of +4.95. It is approximately 2300 light years from Earth. It appears among the stars of the open cluster NGC 457, but it is a foreground star and not a member of the cluster.
    6.33
    3 votes
    149
    Theta Eridani

    Theta Eridani

    • Category: Star
    Theta Eridani (θ Eri, θ Eridani) is a star in the constellation Eridanus. It has the traditional name Acamar from the Arabic آخِر النَّهْر  Ākhir an-nahr which means "the end of the river". Historically, Acamar represented the end of the constellation Eridanus. Now that distinction is held by the star Achernar, a star which shares the same Arabic etymology. Achernar is not visible from the Greek isles (latitudes > 33° North), hence the choice of Acamar as the river's end during the time of Hipparchus and later Ptolemy. The term Ākhir an-nahr or Achr al Nahr was appeared in the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, which was translated into Latin as Postrema Fluminis. In Chinese, 天園 (Tiān Yuán), meaning Celestial Orchard, refers to an asterism consisting of θ Eridani, χ Eridani, φ Eridani, κ Eridani, HD 16754, HD 23319, HD 24072, HD 24160, υ Eridani, 43 Eridani, υ Eridani and υ Eridani. Consequently, θ Eridani itself is known as 天園六 (Tiān Yuán liù, English: the Sixth Star of Celestial Orchard.) Acamar is a double star with some evidence suggesting it is part of a multiple star system. The main star, θ Eri, is of the spectral class A4 and has a +3.2
    6.33
    3 votes
    150
    Theta1 C orionis

    Theta1 C orionis

    • Category: Star
    Theta Orionis C is a member of the Trapezium open cluster that lies within the Orion Nebula. The star C is the most massive of the four bright stars at the heart of the cluster. It is an O class blue main sequence star and has the highest surface temperature of any star visible to the naked eye; it is one of the most luminous stars known, with an estimated absolute magnitude in visible wavelengths of about −3.2. Its high luminosity and large distance (about 1,500 light years) give it an apparent visible magnitude of 5.1. This star is responsible for generating most of the ultraviolet light that is slowly ionizing (and perhaps photoevaporating) the Orion Nebula. This UV light is also the primary cause of the glow that illuminates the Orion Nebula. The star emits a powerful stellar wind that is a hundred thousand times stronger than the Sun's, and the outpouring gas moves at 1,000 km/s. Infrared observations of Theta Orionis C have shown that it is actually a close binary system. It also displays optical variability and is a variable X-ray source. It is expected that this star will expand into a red supergiant and end its life as a supernova within a few million years from now.
    6.33
    3 votes
    151
    61 Virginis

    61 Virginis

    • Category: Star
    61 Virginis (abbreviated 61 Vir) is a G5V class star slightly less massive than the Sun (G2V), located about 27.8 light-years away in the constellation of Virgo. The composition of this star is nearly identical to the Sun and there is only a low level of activity in the stellar chromosphere. This star is rotating once every 29 days at the equator. The space velocity components of this star are U = –37.9, V = –35.3 and W = –24.7 km/s. 61 Vir is orbiting through the Milky Way galaxy at a distance of 6.9 kpc from the core, with an eccentricity of 0.15. It is believed to be a disk star with an estimated age of more than six billion years. 61 Virginis (G5V) is the first well established main sequence yellow dwarf star very similar to the Sun with a potential Super-Earth, though COROT-7 (a borderline orange dwarf) is arguably the first. There was some evidence that it may have a jovian planet, but it seemed not to have a nearby massive companion. A subsequent study also failed to find the large substellar companion (with 20 to 80 times the mass of Jupiter) or a Jupiter-class planet, so it was a good candidate for possessing a family of terrestrial planets, with an orbit slightly smaller
    8.00
    1 votes
    152
    Alcyone

    Alcyone

    • Category: Star
    Alcyone (η Tau, η Tauri, Eta Tauri) is a star system in the constellation Taurus. It is the brightest star in the Pleiades open cluster, which is a young cluster, aged at less than 50 million years. Alcyone is approximately 370 light years from Earth. It is named after the mythological figure Alcyone, one of the mythological Pleiades. It is known as 昴宿六 (the Sixth Star of the Hairy Head) in Chinese. The main star, known as Alcyone A, is a blue-white B-type giant similar to many of the other B-type stars in the Pleiades cluster. It has an apparent magnitude of +2.87 (absolute magnitude = −2.39), and a radius almost 10 times that of the Sun. Its temperature is approximately 13,000 K giving it a total luminosity that is 2,400 times solar. The spectral type of B7IIIe indicates that emission lines are present in its spectrum. Like many Be stars, Alcyone A has a high rotational velocity of 215 km/s, which has created a gaseous disk flung into orbit around the star from its equator. Alcyone is an eclipsing binary, and the two components have a separation of 0.031 arcseconds, or about the distance from the Sun to Jupiter. The binary star is orbited by three companions. Alcyone B and
    8.00
    1 votes
    153
    Beta Cancri

    Beta Cancri

    • Category: Star
    Beta Cancri (β Cnc, β Cancri) is the brightest star in the constellation Cancer. It has the traditional name Tarf or Al Tarf (Altarf), certainly a derivation from Arabic الطرف aṭ-ṭarf "the eye" or طرفة aṭ-ṭarfah "the glance (of Leo)". It is approximately 290 light years from Earth. This is an orange K-type giant,about 49 times the radius of the Sun, with an apparent magnitude of +3.50 and absolute magnitude of -1.25 (visual). It has a faint, fourteenth magnitude, red dwarf companion star located 29 arcseconds away. Jim Kaler's Stars: Al Tarf
    8.00
    1 votes
    154
    Cygnus X-1

    Cygnus X-1

    • Category: Astrophysical X-ray source
    Cygnus X-1 (abbreviated Cyg X-1) is a well-known galactic X-ray source in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 2.3×10 WmHz (2.3×10 Jansky). Cygnus X-1 was the first X-ray source widely accepted to be a black hole candidate and it remains among the most studied astronomical objects in its class. It is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too compact to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon is probably about 26 km. Cygnus X-1 belongs to a high-mass X-ray binary system about 6,100 ly from the Sun that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets, arranged perpendicular to the disk, are carrying part of the infalling material
    8.00
    1 votes
    155
    Delta Leonis

    Delta Leonis

    • Category: Star
    Delta Leonis (δ Leo, δ Leonis) is a star in the zodiac constellation of Leo. It has the traditional names Zosma (or Zozma) and Duhr. Rare spellings include Zozca, Zosca, Zubra, and Dhur. The name Zosma means girdle in ancient Greek, referring to the star's location in its constellation, on the hip of the lion. Based upon parallax measurements, it lies at a distance of about 58.4 light-years (17.9 parsecs) from the Earth. Zosma is a relatively ordinary main sequence star with a stellar classification of A4 V, making it is somewhat larger and hotter than the Sun. It is a fairly well-studied star, allowing relatively accurate measurements of its age and size. The radius of the star, as measured directly using an interferometer, is about 214% of the Sun's radius and it is emitting more than 15 times as much luminosity as the Sun. The energy is being emitted from the outer envelope with an effective temperature 8,296 K, giving it the white hue characteristic of an A-type star. Having a larger mass than the Sun it will have a shorter lifespan, and in another 600 million years or so will swell into an orange or red giant star before decaying quietly into a white dwarf. This star is
    8.00
    1 votes
    156
    Epsilon Eridani

    Epsilon Eridani

    • Category: Star
    Epsilon Eridani (ε Eri, ε Eridani) is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years (ly), it has an apparent magnitude of 3.73. It is the third closest of the individual stars or star systems visible to the unaided eye and was the closest star known to host a planet until the discovery of Alpha Centauri Bb. Its age is estimated at less than a billion years. Because of its youth, Epsilon Eridani has a higher level of magnetic activity than the present-day Sun, with a stellar wind 30 times as strong. Its rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a comparatively lower level of elements heavier than helium. Astronomers categorize it as a main-sequence star of spectral class K2, which means that energy generated at the core through nuclear fusion of hydrogen is emitted from the surface at a temperature of about 5,000 K, giving the star an orange hue. The motion of this star along the line of sight to the Earth, known as the radial velocity, has been regularly
    8.00
    1 votes
    157
    HD 128311

    HD 128311

    • Category: Star
    HD 128311 or HN Boötis is an orange main-sequence star located approximately 54 light-years away in the constellation of Boötes. Two extrasolar planet candidates have been detected in orbit around this star. In 2002, the discovery of the planet HD 128311 b was announced by Paul Butler. In 2005, the discovery of a second planet HD 128311 c was announced by Steve Vogt. Most likely, the system has been formed in a very turbulent disc. The authors were able to show with both analytic and numerical models that certain libration modes are readily excited by turbulence. It was initially thought that the system could have been resulted from planet planet scattering, but this is rather unlikely.
    8.00
    1 votes
    158
    HD 69830

    HD 69830

    • Category: Star
    HD 69830 (285 G. Puppis) is an orange dwarf star approximately 41 light-years away in the constellation of Puppis. In 2005, the Spitzer Space Telescope discovered a debris disk orbiting the star. The disk contains substantially more dust than the Solar System's asteroid belt. As of 2006, it has been confirmed that three extrasolar planets with minimum masses comparable to Neptune orbit the star, located interior to the debris disk. HD 69830 is an orange dwarf star of the spectral type K0V. The star has a mass of about 86 percent the Sun, 89 percent of its radius, and 45 percent of its luminosity. Containing 11 percent less iron than the Sun, recent age estimates indicated that the star is about 7 billion years old. HD 69830 is located about 41.0 light-years from the Sun, lying in the northeastern part of the constellation of Puppis (the Poop Deck). The star can be found east of Sirius, southwest of Procyon, northeast of Delta Canis Majoris, and north of Zeta Puppis. In 2005, the Spitzer Space Telescope detected a debris disk in the HD 69830 system consistent with being produced by an asteroid belt twenty times more massive than that in our own system. The belt was originally
    8.00
    1 votes
    159
    Zeta Aquarii

    Zeta Aquarii

    • Category: Star
    Zeta Aquarii (ζ Aqr, ζ Aquarii) is the Bayer designation for a binary, or possibly a triple star system; the central star of the "water jar" asterism in the equatorial constellation of Aquarius. The combined apparent visual magnitude of this system is 3.65, which is readily visible to the naked eye. Parallax measurements yield a distance estimate of around 92 light-years (28 parsecs) from Earth. Zeta Aquarii has the traditional name Sadaltager (or Altager), from the Arabic سعد التاجر sa‘d al-tājir "luck of the merchant". In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Achr al Achbiya (أجر ألأجبية - akhir al ahbiyah), which was translated into Latin as Postrema Tabernaculorum, meaning the end of luck of the homes (tents). This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent. In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii. Consequently, ζ Aquarii itself is known as 墳墓一 (Fén Mù yī, English: the First Star of Tomb.) Christian Mayer, director of the Mannheim Observatory, is considered the first to have
    8.00
    1 votes
    160
    16 Cygni

    16 Cygni

    16 Cygni or 16 Cyg is a triple star system approximately 70 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B. The parallax of the two brightest stars were measured as part of the Hipparcos astrometry mission. This yielded a parallax of 46.25 milliarcseconds for 16 Cygni A and 46.70 milliarcseconds for 16 Cygni B. Since the two components are associated, it is reasonable to assume they lie at the same distance, so the different parallaxes are a result of experimental error (indeed, when the associated parallax errors are taken into account, the ranges of the parallaxes overlap). Using the parallax of the A component, the distance is 21.6 parsecs. The parallax of the B component corresponds to a distance of 21.4 parsecs. 16 Cygni is a hierarchal triple system. Stars A and C form a close binary with a projected separation of 73 AU. The orbital elements of the A-C binary are currently unknown. At a distance of 860 AU from A is a third component designated 16 Cygni B. The orbit of
    7.00
    2 votes
    161
    Atlas

    Atlas

    • Category: Star
    Atlas is a triple star system in the Pleiades open cluster (M45). It is also known as 27 Tauri. The primary component, Atlas A, is a blue-white B-type giant with an apparent magnitude of +3.62. It is a spectroscopic binary whose components have magnitudes of +4.1 and +5.6. The binary makes one orbit every 1250 days. Atlas also has a dimmer magnitude +6.8 companion, Atlas B, at a separation of 0.4 arcseconds or at least 52 astronomical units away.
    7.00
    2 votes
    162
    Delta Boötis

    Delta Boötis

    • Category: Star
    Delta Boötis (δ Boo, δ Boötis) is a double star in the northern constellation Boötes. Based upon parallax measurements, it is located at a distance of approximately 121.8 light-years (37.3 parsecs) from the Earth. This star is sometimes called Princeps, meaning prince or prime in Latin. The origin of this name is unclear, although it usually appears in an astrological context. The It has an apparent visual magnitude of this star is 3.5, making it visible to the naked eye even during a Full Moon. In Chinese, 七公 (Qī Gōng), meaning Seven Excellencies, refers to an asterism consisting of δ Boötis, 42 Herculis, τ Herculis, φ Herculis, χ Herculis, ν Boötis and μ Boötis. Consequently, δ Boötis itself is known as 七公七 (Qī Gōng qī, English: the Seventh Star of Seven Excellencies.) This system consists of a pair of stars located in physical proximity to each other and sharing a similar motion through space, suggesting that they may form a binary star system. Based upon their angular separation and their distance, they have a projected physical separation of 3,800 Astronomical Units (AU). However, their separation along the line of sight from the Earth remains uncertain, so all that can really
    7.00
    2 votes
    163
    Gamma Capricorni

    Gamma Capricorni

    • Category: Star
    Gamma Capricorni (γ Cap, γ Capricorni) is a giant star in the constellation Capricornus. It has the traditional name Nashira, which comes from the Arabic سعد ناشرة - sa'd nashirah for "the lucky one" or "bearer of good news". In Chinese, 壘壁陣 (Lěi Bì Zhèn), meaning Line of Ramparts, refers to an asterism consisting of γ Capricorni, κ Capricorni, ε Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, λ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, γ Capricorni itself is known as 壘壁陣三 (Lěi Bì Zhèn sān, English: the Third Star of Line of Ramparts.) Because it is near the ecliptic, γ Capricorni can be occulted by the Moon, and (rarely) by planets. γ Capricorni is a blue-white A-type (A7III) giant star with a mean apparent magnitude of +3.69. It is approximately 139 light years from Earth. It is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies by 0.03 magnitudes. Nashira (AK-85) is once of United States navy ship. ukdj FGJYJ68J9HR[6OIJUYHITJYHJYT9JIHY6[IOJK4]H90W64JT0966[9UJYK
    7.00
    2 votes
    164
    Mu Cephei

    Mu Cephei

    • Category: Star
    Mu Cephei (μ Cep, μ Cephei), also known as Herschel's Garnet Star, is a red supergiant star in the constellation Cepheus. It is one of the largest and most luminous stars known in the Milky Way. It appears garnet red and is given the spectral class of M2 Ia. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The deep red color of Mu Cephei was noted by William Herschel, who described it as "a very fine deep garnet colour, such as the periodical star ο Ceti", and it is thus commonly known as Herschel's "Garnet Star". Giuseppe Piazzi called it Garnet sidus in his catalogue. An alternative name, Erakis, used in Antonín Bečvář's star catalogue, is probably due to confusion with Mu Draconis, which was previously called al-Rāqis [arˈraːqis] in Arabic. In 1848, English astronomer John Russell Hind discovered that it was variable. This variability was quickly confirmed by German astronomer Friedrich Wilhelm Argelander. Almost continual records of the star's variability have been maintained since 1881. A very luminous red supergiant, Mu Cephei is one of the largest stars visible to the naked eye, and in the entire
    7.00
    2 votes
    165
    Rho Cassiopeiae

    Rho Cassiopeiae

    • Category: Star
    Rho Cassiopeiae ( /ˌroʊ kæsiəˈpiː.iː/; ρ Cas, ρ Cassiopeiae) is a yellow hypergiant star in the constellation Cassiopeia. It is about 11,650 light-years (3,570 pc) away from Earth, yet can still be seen by the naked eye (in the Northern Hemisphere only), as it is 100,000 times as luminous as the Sun. On average, it has an absolute magnitude of −7.5, making it one of the most luminous stars known. Its surface diameter measures 450 times that of the Sun, or approximately 630,000,000 kilometers. Being a yellow hypergiant, it is one of the rarest types of stars, one of only seven in the Milky Way that are currently known, though it is not the only one in its constellation, which also includes V509 Cassiopeiae. Rho Cassiopeiae is a single star, and is categorized as a semiregular variable. The Bayer designation for this star was established in 1603 as part of the Uranometria, a star catalog produced by Johann Bayer. The star catalog by John Flamsteed published in 1712, which orders the stars in each constellation by their right ascension, gave this star the Flamsteed designation 7 Cassiopeiae. Rho Cassiopeiae is somewhat unstable in its luminosity. Its apparent magnitude is currently
    7.00
    2 votes
    166
    Tau Ceti

    Tau Ceti

    • Category: Star
    Tau Ceti (τ Cet, τ Ceti) is a star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years from the Solar System, it is a relatively nearby star. Tau Ceti is metal-deficient and so is thought to be less likely to host rocky planets. Observations have detected more than ten times as much dust surrounding Tau Ceti as is present in the Solar System. The star appears stable, with little stellar variation. Astrometric or radial velocity measurements have not yet detected companions around Tau Ceti, but given current search refinement, this only excludes substellar companions such as large brown dwarfs. Because of its debris disk, any planet orbiting Tau Ceti would face far more impact events than the Earth. Despite this hurdle to habitability, its solar analog (Sun-like) characteristics have led to widespread interest in the star. Given its stability, similarity and relative proximity to the Sun, Tau Ceti is consistently listed as a target for the Search for Extra-Terrestrial Intelligence (SETI), and it appears in some science fiction literature. Tau Ceti does not have a
    7.00
    2 votes
    167
    Theta Andromedae

    Theta Andromedae

    • Category: Star
    Theta Andromedae (θ And, θ Andromedae) is the Bayer designation for a binary star in the constellation Andromeda. It is approximately 310 light-years (95 parsecs) from Earth, with a visual magnitude of 4.6. On the Bortle Dark-Sky Scale, this makes it visible to the naked eye from outside urban regions. Theta Andromedae is a white A-type main sequence dwarf with an apparent magnitude of +4.61. It appears to be a binary star with a massive, possibly A-type secondary orbiting at a distance of around 1 astronomical unit. A fainter companion is separated from Theta Andromedae by 0.06 arcseconds. In Chinese, 天廄 (Tiān Jiù), meaning Celestial Stable, refers to an asterism consisting of θ Andromedae, ρ Andromedae and σ Andromedae. Consequently, θ Andromedae itself is known as 天廄一 (Tiān Jiù yī, English: the First Star of Celestial Stable.)
    7.00
    2 votes
    168
    Zeta Leonis

    Zeta Leonis

    • Category: Star
    Zeta Leonis (ζ Leo, ζ Leonis) is a third-magnitude star in the constellation Leo, the lion. It has the traditional name Adhafera (Aldhafera, Adhafara), from the Arabic الضفيرة al-ðafīrah "the braid/curl", a reference to its position in the lion's mane. It forms the second star (after Gamma Leonis) in the blade of "The Sickle", which is an asterism formed from the head of Leo. Adhafera is a giant star with a stellar classification of F0 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Its apparent magnitude is +3.44, making it relatively faint for a star that is visible to the naked eye. Nevertheless, it shines with 85 times the luminosity of the Sun. Adhafera has about three times the Sun's mass and six times the radius of the Sun. Parallax measurements from the Hipparcos satellite yield an estimated distance to Adhafera of 274 light-years (84 parsecs) from Earth. Adhafera forms a double star with an optical companion that has an apparent magnitude of 5.90. Known as 35 Leo, this star is separated from Adhafera by 325.9 arcseconds along a position angle of 340°. The two stars do not form a binary star
    7.00
    2 votes
    169
    Castor

    Castor

    • Category: Star
    Castor (α Gem, α Geminorum, Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the night sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum (Pollux). Castor is 49.8 light years away from Earth. Castor was discovered to be a visual binary in 1678, with the magnitude of its components being 2.0 and 2.9 (the combined magnitude is 1.58). The separation of the components is about 6", and the period of revolution is around 467 years. Each of the components of Castor is itself a spectroscopic binary, making Castor a quadruple star system. Castor has a faint companion separated from it by about 72" but having the same parallax and proper motion; this companion is an eclipsing binary system with a period slightly less than 1 day, and it is one of only a few known eclipsing binary systems where both companions are class M dwarf stars. Castor can thus be considered to be a sextuple star system, with six individual stars gravitationally bound together. Component C has the variable star designation YY Geminorum. Castor and Pollux are the two "heavenly twin" stars that give the constellation
    6.00
    3 votes
    170
    Earth

    Earth

    • Category: Planet
    • Artificial satellites: Sputnik 1
    Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the world, the Blue Planet, or by its Latin name, Terra. Earth formed approximately 4.54 billion years ago by accretion from the solar nebula, and life appeared on its surface within one billion years. The planet is home to millions of species, including humans. Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer, which together with Earth's magnetic field blocks harmful solar radiation, thus permitting formerly ocean-confined life to move safely to land. The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist. Estimates on how much longer the planet will to be able to continue to support life range from 500 million years, to as long as 2.3 billion years. Earth's crust is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods
    6.00
    3 votes
    171
    Gomez's Hamburger

    Gomez's Hamburger

    • Category: Star
    Gomez's Hamburger is believed to be a young star surrounded by a protoplanetary disk. It was initially identified as a planetary nebula (i.e. an old dying star), and its distance therefore wrongly estimated to be approximately 6500 light-years away from planet Earth. However, recent results suggest that this object is a young star surrounded by a protoplanetary disk whose distance is only around 900 light-years away. It was discovered in 1985 on sky photographs obtained by Arturo Gomez, support technical staff at the Cerro Tololo Inter-American Observatory near Vicuña, Chile. The photos suggested that there was a dark band across the object, but its exact structure was difficult to determine because of the atmospheric turbulence that hampers all images taken from the ground. The star itself has a surface temperature of approximately 10,000 °C (18,000 °F). The "hamburger buns" are light reflecting off dust, and the "petit paté" is the dark band of dust in the middle.
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    3 votes
    172
    Lambda Scorpii

    Lambda Scorpii

    • Category: Star
    Lambda Scorpii (λ Sco, λ Scorpii) is the second brightest star system in the constellation Scorpius, and one of the brightest stars in the nighttime sky. It has the Bayer designation λ despite being the second brightest in its constellation. It has the traditional name Shaula, which comes from the Arabic الشولاء al-šawlā´ meaning the raised [tail], as it is found in the tail of the scorpion (Scorpius). It is known as 尾宿八 (the Eighth Star of the Tail) in Chinese. Lambda Scorpii is a multiple star which was 300 mlight years away from the earth with three visible components. The first, Lambda Scorpii A, is classified as a B-type subgiant. The 15th magnitude Lambda Scorpii B has a separation of 42 arcseconds from component A, while the 12th magnitude Lambda Scorpii C is 95 arcseconds from A. It is not known whether or not these components are physically associated with component A. If they both were, B would be approximately 7500 Astronomical Units and C approximately 17,000 AU (0.27 light years) from A. Spectroscopic and interferometric observations have shown that A is actually a triple system consisting of two B-type stars and a pre–main sequence star. The primary star is also a
    6.00
    3 votes
    173
    31 Camelopardalis

    31 Camelopardalis

    • Category: Star
    31 Camelopardalis is an eclipsing spectroscopic binary in the constellation Camelopardalis. It is approximately 405 light years from Earth. The binary system is classified as a white A-type main sequence dwarf with a mean apparent magnitude of +5.20. Both component stars are detached main sequence stars which do not fill their Roche lobes. Because the components regularly eclipse each other, 31 Camelopardalis is classified as a variable star and its brightness varies from magnitude +5.12 to +5.29 with a period of 2.93 days, which is the orbital period of the binary.
    5.67
    3 votes
    174
    Cha 110913-773444

    Cha 110913-773444

    • Category: Star
    Cha 110913-773444 (sometimes abbreviated Cha 110913) is an astronomical object surrounded by what appears to be a protoplanetary disk. There is no consensus yet among astronomers whether to classify the object as a sub-brown dwarf (with planets) or a rogue planet (with moons). Cha 110913-773444 was discovered in 2004 by Kevin Luhman and others at Pennsylvania State University using the Spitzer Space Telescope and the Hubble Space Telescope, as well as two earthbound telescopes in Chile.
    5.67
    3 votes
    175
    Lambda Cassiopeiae

    Lambda Cassiopeiae

    • Category: Star
    Lambda Cassiopeiae (λ Cas, λ Cassiopeiae) is a binary star in the constellation Cassiopeia. The system has a combined apparent magnitude of +4.74 and is approximately 355 light years from Earth. Both components are blue-white B-type main sequence dwarfs. The brighter, λ Cassiopeiae A, has an apparent magnitude of +5.5, while its companion, λ Cassiopeiae B, has an apparent magnitude of +5.8. The two stars are separated by 0.6 arcseconds and complete one orbit around their common centre of mass once every 640 years.
    5.67
    3 votes
    176
    Mira B

    Mira B

    • Category: Star
    Mira B, also known as VZ Ceti, is the companion star to the variable star Mira. Suspected as early as 1918, it was visually confirmed in 1923 by Robert Grant Aitken, and has been observed more or less continually since then, most recently by the Chandra X-Ray Observatory. Its orbit around Mira is poorly known; the most recent estimate listed in the Sixth Orbit Catalog of Visual Binary Stars gives an orbital period of roughly 500 years, with a periastron around the year 2285. Assuming the distance in the Hipparcos catalog and orbit are correct, Mira A and B are separated by an average of 100 AU. Long-known to be erratically variable itself, its fluctuations seem to be related to its accretion of matter from Mira's stellar wind, which makes it a symbiotic star. In January 2007, astronomers at the Keck Observatory announced the discovery of a protoplanetary disk around Mira B. Discovered via infrared data, the disk is apparently derived from captured material from Mira itself; Mira B accretes as much as one percent of the matter lost by its primary. Though planetary formation is perhaps unlikely as long as the disk is in active accretion, it may proceed apace once Mira A completes its
    5.67
    3 votes
    177
    Pistol Star

    Pistol Star

    • Category: Star
    The Pistol Star is a blue hypergiant and is one of the most luminous known stars in the Milky Way Galaxy. It is one of many massive young stars in the Quintuplet cluster in the Galactic Center region. The star owes its name to the shape of the Pistol Nebula, which it illuminates. It is located approximately 25,000 light years from Earth in the direction of Sagittarius. It would be visible to the naked eye as a fourth magnitude star, if it were not for the interstellar dust that completely hides it from view in visible light. The Pistol Star was discovered by the Hubble Space Telescope in the early 1990s. The star is thought to have ejected almost 10 solar masses of material in giant outbursts perhaps 4,000 to 6,000 years ago (as observed from Earth). Its stellar wind is over 10 billion times stronger than the Sun's. Its exact age and future are not known, but it is expected to end in a brilliant supernova or hypernova in 1 to 3 million years. Some astronomers conjecture that its large mass may be related to its location near the Galactic Center, since the star formation process there may favor massive objects. Early reports suggested that it might be the most luminous star known,
    5.67
    3 votes
    178
    Sigma Octantis

    Sigma Octantis

    • Category: Star
    Sigma Octantis (σ Oct, σ Octantis) is a magnitude 5.6 star in the constellation Octans most notable for being the current South Star. Sigma Octantis is approximately 270 light years from Earth, and is classified as a giant, with a spectral type of F0 III. It is a Delta Scuti variable, with magnitude varying by about 0.03 magnitudes over 2.3 hours. Sigma Octantis is the dimmest star to be represented on a national flag. It appears on the flag of Brazil, symbolising the Brazilian Federal District. Its position near the southern celestial pole makes it the southern hemisphere's pole star, whence its occasional name, Polaris Australis. Sigma Octantis is the southern pole star, whose counterpart is Polaris, the current North Star. To an observer in the southern hemisphere, Sigma Octantis appears almost motionless and all the other stars in the Southern sky appear to rotate around it. It is part of a small "half hexagon" shape. It is over a degree away from the true south pole, and the south celestial pole is moving away from it due to precession of the equinoxes. At magnitude 5.6, Sigma Octantis is barely visible to the naked eye, making it a rather poor pole star, especially by
    5.67
    3 votes
    179
    Deimos

    Deimos

    • Category: Natural satellite
    Deimos is a Mars moon with an average radius of 6.2 kilometres (3.9 mi), and an escape velocity of 5.6 m/s (20 km/h). It is the smaller and outer of Mars's two known moons, the other being Phobos. 23,460 km (14,580 mi) distant from Mars, Deimos takes 30.3 hours to orbit the planet at an orbital velocity of 1.35 km/s. Its systematic designation is Mars II. In English Deimos is pronounced  /ˈdaɪməs/ DY-məs; also /ˈdiːməs/ DEE-məs; Greek: Δείμος; also DAY-moce or DEE-moce. Deimos was discovered by Asaph Hall, Sr. at the United States Naval Observatory in Washington, D.C on August 12, 1877, at about 07:48 UTC (given in contemporary sources as "August 11 14:40" Washington mean time, using an astronomical convention of beginning a day at noon, so 12 hours must be added to get the actual local mean time). Hall also discovered Phobos on August 18, 1877, at about 09:14 GMT, after deliberately searching for Martian moons. It is named after Deimos, a figure representing dread in Greek Mythology. The names, at first spelled Phobus and Deimus, were suggested by Henry Madan (1838–1901), Science Master of Eton, from Book XV of the Iliad, where Ares (the Roman god Mars) summons Dread (Deimos) and
    6.50
    2 votes
    180
    Delta Cancri

    Delta Cancri

    • Category: Star
    Delta Cancri (δ Cnc, δ Cancri) is an orange giant star approximately 180 light-years away in the constellation Cancer. It has the traditional name Asellus Australis which in Latin means "southern donkey colt". It also has the longest of all known star names, Arkushanangarushashutu, derived from ancient Babylonian which means "the southeast star in the Crab". In Chinese, 鬼宿 (Guǐ Su), meaning Ghost (asterism), refers to an asterism consisting of δ Cancri, θ Cancri, η Cancri and γ Cancri. Consequently, δ Cancri itself is known as 鬼宿四 (Guǐ Su sì, English: the Fourth Star of Ghost.) Since it is near the ecliptic, it can be occulted by the Moon and very rarely by planets. Delta Cancri was involved in the first recorded occultation by Jupiter: Delta Cancri also marks the famous open star cluster Praesepe (or the Beehive Cluster, also known as Messier 44). In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos' Prognostica reveals: The meaning of this verse is that if Asellus Borealis or Gamma Cancris is hidden by clouds, the wind will be from the south and that situation will be reversed if Arkushanangarushashutu is obscured. There is some doubt however
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    2 votes
    181
    Eta Boötis

    Eta Boötis

    • Category: Star
    Eta Boötis (η Boo, η Boötis) is a star in the constellation Boötes. It has the traditional names Muphrid and Saak, and the Flamsteed designation 8 Boötis. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The name Muphrid is from the Arabic مفرد الرامح mufrid ar-rāmiħ "the (single) one of the lancer". In Chinese, 右攝提 (Yòu Niè Dī), meaning "the Right Conductor", refers to an asterism consisting of Eta Boötis, Tau Boötis and Upsilon Boötis. Consequently, Eta Boötis itself is known as 右攝提一 (Yòu Niè Dī yī, English: the First Star of the Right Conductor.) In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Ramih al Ramih (رمح الرامح - rumḥ al rāmiḥ), which was translated into Latin as Lancea Lanceator, possibly meaning the lance of the lancer. This star is a subgiant that has begun the process of evolving from a main sequence star into a red giant. It has about 1.7 times the mass of the Sun and 2.7 times the Sun's radius. The estimated age of this star is about 2.7 billion years. Based on its spectra, Eta Boötis has a significant excess of elements heavier than helium. In
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    2 votes
    182
    HD 209458

    HD 209458

    • Category: Star
    HD 209458 is an 8th magnitude star in the constellation Pegasus. It is very similar to our Sun, and it is classified as a yellow dwarf (spectral class G0 V). Because it is located at a distance of about 150 light years, it is not visible to the unaided eye. With good binoculars or small telescope it should be easily detectable. In 1999 two teams working independently (one team consisted of astronomers at the Geneva Observatory, the Harvard-Smithsonian Center for Astrophysics, and the Wise Observatory; the second group was the California and Carnegie Planet Search team) discovered an extrasolar planet orbiting the star by using the radial velocity planet search method. Soon after the discovery, separate teams led by David Charbonneau and Gregory W. Henry were able to detect a transit of the planet across the surface of the star making it the first known transiting extrasolar planet. The planet received the designation HD 209458 b. Because the planet transits the star, the star is dimmed by about 2% every 3.5 days making it an extrinsic variable. The variable star designation for HD 209458 is V376 Pegasi. It is the prototype of the variable class "EP" in the General Catalogue of
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    2 votes
    183
    Moon

    Moon

    • Category: Natural satellite
    • Locations: Tracy's Rock
    The Moon (Latin: luna) is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. It is the largest natural satellite of a planet in the Solar System relative to the size of its primary, having 27% the diameter and 60% the density of Earth, resulting in ⁄81 its mass. The Moon is the second densest satellite after Io, a satellite of Jupiter. The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a reflectance similar to that of coal. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly
    6.50
    2 votes
    184
    Mu Geminorum

    Mu Geminorum

    • Category: Star
    Mu Geminorum (μ Gem, μ Geminorum) is the Bayer designation for a star in the northern constellation of Gemini. It has the traditional name Tejat Posterior, which means back foot, because it is the foot of Castor, one of the Gemini twins. This name was formerly applied to an asterism consisting of this star, along with γ Gem (Alhena), ν Gem, η Gem (Tejat Prior), and ξ Gem (Alzirr). The names Calx (Latin, meaning heel), Pish Pai (from the Persian Pīshpāy, پیش‌پای, meaning foreleg), and Nuhatai (from Arabic Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump") have also been applied to Mu Geminorum. In Chinese, 井宿 (Jǐng Su), meaning Well (asterism), refers to an asterism consisting of μ Geminorum, γ Geminorum, ν Geminorum, ξ Geminorum, ε Geminorum, 36 Geminorum, ζ Geminorum and λ Geminorum. Consequently, μ Geminorum itself is known as 井宿一 (Jǐng Su yī, English: the First Star of Well.) Mu Geminorum has an average apparent visual magnitude of 2.9, which makes it the fourth brightest member of Gemini. From parallax measurements made during the Hipparcos mission, the distance to this star is roughly 230 light-years (71 parsecs). Its visual magnitude is diminished by 0.07 as a result of
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    185
    Nu Andromedae

    Nu Andromedae

    • Category: Star
    Nu Andromedae (Nu And, ν Andromedae, ν And) is a binary star in the constellation Andromeda. The system has an apparent visual magnitude of 4.5, which is bright enough to be seen with the naked eye. It is approximately 620 light-years (190 parsecs) from Earth. Situated just over a degree to the west of this star is the Andromeda Galaxy. Nu Andromedae is spectroscopic binary system with a nearly circular orbit that has a period of 4.2828 days. The primary component is a B-type main sequence star with a stellar classification of B5 V. The fainter secondary has a classification of F8 V, which makes it an F-type main sequence star. The pair are about 63 million years old. In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ν Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, π Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, ν Andromedae itself is known as 奎宿七 (Kuí Sù qī, English: the Seventh Star of Legs.)
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    186
    PSR B1620-26 b

    PSR B1620-26 b

    PSR B1620-26 b is an extrasolar planet located approximately 12,400 light-years away from Earth in the constellation of Scorpius (the Scorpion). It bears the unofficial nicknames "Methuselah" and "the Genesis planet" due to its extreme age and a few popular sources refer to this object as "PSR B1620-26 c" (see below for discussion). The planet is in a circumbinary orbit around the two stars of PSR B1620-26 (which comprises a pulsar (PSR B1620-26 A) and a white dwarf (WD B1620-26)). The planet is the oldest known extrasolar planet, believed to be about 12.7 billion years old. While the designation PSR B1620-26 b is not used in any scientific papers, the planet is listed in the SIMBAD database as PSR B1620-26 b. Some popular sources use the designation PSR B1620-26 c to refer to the planet, presumably under the logic that since the A and B designations are used for the two stars it orbits, the planetary designations should start at "c". This usage is not supported in the scientific literature, nor does this designation appear in the SIMBAD database. As of November 2008, the only other known circumbinary planets orbit the eclipsing binary HW Virginis, however the discovery paper in
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    187
    11 Camelopardalis

    11 Camelopardalis

    • Category: Star
    11 Camelopardalis or BV Camelopardalis is a star system in the constellation Camelopardalis. It forms a double star with 12 Camelopardalis, which is only 3 arcminutes away. 11 Camelopardalis is a blue-white B-type main sequence dwarf with a mean apparent magnitude of +5.22. It is classified as a Gamma Cassiopeiae type variable star and its brightness varies by 0.07 magnitudes with a period of a few hours. It is approximately 671 light years from Earth.
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    188
    44 Boötis

    44 Boötis

    • Category: Star
    44 Boötis or i Boötis is a triple star system in the constellation Boötes. It is approximately 41.6 light years from Earth. The primary component, 44 Boötis A, is a yellow-white F-type main sequence dwarf with a mean apparent magnitude of +4.83. The companion component, 44 Boötis B, is a W Ursae Majoris variable spectroscopic binary. The brightness of the binary varies from magnitude +5.8 to +6.40 with a period of 6.43 hours. The components of the eclipsing binary are separated by 0.008 Astronomical Units, roughly 3 times the distance of the Moon from Earth. Recent analysis in timing variations for 44 Bootis B would suggest the presence of a third body orbiting the W Ursae Majoris-type eclipsing binary with likely substellar mass. Its minimum mass is estimated at 48 times that of Jupiter and the orbital separation at 10.73 AUs (a bit farther away than Saturn in the Solar System). So far unconfirmed, such an object seems unstable considering the system's architecture, with 44 Bootis B-C getting as close as 26.6 AUs to 44 Bootis A, unless it is locked in some kind of peculiar configuration and inclination.
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    1 votes
    189
    Achernar

    Achernar

    • Category: Star
    Achernar (α Eri, α Eridani, Alpha Eridani), sometimes spelled Achenar, is the brightest star in the constellation Eridanus and the ninth-brightest star in the night sky. Of the top ten apparent brightest stars (excluding our Sun)—Sirius, Canopus, Alpha Centauri, Arcturus, Vega, Capella, Rigel, Procyon, Achernar and Betelgeuse—Achernar is the hottest and bluest. It lies at the southern tip of the constellation. Achernar is a bright, blue star with about six to eight solar masses. As determined by the Hipparcos astrometry satellite, it is approximately 139 light-years (43 pc) away. It is a main sequence star with a stellar classification of B6 Vep, but is about 3,150 times more luminous than the Sun. Achernar is in the deep southern sky and never rises above the horizon beyond 33°N, roughly the latitude of Dallas, Texas. Achernar is best seen from the southern hemisphere in November; it is circumpolar below 33°S. Until about March 2000, Achernar and Fomalhaut were the two first-magnitude stars furthest in angular distance from any other first-magnitude star in the celestial sphere. Antares, in the constellation of Scorpius, is now the most isolated first-magnitude star, although
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    190
    HD 102117

    HD 102117

    • Category: Star
    HD 102117 is a magnitude 7 yellow dwarf star (spectral type G6V) about 130 light years from Earth in the constellation of Centaurus. Although it is cooler than our Sun it is brighter and thus more evolved. This star is too dim to be seen without binoculars or a small telescope. In 2004, the Anglo-Australian Planet Search announced a planet orbiting the star. A short time later the HARPS team also announced the presence of a planet around this star. Both groups detected this planet with the radial velocity method.
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    1 votes
    191
    HD 179949

    HD 179949

    • Category: Star
    HD 179949 is a 6th magnitude star in the constellation of Sagittarius. It is a yellow-white dwarf (spectral class F8 V), a type of star hotter and more luminous than our Sun. The star is located at 88 light years from Earth and might be visible under exceptionally good conditions to an experienced observer without technical aid; usually binoculars are needed. The only known planet orbiting HD 179949 is HD 179949 b.
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    1 votes
    192
    Upsilon2 Cassiopeiae

    Upsilon2 Cassiopeiae

    • Category: Star
    Upsilon Cassiopeiae (υ Cas, υ Cassiopeiae) is a star in the constellation Cassiopeia. υ Cassiopeiae is a yellow G-type giant with an apparent magnitude of +4.62. It is approximately 205.9 light years from Earth.
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    193
    Vega

    Vega

    • Category: Star
    Vega (α Lyr, α Lyrae, Alpha Lyrae) is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus. It is a relatively close star at only 25 light-years from Earth, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood. Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Vega was the northern pole star around 12,000 BC and will be so again around AD 13,727 when the declination will be +86°14'. Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. It was one of the first stars whose distance was estimated through parallax measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system. Vega is only about a tenth of the age of the Sun, but since it is 2.1 times as massive its expected lifetime is also one tenth of that of the Sun; both stars are at present approaching the
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    1 votes
    194
    Zeta Antliae

    Zeta Antliae

    • Category: Star
    Zeta Antliae is the Bayer designation for a binary star system in the southern constellation of Antlia. Based upon parallax measurements, the pair are located at a distance of roughly 410 light-years (130 parsecs) from Earth. Both components are rapidly rotating A-type main sequence stars. They have apparent magnitudes of +6.20 and 7.01 and are separated by 8.042 arcseconds. The apparent magnitude of the combined system is +5.76, which is bright enough to be seen with the naked eye in suitably dark skies.
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    195
    Beta Lyrae

    Beta Lyrae

    • Category: Star
    Beta Lyrae (β Lyr, β Lyrae) is a binary star system approximately 960 light-years (290 parsecs) away in the constellation Lyra. Beta Lyrae has the traditional name Sheliak (occasionally Shelyak), from الشلياق šiliyāq, the Arabic name of the constellation Lyra. The Bayer designation for this star was given by the German astronomer Johann Bayer with the publication of his star atlas Uranometria in 1603. It was given the Flamsteed designation 10 Lyrae by John Flamsteed in 1712 with the first publication of his star catalogue. The variable luminosity of this system was discovered in 1784 by the British amateur astronomer John Goodricke. Beta Lyrae is a semidetached binary system made up of a stellar class B7II primary star and a secondary that is probably also a B-type star. The brighter, less massive star (B7II) in the system was once the more massive member of the pair, which caused it to evolve away from the main sequence first and become a giant star. Because the pair are in a close orbit, as this star expanded into a giant it filled its Roche lobe and transferred most of its mass over to its companion. The secondary, now more massive star is surrounded by an accretion disk from
    5.33
    3 votes
    196
    Eta Arae

    Eta Arae

    • Category: Star
    Eta Arae (η Ara, η Arae) is the Bayer designation for a single star in the southern constellation of Ara. It is approximately 299 light-years (92 parsecs) from Earth and is visible to the naked eye with an apparent visual magnitude of 3.76. The spectrum of this star matches a stellar classification of K5 III, indicating that, at an estimated age of seven billion years, it has reached the giant star stage of its evolution. With a mass nearly the same as the Sun, it has an outer envelope that has expanded to nearly 56 times the Sun's radius. The star is now spinning so slowly that it takes more than eleven years to complete a single rotation. Eta Arae is radiating energy into space at an effective temperature of 3,886 K, giving it the orange-hued glow of a K-type star. It has a 14th magnitude optical companion, located 25.7 arcseconds away.
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    197
    Gliese 229

    Gliese 229

    • Category: Star
    Gliese 229 (also written as Gl 229 or GJ 229) is a red dwarf star about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun, 69% of the Sun's radius, and a very low projected rotation velocity of 1 km/s at the stellar equator. The star is known to be a low activity flare star, which means it undergoes random increases in luminosity because of magnetic activity at the surface. The spectrum shows emission lines of calcium in the H and K bands. The emission of X-rays has been detected from the corona of this star. These may be caused by magnetic loops interacting with the gas of the star's outer atmosphere. No large-scale star spot activity has been detected. In 1994 a substellar companion was imaged and it was confirmed in 1995. Gliese 229B is a brown dwarf orbiting the star; although it is too small to sustain hydrogen-burning nuclear fusion, with a mass of 20 to 50 times that of Jupiter (0.02 to 0.05 solar masses) it is still too massive to be a planet. Gliese 229B was the first confirmed substellar-mass object. This object has a surface temperature of 950 K. The space velocity components of this star are U = +12, V = –11 and W = –12 km/s. The orbit of
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    3 votes
    198
    61 Cygni

    61 Cygni

    • Category: Star
    61 Cygni, sometimes called Bessel's Star or Piazzi's Flying Star, is a binary star system in the constellation Cygnus. It consists of a pair of K-type dwarf stars that orbit each other in a period of about 659 years, forming a visual binary. At fifth and sixth apparent magnitudes, they are among the least conspicuous stars visible in the night sky to an observer without an optical instrument. 61 Cygni first attracted the attention of astronomers because of its large proper motion. In 1838, Friedrich Wilhelm Bessel measured its distance from Earth at about 10.4 light years, very close to the actual value of about 11.4 light years; this was the first distance estimate for any star other than the Sun, and first star to have its stellar parallax measured. Over the course of the twentieth century, several different astronomers reported detections of a massive planet orbiting one of the two stars, but recent high-precision radial velocity observations have shown that all such claims were erroneous. To date, no planets have been confirmed in this system and all of the past claims are now considered spurious. The large proper motion of 61 Cygni was first demonstrated by Giuseppe Piazzi in
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    199
    Epsilon Ursae Majoris

    Epsilon Ursae Majoris

    • Category: Star
    Epsilon Ursae Majoris (Epsilon UMa, ε Ursae Majoris, ε UMa) is the brightest star in the constellation Ursa Major (despite its Bayer designation being merely "epsilon"), and at magnitude 1.76 is the thirty-first brightest star in the sky. It has the traditional name Alioth. It is the star in the tail of the bear closest to its body, and thus the star in the handle of the Big Dipper closest to the bowl. It is also a member of the large and diffuse Ursa Major moving group. Historically, the star was frequently used in celestial navigation in the maritime trade, because it is listed as one of the 57 navigational stars. According to Hipparcos, Alioth is 81 light years (25 parsecs) from Earth. Its spectral type is A0p; the "p" stands for peculiar, as the spectrum of its light is characteristic of an Alpha2 Canum Venaticorum variable. Alioth, as a representative of this type, may harbor two interacting processes. First, the star's strong magnetic field separating different elements in the star's hydrogen 'fuel'. In addition, a rotation axis at an angle to the magnetic axis may be spinning different bands of magnetically-sorted elements into the line of sight between Alioth and the Earth.
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    2 votes
    200
    Gamma Canis Minoris

    Gamma Canis Minoris

    • Category: Star
    Gamma Canis Minoris (γ CMi, γ Canis Minoris) is a binary star in the constellation Canis Minor. It is approximately 398 light years from Earth. γ Canis Minoris is an orange K-type giant with an apparent magnitude of +4.34. It is a spectroscopic binary, and it has an unresolved companion which has an orbital period of 389 days. Its orange colour is obvious when seen through binoculars.
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    2 votes
    201
    Psi Cassiopeiae

    Psi Cassiopeiae

    • Category: Star
    Psi Cassiopeiae (ψ Cas, ψ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is approximately 193.1 light years from Earth. The primary component, ψ Cassiopeiae A, is an orange K-type giant with an apparent magnitude of +5.0; it is a double star, designated CCDM J01259+6808AB, with a fourteenth magnitude star (component B) located 3 arcseconds from the primary. Located about 25 arcseconds distant there is a 9.8 magnitude optical companion CCDM J01259+6808CD, designated ψ Cassiopeiae B in older star catalogues, which is itself another double; CD comprises a 9.4 magnitude component C and a 10 magnitude component D.
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    2 votes
    202
    Delta Antliae

    Delta Antliae

    • Category: Star
    Delta Antliae (δ Ant, δ Antliae) is the Bayer designation for a binary star system in the southern constellation of Antlia. The combined apparent visual magnitude of the system is +5.57, allowing it to be viewed from the suburbs with the naked eye. Judging by the parallax shift of this system, is located at a distance of roughly 480 light-years (150 parsecs) from Earth. The system is reduced in magnitude by 0.03 due to extinction caused by intervening gas and dust. The primary component of the system has a stellar classification of B9.5 V, indicating that it is a B-type main sequence star. The companion is an F-type main sequence star with a classification of F9 Ve, where the 'e' indicates that there are emission lines in the spectrum. The two stars are separated by 11 arcseconds. Delta Antliae A, the brighter member of this system, has an estimated 3.4 times the mass of the Sun. It is radiating around 200 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 11,117 K. At this heat, it shines with the characteristic blue-white hue of a B-type star.
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    3 votes
    203
    Sigma Scorpii

    Sigma Scorpii

    • Category: Star
    Sigma Scorpii (σ Sco, σ Scorpii) is a star system in the constellation Scorpius. It has the traditional name Al Niyat, although this name is sometimes also applied to Tau Scorpii, or to the asterism formed by both Sigma and Tau. This system has a combined apparent visual magnitude of +2.88, making it one of the brighter members of the constellation, although greatly outshone by its neighbor Antares. Based upon parallax measurements made during the Hipparcos mission, the distance to Sigma Scorpii is roughly 696 light years (214 parsecs). North et al. (2007) computed a more accurate estimate of 568+75 −59 light years (174+23 −18 parsecs). The brightest component of the system is a double-lined spectroscopic binary, which means that the pair has not been resolved using a telescope. Instead, their orbit is determined by changes in their combined spectrum caused by the Doppler shift. This indicates that the pair complete an orbit every 33.01 days and have an orbital eccentricity of 0.32. The primary component of the spectroscopic binary, σ Scorpii A, is an evolved giant star with a stellar classification of B1 III. It has around 18 times the mass of the Sun and 12 times the Sun's
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    3 votes
    204
    Beta Andromedae

    Beta Andromedae

    • Category: Star
    Beta Andromedae (Beta And, β And, β Andromedae) is the Bayer designation for a prominent star in the northern constellation of Andromeda. It has the traditional name Mirach, which is also spelled Merach, Mirac, Mirak. β Andromedae is located northeast of the Great Square of Pegasus and is theoretically visible to all observers north of 54° S. The galaxy NGC 404, also known as Mirach's Ghost, is visible seven arc-minutes away. This star has an average apparent visual magnitude of 2.05, which makes it the brightest star in the constellation. However, the luminosity varies slightly from magnitude +2.01 to +2.10. Based upon parallax measurements, it is located at a distance of roughly 197 light-years (60 parsecs) from Earth. The apparent magnitude of this star is reduced by 0.06 from extinction caused by the gas and dust along the line of sight. Beta Andromedae is a red giant with a stellar classification of M0 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is suspected of being a semiregular variable star whose apparent visual magnitude varies from +2.01 to +2.10. At this stage of the star's evolution,
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    2 votes
    205
    Beta Canis Minoris

    Beta Canis Minoris

    • Category: Star
    Beta Canis Minoris (β CMi, β Canis Minoris) is a star in the constellation of Canis Minor. In the night sky it is notable for its proximity to the prominent star Procyon. It has the traditional name Gomeisa, which comes from the Arabic al-ghumaisa’ "the bleary-eyed (woman)", short for مرزم الغميصاء mirzam al-ghumaisa’ "girdle of the bleary-eyed one". In Arabic, the short form would be identical with the name of Procyon. In Chinese, 南河 (Nán Hé), meaning South River, refers to an asterism consisting of β Canis Minoris, Procyon and ε Canis Minoris. Consequently, β Canis Minoris itself is known as 南河二 (Nán Hé èr, English: the Second Star of South River.) From parallax measurements, the distance to this star is about 162 light-years (50 parsecs). It has an apparent visual magnitude of 2.89, making it easily visible to the naked eye. Beta Canis Minoris has about 3.5 times the Sun's mass and is rotating rapidly with a projected rotational velocity of 210 km s, which gives a lower bound on the azimuthal rotational velocity along the star's equator. The actual rotation rate may be about once per day. The stellar classification of this star is B8 Ve. A luminosity class V star belongs on the
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    206
    Beta Pictoris

    Beta Pictoris

    • Category: Star
    Beta Pictoris (β Pic, β Pictoris) is the second brightest star in the constellation Pictor. It is located 63.4 light years from our solar system, and is 1.75 times as massive and 8.7 times as luminous as the Sun. The Beta Pictoris system is very young, only 8–20 million years old, although it is already in the main sequence stage of its evolution. Beta Pictoris is the title member of the Beta Pictoris moving group, an association of young stars which share the same motion through space and have the same age. Beta Pictoris shows an excess of infrared emission compared to normal stars of its type, which is caused by large quantities of dust near the star. Detailed observations reveal a large disk of dust and gas orbiting the star, which was the first debris disk to be imaged around another star. In addition to the presence of several planetesimal belts and cometary activity, there are indications that planets have formed within this disk and that the processes of planet formation may still be ongoing. Material from the Beta Pictoris debris disk is thought to be the dominant source of interstellar meteoroids in our solar system. The European Southern Observatory (ESO) has confirmed
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    207
    Betelgeuse

    Betelgeuse

    • Category: Star
    Betelgeuse (/ˈbiːtəldʒuːz/ or /ˈbɛtəldʒuːz/), also known by its Bayer designation Alpha Orionis (α Orionis, α Ori), is the eighth brightest star in the night sky and second brightest in the constellation of Orion, outshining Rigel (Beta Orionis) only rarely. Distinctly reddish, it is a semiregular variable star whose apparent magnitude varies between 0.2 and 1.2, the widest range of any first-magnitude star. Betelgeuse is one of three stars which make up the Winter Triangle and marks the center of the Winter Hexagon. The star's name is thought to be derived from the Arabic يد الجوزاء Yad al-Jauzā' meaning "the Hand of al-Jauzā'", i.e., Orion, with mistransliteration into medieval Latin leading to the first character y being misread as a b. The star is classified as a red supergiant of spectral type M2Iab and is one of the largest and most luminous known stars. If it were at the center of the Solar System its surface would extend past the asteroid belt, possibly to the orbit of Jupiter and beyond, wholly engulfing Mercury, Venus, Earth and Mars. Its distance was estimated in 2008 at 640 light-years from Earth, yielding a mean absolute magnitude of about −6.02. Less than 10 million
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    208
    Gamma1 Caeli

    Gamma1 Caeli

    • Category: Star
    Gamma Caeli (γ Cae, γ Caeli) is a double star in the constellation Caelum. It is approximately 185 light years from Earth. The brighter component is an orange K-type giant with an apparent magnitude of +4.55. The companion is an eighth magnitude star located 3.1 arcseconds away.
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    2 votes
    209
    Regulus

    Regulus

    • Category: Star
    Regulus (α Leo, α Leonis, Alpha Leonis) is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars that are organized into two pairs. The spectroscopic binary Regulus A consists of a blue-white main-sequence star and its companion, which has not yet been directly observed, but is probably a white dwarf star. Located farther away is the pair Regulus B and Regulus C, which are dim main-sequence stars. Of the brightest stars in the sky, Regulus is closest to the ecliptic, and is regularly occulted by the Moon. Occultations by the planets Mercury and Venus are also possible but rare, as are occultations by asteroids. The last occultation of Regulus by a planet was on July 7, 1959, by Venus. The next will occur on October 1, 2044, also by Venus. Other planets will not occult Regulus over the next few millennia because of their node positions. Regulus is expected to be occulted by the asteroid 163 Erigone on March 20, 2014. This event will be visible along a path about 40 miles wide from New York City to Oswego in the United States, and extending
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    2 votes
    210
    YZ Ceti

    YZ Ceti

    • Category: Star
    YZ Ceti is a red dwarf star in the constellation Cetus. Although it is relatively close to the Sun at just 12 light years, this star cannot be seen with the naked eye. It is classified as a flare star that undergoes intermittent fluctuations in luminosity. YZ Ceti is only about 8.5% the mass of our Sun, and is normally less than 1/5,000th as luminous. This star is unusually close to Tau Ceti, a star of spectral class G8. The two are only about 1.6 light years apart, a little more than a third of the distance from the Sun to our nearest neighbor, Proxima Centauri.
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    2 votes
    211
    AB Pictoris

    AB Pictoris

    • Category: Star
    AB Pictoris (abbreviated AB Pic, also catalogued as HD 44627) is a K-type star, approximately 148 light-years away in the constellation of Pictor. It has been identified as a member of the young (30 million years old) Tucana–Horologium association. The star has also been classified as a BY Draconis variable. In 2005 it was announced that an astronomical object (AB Pictoris b, abbreviated AB Pic b) had been imaged in 2003 and 2004 close to and apparently in orbit around the star. Its mass suggests that it is at the borderline between being a brown dwarf or a planet. In 2003 and 2004, an object (now catalogued as AB Pictoris b) was observed close to the star by a team of astronomers at the European Southern Observatory. Since it had common proper motion with AB Pictoris, it was concluded that it was physically close to the star. Its spectral type was estimated as between L0V and L3V. Using evolutionary models, its mass was estimated as from 13 to 14 Jupiter masses. However, because modelling such young objects is difficult, this estimate is very uncertain; some models give masses as low as 11 Jupiter masses or as high as 70 Jupiter masses. Temperature estimates range from 1600 K to
    6.00
    1 votes
    212
    Alpha Ophiuchi

    Alpha Ophiuchi

    • Category: Star
    Alpha Ophiuchi (α Oph, α Ophiuchi) is the brightest star in the constellation Ophiuchus. It has the traditional name Ras Alhague, often condensed to Rasalhague. Alpha Ophiuchi is a binary star system with an orbital period of about 8.62 years. The orbital parameters were only poorly known until 2011 when observations using adaptive optics produced a better orbital fit, allowing the individual masses of the two components to be determined. The primary component, Alpha Ophiuchi A, has a mass of about 2.4 times the mass of the Sun, while the secondary, Alpha Ophiuchi B, has 0.85 solar masses. Estimates of the mass of the primary by other means range from a low of 1.92 to 2.10 solar masses, up to 2.84 or even 4.8 solar masses. The mass of the secondary suggests that it has a stellar classification in the range K5V to K7V, which indicates it is a main sequence star that is still generating energy by the thermonuclear fusion of hydrogen at its core. The pair reached periastron passage, or closest approach, around April 19, 2012, when they had an angular separation of 50 milliarcseconds. This star system has a combined apparent magnitude of +2.08 and is located at a distance of about 48.6
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    1 votes
    213
    Alpha Pavonis

    Alpha Pavonis

    • Category: Star
    Alpha Pavonis (α Pav) is a star in the southern constellation Pavo, near the shared border with the Telescopium constellation. It is also known by the name Peacock, which was assigned by Her Majesty's Nautical Almanac Office in the late 1930s during the creation of the Air Almanac, a navigational almanac for the Royal Air Force. Of the fifty-seven stars included in the new almanac, two had no classical names: Epsilon Carinae and Alpha Pavonis. The RAF insisted that all of the stars must have names, so new names were invented. Alpha Pavonis was named "Peacock" ('pavo' is Latin for 'peacock') whilst Epsilon Carinae was called "Avior". At an apparent magnitude of 1.94, this is the brightest star in Pavo. Based upon parallax measurements, this star is about 179 light-years (55 parsecs) distant from the Earth. It has an estimated six times the Sun's mass and 5–6 times the Sun's radius, but 2,200 times the luminosity of the Sun. However, Tetzlaff et al (2011) suggest a much higher mass of 9 times the mass of the Sun. The effective temperature of the photosphere is 18,000 K, which gives the star a blue-white hue. A stellar classification of B2 IV suggests it is a subgiant star that has
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    1 votes
    214
    Epsilon Carinae

    Epsilon Carinae

    • Category: Star
    Epsilon Carinae (ε Car, ε Carinae) is a star in the southern constellation of Carina. It is also known by the name Avior. At apparent magnitude +1.86 it is one of the brightest stars in the night sky, but is not visible from the northern hemisphere. Epsilon Carinae is a double star located roughly 560–660 light-years (170–200 parsecs) away from the Earth. Measurements during the Hipparcos mission give the pair an angular separation of 0.46 arcseconds with a difference in magnitude of 2.0. At their estimated distance, this angle is equivalent to a physical separation of around 4 Astronomical Units. This pair may form an eclipsing binary system with a period of 785 days (2.15 years), resulting in a magnitude change of 0.12 during each eclipse. The primary component has an apparent visual magnitude of 2.2, which by itself would still make it the third brightest star in the constellation. It is an evolved giant star with a stellar classification of K0 III. However, examination of the ultraviolet flux from this star suggests it may instead be of spectral type K7. The fainter secondary companion has an apparent visual magnitude of 4.1, which, if it were a solitary star, would be bright
    6.00
    1 votes
    215
    HD 187123

    HD 187123

    • Category: Star
    HD 187123 is an 8th magnitude G-type main sequence star located approximately 156 light-years away in the constellation of Cygnus. Like our Sun, it is a yellow dwarf (spectral type G5V). Being at a distance of about 160 light-years it is not visible to the unaided eye. However, it should be easy target with binoculars or small telescope. In 1998 the California and Carnegie Planet Search team, after following a suggestion by Kevin Apps, a Briton who at the time was an undergraduate student found a possible planet orbiting the star. There were also indications of another, more distant body orbiting the star and this claim was published in 2006. This planet was confirmed in 2009.
    6.00
    1 votes
    216
    Iota Horologii

    Iota Horologii

    • Category: Star
    Iota Horologii (ι Hor, ι Horologii) is a solar twin, yellow dwarf star approximately 56 light-years away in the constellation of Horologium (the Pendulum Clock). The star is classified as a G0Vp yellow dwarf (it has previously been classified as G3 and a subgiant [IV]). It has a mass and radius larger than the Sun, and is about 50% more luminous. As of 1998, a single extrasolar planet is known orbiting Iota Horologii. Because the planet orbits in a near Earth orbit, Iota Horologii was ranked 69th in the list of candidates for NASA's planned Terrestrial Planet Finder mission. In 2000, a dust disc was announced around the star, but this was later determined to be an instrumental artifact. Since Iota Horologii is in the minor constellation of Horologium and is quite dim in the sky, it has not been given a traditional name. It lies roughly between the stars Eta Horologii and R Horologii (though it is not close to them in real space). In its current position, Iota Horologii is closest to the star Chi Eridani (a yellow subgiant), approximately 7 light-years away. The closest planetary systems to Iota Horologii are HD 10647 (a yellow dwarf), approximately 9 light-years away, and Epsilon
    6.00
    1 votes
    217
    Nu Cassiopeiae

    Nu Cassiopeiae

    • Category: Star
    Nu Cassiopeiae (ν Cas, ν Cassiopeiae) is a star in the constellation Cassiopeia. ν Cassiopeiae is a blue-white B-type giant with an apparent magnitude of +4.90. It is approximately 390 light years from Earth.
    6.00
    1 votes
    218
    Xi Scorpii

    Xi Scorpii

    • Category: Star
    Xi Scorpii (ξ Sco, ξ Scorpii) is a star system in the constellation Scorpius. It was also 51 Lib. The Xi Scorpii system consists of at least five stars in two groups separated by 4.67 arcminutes (or 0.08°) on the sky, corresponding to a distance of at least 8000 astronomical units (AU). The brighter group contains Xi Scorpii A, B, and C. A and B are both yellow-white F-type stars. A is a slightly brighter and warmer magnitude +4.8 subgiant, while B is a magnitude +5.1 main sequence dwarf. They are separated by 0.76 arcseconds, or at least 21 AU, roughly a Sun–Uranus distance, and orbit around a common centre once every 46 years. The magnitude +7.6 Xi Scorpii C orbits this pair at ten times the distance, having a separation of 7.6 arcseconds. The second group contains Xi Scorpii D and E. Both D and E are K-type stars, which are separated by 11.5 arcseconds, more than 320 AU. Xi Scorpii also possesses a sixth component, the 11th magnitude Xi Scorpii F, located 81 arcseconds from D. It is not known to be gravitationally bound to the other five components. Xi Scorpii was a latter designation of 51 Librae.
    6.00
    1 votes
    219
    Gamma Draconis

    Gamma Draconis

    • Category: Star
    Gamma Draconis (γ Dra, γ Draconis) is the Bayer designation for a star in the northern constellation of Draco. It has the traditional name Etamin or Eltanin and the Flamsteed designation 33 Draconis. Despite its gamma designation, it is actually the brightest star in Draco at magnitude 2.4, outshining Rastaban (Beta Draconis) by nearly half a magnitude. Its proximity to the zenith point directly overhead of London has earned it the name "Zenith Star." As for other places, it is relatively easy to locate in the night sky. If one finds Vega, Eltanin is the red star just north-northwest of it. Eltanin lies around 154.3 light-years (47.3 parsecs) away, as determined by parallax measurements from the Hipparcos astrometry satellite. In 1728, while unsuccessfully attempting to measure the parallax of this star, James Bradley discovered the aberration of light resulting from the movement of the Earth. Bradley's discovery confirmed Copernicus' theory that the Earth revolved around the Sun. Gamma Draconis is an evolved giant star with a stellar classification of K5 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It
    5.00
    2 votes
    220
    Gamma Orionis

    Gamma Orionis

    • Category: Star
    Bellatrix, also known by its Bayer designation Gamma Orionis (γ Ori, γ Orionis), is the third brightest star in the constellation Orion. A second-magnitude star, it is the twenty-seventh brightest star in the night sky. The name Bellatrix is Latin for female warrior. In the Alfonsine tables, it was also called the Amazon Star, a loose translation of the Arabic name Al Najīd, the Conqueror. It forms the left shoulder of Orion the Hunter. Bellatrix is one of the four navigational stars in Orion that are used for celestial navigation. The Chinese name for the star is 参宿五 ("The Fifth of the Three Stars"). This is a massive star with about 8.4 times the Sun's mass. It has an estimated age of approximately 20 million years; long enough for a star of this mass to consume the hydrogen at its core and begin to evolve away from the main sequence into a giant star. The effective temperature of the outer envelope of this star is 22,000 K, which is considerably hotter than the 5,778 K on the Sun. This high temperature gives this star the blue-white hue that occurs with B-type stars. The measured angular diameter of this star, after correction for limb darkening, is 0.72 ± 0.04 mas. At an
    5.00
    2 votes
    221
    Gamma2 Caeli

    Gamma2 Caeli

    • Category: Star
    Gamma Caeli (γ Cae, γ Caeli) is a binary star in the constellation Caelum. It is approximately 334 light years from Earth. The primary component, γ Caeli A, is a yellow-white F-type giant with a mean apparent magnitude of +6.32. It is classified as a Delta Scuti type variable star and its brightness varies from magnitude +6.28 to +6.39 with a period of 3.25 hours. The companion star, γ Caeli B, has an apparent magnitude of +9.6 and is located 0.886 arcseconds from the primary and spectral type F2IV/V.
    4.50
    2 votes
    222
    Alpha Centauri

    Alpha Centauri

    • Category: Star
    Alpha Centauri (α Centauri, α Cen; also known as Rigel Kent /ˈraɪdʒəl ˈkɛnt/—see names) is the brightest star in the southern constellation of Centaurus. Although it appears to the unaided eye as a single object, Alpha Centauri is actually a binary star system (designated Alpha Centauri AB or α Cen AB) whose combined visual magnitude of –0.27 would qualify it as the third-brightest single star in the night sky after the –1.46 magnitude Sirius and the –0.72 magnitude Canopus. Its individual component stars are named Alpha Centauri A (α Cen A), with 110% of the mass and 151.9% the luminosity of the Sun, and Alpha Centauri B (α Cen B), at 90.7% of the Sun's mass and 50.0% of its luminosity. During the pairs' 79.91-year orbit about a common center, the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun. They are 1.34 parsecs or 4.37 light years from the Sun. A third star, known as Proxima Centauri, Proxima or Alpha Centauri C (α Cen C), is probably gravitationally associated with Alpha Centauri AB. Proxima is at the slightly smaller distance of 1.29 parsecs or 4.24 light years from the Sun, making it the closest star to the Sun,
    5.00
    1 votes
    223
    Antares

    Antares

    • Category: Star
    Antares (α Scorpii, α Sco, Alpha Scorpii) is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky. (It is sometimes listed as 15th brightest, if the two brighter components of the Capella quadruple star system are counted as one star.) Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic. It is the brightest star in the constellation Scorpius, and is often referred to as "the heart of the scorpion". Antares is a slow variable star with an average magnitude of +1.09. Antares is a supergiant star with a stellar classification of M1.5Iab-b. It has a radius of approximately 883 times that of the Sun; if it were placed in the center of our solar system, its outer surface would lie between the orbits of Mars and Jupiter. Based upon parallax measurements, Antares is approximately 550 light-years (170 parsecs) from the Earth. Its visual luminosity is about 10,000 times that of the Sun, but because the star radiates a considerable part of its energy in the infrared part of the spectrum, the bolometric luminosity equals roughly 65,000 times that of the Sun. The mass of the star is calculated to be 15
    5.00
    1 votes
    224
    Delta Apodis

    Delta Apodis

    • Category: Star
    Delta Apodis (δ Aps, δ Apodis) is the Bayer designation for a double star in the southern constellation of Apus. The brighter star, δ¹ Apodis, is a M-type red giant with a mean apparent magnitude of +4.68. It is classified as an irregular variable star and its brightness varies from magnitude +4.66 to +4.87. At an angular separation of 102.9 arcseconds is δ² Apodis, an orange K-type giant with an apparent magnitude of +5.27. Hipparcos data report the distance to δ¹ Apodis to be approximately 760 light years, while δ² Apodis is found to be around 610 light years from Earth. They may form a common proper motion pair. In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of δ Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ Octantis, η Apodis, α Apodis and ε Apodis. Consequently, δ Apodis itself is known as 異雀六 (Yì Què liù, English: the Sixth Star of Exotic Bird.)
    5.00
    1 votes
    225
    Delta Capricorni

    Delta Capricorni

    • Category: Star
    Delta Capricorni (δ Cap, δ Capricorni), also traditionally named Deneb Algedi and Scheddi, is a binary star system approximately 39 light-years away in the constellation of Capricornus (the Sea Goat). The primary star in the system is a white giant star and the combined light of its members makes it the brightest "single" star within the constellation. Delta Capricorni is an eclipsing binary star system similar to Algol, with an orbital period of 1.022768 days and an inclination close to the line of sight from the Earth. The peak apparent visual magnitude of the pair is 2.81. During an eclipse of the primary, this magnitude drops by 0.24. When the primary is eclipsing the secondary, the magnitude decreases by 0.09. The primary component, Delta Capricorni A, has an overall stellar classification of A7m III, indicating that it is a giant star that has exhausted the supply of hydrogen at its core. More specifically, this is a chemically-peculiar Am star with a spectral type of kA5hF0mF2 III under the revised MK system. This notation indicates that the K-line matches the temperature of an A5 star, the hydrogen spectral type matches an F0 star, and the metallic absorption lines match an
    5.00
    1 votes
    226
    KW Sagitarii

    KW Sagitarii

    • Category: Star
    KW Sagittarii is a red supergiant, located approximately 10,000 light-years away from our Sun in the direction of the constellation Sagittarius. Its diameter is 1460 solar diameters, making it one of the largest known stars. Its bolometric luminosity is 360,000 times the Sun's.
    5.00
    1 votes
    227
    GQ Lupi

    GQ Lupi

    • Category: Star
    GQ Lupi is a T Tauri variable star approximately 500 light-years away in the constellation of Lupus. The star is young and has about 70% of the Sun's mass. In 2005, Ralph Neuhäuser and his colleagues reported a substellar object, GQ Lupi b, orbiting the star. Along with 2M1207b, this was one of the first extrasolar planet candidates to be directly imaged. The image was made with the VLT telescope at Paranal Observatory, Chile, on June 25, 2004. Depending on its mass and the definition of a planet, GQ Lupi b may or may not be considered a planet. As of 2006, the International Astronomical Union Working Group on Extrasolar Planets described GQ Lupi b as a "possible planetary-mass companion to a young star."
    4.00
    2 votes
    228
    Xi Persei

    Xi Persei

    • Category: Star
    Xi Persei (ξ Per) is a star in the constellation Perseus. It has the traditional name Menkib (Menchib, Menkhib, Arabic for "shoulder" [of the Pleiades]). Menkib has an apparent magnitude of +4.042 and is classified as a blue giant (spectral class O7.5III). It is approximately 1800 light years from Earth. Its apparent luminosity is 13,500 times that of the Sun. If we include the ultraviolet light that emanates from Menkib, however, its total (bolometric) luminosity increases to 330,000 times that of the Sun. The star has a mass of some 40 solar masses and a surface temperature of 37,000 kelvins, making it one of the hottest stars that can be seen with the naked eye.
    4.00
    2 votes
    229
    79 Ceti

    79 Ceti

    • Category: Star
    79 Ceti (also known as HD 16141) is a yellow subgiant star approximately 127 light-years away in the constellation Cetus. It has stopped hydrogen fusion in its core, this implies an age much higher than our Sun's 4.5 billion years. Eventually the outer layers of the star will expand and cool and the star will become a red giant. Currently 79 Ceti has a luminosity twice that of the Sun. As of 2000, an extrasolar planet, designated 79 Ceti b, is known to orbit 79 Ceti.
    4.00
    1 votes
    230
    Canopus

    Canopus

    • Category: Star
    Canopus (/kəˈnoʊpəs/; α Car, α Carinae, Alpha Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53. Canopus is a supergiant of spectral type F. Canopus is essentially white when seen with the naked eye (although F-type stars are sometimes listed as "yellowish-white"). It is located in the far southern sky, at a declination of −52° 42' (2000) and a right ascension of 06h24.0m. One of the least famous of the brightest stars, Canopus was not visible to the Ancient Greeks and Romans; it was, however, visible to the Ancient Egyptians. It is also referred to by its Arabic name: سهيل (Suhayl), given by Islamic scientists in the 7th Century CE. In the southern hemisphere, Canopus and Sirius are both visible high in the sky simultaneously, and reach the meridian just 21 minutes apart. It is a circumpolar star when seen from points that have latitude south of 37°18' south; for example, Victoria and Tasmania, Australia; Auckland and south of it, New Zealand; Bahía Blanca, Argentina; and Valdivia, Chile and south of
    4.00
    1 votes
    231
    Denebola

    Denebola

    • Category: Star
    Denebola (β Leo, β Leonis, Beta Leonis) is the second brightest star in the zodiac constellation of Leo. It is an A-type main sequence star with 75% more mass than the Sun and twelve times the Sun's luminosity. Based on parallax measurements from the Hipparcos astrometry satellite, the star is at a distance of about 36 light-years (11 parsecs) from Earth. Its apparent visual magnitude is 2.14, making it readily visible to the naked eye. Denebola is a Delta Scuti type variable star, meaning its luminosity varies very slightly over a period of a few hours. Its name is shortened from Deneb Alased, from the Arabic phrase ذنب الاسد ðanab al-asad "tail of the lion", as it represents the lion's tail—the star's position in the Leo constellation. Deneb in Cygnus has a similar name origin. In the Alphonsine Tables it was recorded as Denebalezeth. On R. A. Proctor's 1871 star chart of the northern hemisphere it was designated Deneb Aleet. To ancient Chinese astronomers, it formed part of the five-star Woo Ti Tsi 五帝座一: the Seat of the Twelve Emperors. In astrology, Denebola was believed to portend misfortune and disgrace. In Johann Bayer's Uranometria, published in 1603, the star was
    4.00
    1 votes
    232
    Mars

    Mars

    • Category: Planet
    • Locations: Olympus Mons
    Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. Named after the Roman god of war, it is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the highest known mountain within the Solar System, and of Valles Marineris, one of the largest canyons. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian trojan asteroid. Until the first successful flyby of Mars occurred in 1965 by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark
    4.00
    1 votes
    233
    Alpha Cancri

    Alpha Cancri

    • Category: Star
    Alpha Cancri (α Cnc, α Cancri) is a star system in the constellation Cancer. It has the traditional name Acubens (Açubens). Acubens is a fourth-magnitude star with an apparent magnitude of 4.20, making it barely visible to the naked eye under good lighting conditions. Nevertheless, it is 23 times more luminous than the Sun. Its stellar classification is A5m. The Hipparcos mission estimated the distance of Acubens to be roughly 53 parsecs from Earth, or approximately 174 light years away. Since it is near the ecliptic, it can be occulted by the Moon and very rarely by planets. The primary component, α Cancri A, is a white A-type main sequence dwarf with an apparent magnitude of +4.26. Its companion, α Cancri B, is an eleventh magnitude star. In the year 1836, its position angle was observed at 325 degrees with a separation from the main star α Cancri A of 11.3 arcseconds. From studying its light curve during occultation, it is thought that α Cancri A may itself be a close binary, consisting of two stars with similar brightness and a separation of 0.1 arcseconds. USS Acubens (AKS-5) was a United States navy ship
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    234
    Alpha Coronae Borealis

    Alpha Coronae Borealis

    • Category: Star
    Alpha Coronae Borealis (α CrB, α Coronae Borealis) is a binary star in the constellation Corona Borealis. It is located about 75 light years from the Solar System. The primary component is a white main sequence star that has a stellar classification of A0V and 2.6 times the mass of the Sun. Estimates of the star's radius range from 2.89 to 3.04 times the radius of the Sun. An excess of infrared radiation at 24 μm and 70 μm has been detected about the primary star by the IRAS. This suggests the presence of a large disc of dust and material around Alphecca, prompting speculation of a planetary or proto-planetary system similar to that currently assumed around Vega. The secondary component is a yellow main sequence star with an estimated stellar class of G5, 0.92 times the Sun's mass and 0.90 times the Sun's radius. The X-ray luminosity of this star is 6 × 10 erg s, which is 30 times greater than the peak activity level of the Sun. This higher activity level is expected for a young star of this class. The corona has a temperature of about 5 MK, which is much hotter than the Sun's corona. The upper limit of 14 km/s for the equatorial rotation velocity is equivalent to a rotation period
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    235
    Alpha Pegasi

    Alpha Pegasi

    • Category: Star
    Alpha Pegasi (α Peg, α Pegasi) is the third brightest star in the constellation Pegasus and one of the four stars in the asterism known as the Great Square of Pegasus. It has the traditional name Marko (or MT), which comes from an Arabic word مركب markab, "the saddle of the horse", or is mistranscription of Mankib comes from an Arabic phrase منكب الفرس Mankib al-Faras, "(the Star of) the Shoulder (of the Constellation) of the Horse" for β Pegasi. Marko aka MT has a stellar classification of B9 III, indicating that it is a B-type giant star that has exhausted the hydrogen at its core and has evolved beyond the main sequence. It is rotating rapidly, with a projected rotational velocity of 125 km/s giving a lower bound on the azimuthal velocity along the star's equator. The effective temperature of the photosphere is nearly 10,000 K and the star has expanded to nearly five times the radius of the Sun.
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    236
    Beta Cassiopeiae

    Beta Cassiopeiae

    • Category: Star
    Beta Cassiopeiae (β Cas, β Cassiopeiae) is a Delta Scuti variable star in the constellation Cassiopeia. It is a subgiant or giant star belonging to the spectral class F2, with a mean apparent magnitude of +2.27 and absolute magnitude of +1.16. It has the traditional name Caph, from the Arabic word كف kaf, "palm" (i.e. reaching from the Pleiades), also known as Al Sanām al Nākah. Another Arabic name is al-Kaff al-Khadib. With a mean apparent magnitude (V-band) of +2.27, it is one of the five stars which make up the 'W' of Cassiopeia, adjacent to the just brighter Schedar (Alpha Cassiopeiae). SN 1572, traditionally known as Tycho's Star, appeared about 5 degrees to the northwest of Caph in 1572. As a star in the deep northern hemisphere of the sky, Beta Cassiopeiae is prominent to viewers in the northern hemisphere but not often seen by those in the southern hemisphere. The constellation of Cassiopeia does not rise above the horizon to viewers in Tasmania, and only low if one were in Cairns. β Cassiopeiae is a yellow-white hued subgiant or giant of stellar class F2III-IV, with a surface temperature of 6,700 Kelvin. More than three times the size of and 28 times brighter than the sun,
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    237
    Epsilon Boötis

    Epsilon Boötis

    • Category: Star
    Epsilon Boötis (ε Boo, ε Boötis) is a double star in the northern constellation of Boötes. It has the traditional names Izar and Pulcherrima. The star system can be viewed with the unaided eye at night, but resolving the pair with a small telescope is challenging; an aperture of 76 mm (3.0 in) or greater is required. Epsilon Boötis consists of a pair of stars with an angular separation of 2.852 ± 0.014 arcseconds at a position angle of 342.°9 ± 0.°3. The brighter component (A) has an apparent visual magnitude of 2.37, making it readily visible to the naked eye at night. The fainter component (B) is at magnitude 5.12, which by itself would also be visible to the naked eye. Parallax measurements from the Hipparcos astrometry satellite put the system at a distance of about 203 light-years (62 parsecs) from the Earth. This means the pair has a projected separation of 185 Astronomical Units and they orbit each other with a period of at least 1,000 years. The brighter member has a stellar classification of K0 II-III, which means it is a fairly late-stage star well into its stellar evolution, having already exhausted its supply of hydrogen fuel at the core. With more than four times the
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    238
    Eta Leonis

    Eta Leonis

    • Category: Star
    Eta Leonis (η Leo, η Leonis) is a fourth-magnitude star in the constellation Leo. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Eta Leonis is a white supergiant with the stellar classification A0Ib. Though its apparent magnitude is 3.51, making it a relatively dim star to the naked eye, it is 5,600 times more luminous than the Sun, with an absolute magnitude of -5.60. The Hipparcos astrometric data has estimated the distance of Eta Leonis to be roughly 700 parsecs from Earth, or 2,000 light years away. There is evidence suggesting that Eta Leonis is part of a binary star system.
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    239
    Gamma Geminorum

    Gamma Geminorum

    • Category: Star
    Gamma Geminorum (γ Gem, γ Geminorum) is the second brightest star in the constellation Gemini. It has the traditional names Alhena and Almeisan. This star has an apparent visual magnitude of 1.9, making it easily visible to the naked eye even in urban regions. Based upon parallax measurements with the Hipparcos satellite, it is located at a distance of roughly 109 light-years (33 parsecs) from Earth. Alhena is an evolving star that is exhausting the supply of hydrogen at its core and has entered the subgiant stage. The spectrum matches a stellar classification of A1 IV. Compared to the Sun it has 2.8 times the mass and 3.3 times the radius. It is radiating around 123 times the luminosity of the Sun from its outer envelope at an effective temperature of 9,260 K. This gives it a white hue typical of an A-class star. This is a spectroscopic binary system with a period of 12.6 years (4,614.51 days) in a highly eccentric Keplerian orbit. The term Alhena is derived from the Arabic الهنعه Al Han'ah, "the brand" (on the neck of the camel), whilst the alternate name Almeisan is from the Arabic المیسان Al Maisan, "the shining one." Al Hanʽah was the name of star association consisting this
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    240
    Iota Apodis

    Iota Apodis

    • Category: Star
    Iota Apodis (ι Aps, ι Apodis) is the Bayer designation for a binary star system in the southern circumpolar constellation of Apus. It is a faint target at an apparent visual magnitude of 5.41, but still visible to the naked eye from suitably dark skies. The distance to this star can be roughly gauged from parallax measurements, yielding an estimate of 1,300 light-years (400 parsecs) with a 20% margin of error. Both stars are B-type main sequence stars, which indicates they shine with a blue-white hue. The brighter component has a stellar classification of B9 V and an apparent magnitude 5.90, while the second member is a B9.5 V star with a magnitude of 6.46. The pair have an angular separation of 0.091 arcseconds with a preliminary estimated orbital period of 51.441 years. In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of ι Apodis, ζ Apodis, β Apodis, γ Apodis, δ Octantis, δ Apodis, η Apodis, α Apodis and ε Apodis. Consequently, ι Apodis itself is known as 異雀二 (Yì Què èr, English: the Second Star of Exotic Bird.)
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    241
    Jupiter

    Jupiter

    • Category: Planet
    • Locations: Great Red Spot
    Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets. The planet was known by astronomers of ancient times, and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.) Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other gas giants, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it
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    242
    Lambda Andromedae

    Lambda Andromedae

    • Category: Star
    Lambda Andromedae (λ And, λ Andromedae) is the Bayer designation for a binary star in the northern constellation of Andromeda. At an estimated distance of approximately 86.1 light-years (26.4 parsecs) from Earth, it has an apparent visual magnitude of +3.8. This is bright enough to be seen with the naked eye. Lambda Andromedae is a single-lined spectroscopic binary with an orbital period of 20.5212 days. The spectrum of the primary matches a stellar classification of G8 III-IV, suggesting that it is an evolved star that lies part way between the subgiant and giant stages. The mass of this star is similar to the Sun, but it has expanded to around seven times the Sun's radius. It is radiating over 23 times the luminosity of the Sun from its outer envelope at an effective temperature of 4,800 K, giving it the characteristic yellow hue of a G-type star. This is an RS Canum Venaticorum variable and its brightness varies by 0.225 magnitudes, reaching a maximum of 3.70, with a period of 54.2 days. Such variability is theorized to occur because of tidal friction, which results in chromospheric activity. However, the orbit of this system is nearly circular, so the cause of this system's
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    Lambda Aquarii

    Lambda Aquarii

    • Category: Star
    Lambda Aquarii (λ Aqr, λ Aquarii) is the Bayer designation for a star in the equatorial constellation of Aquarius. It has the obscure traditional names Hydor and Ekkhysis, from the ancient Greek ὕδωρ "water" and ἔκχυσις "outpouring". The apparent visual magnitude of this star is 3.722, which is bright enough to be visible with the naked eye. It is roughly 390 light-years (120 pc) from Earth. In Chinese, 壘壁陣 (Lěi Bì Zhèn), meaning Line of Ramparts, refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, λ Aquarii itself is known as 壘壁陣七 (Lěi Bì Zhèn qī, English: the Seventh Star of Line of Ramparts.) Lambda Aquarii is a red giant star with a stellar classification of M2.5 III. It is a semiregular variable star star with pulsation periods of 24.5, 32.0, and 49.5 days. This star is on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen.
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    LHS 292

    LHS 292

    • Category: Star
    LHS 292 is a red dwarf star in the constellation Sextans. This star is far too faint to be seen with the unaided eye and requires a large amateur telescope to be seen visually. It lies relatively close to our Sun at a distance of about 14.8 light years. It is a flare star, which means it can suddenly increase in brightness for short periods of time. It has the space velocity components [U, V, W] = [28, −16, −14] km/s.
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    Mercury

    Mercury

    • Category: Planet
    • Locations: Antoniadi Dorsum
    Mercury is the innermost planet in the Solar System. It is also the smallest, and its orbit is the most eccentric (that is, the least perfectly circular) of the eight planets. It orbits the Sun once in about 88 Earth days, completing three rotations about its axis for every two orbits. The planet is named after the Roman god Mercury, the messenger to the gods. Mercury's surface is heavily cratered and similar in appearance to Earth's Moon, indicating that it has been geologically inactive for billions of years. Due to its near lack of an atmosphere to retain heat, Mercury's surface experiences the steepest temperature gradient of all the planets, ranging from a very cold 100 K at night to a very hot 700 K during the day. Mercury's axis has the smallest tilt of any of the Solar System's planets, meaning that there are no seasons on its surface. Mercury and Venus can each make appearances in Earth's sky both as a morning star and an evening star (because they are closer to the Sun than the Earth), and at times Mercury can technically be regarded as a very bright object when viewed from Earth; however, its proximity in the sky to the Sun makes it more difficult to see than
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    Mu Cassiopeiae

    Mu Cassiopeiae

    • Category: Star
    Mu Cassiopeiae (μ Cas, μ Cassiopeiae) is a binary star system in the constellation Cassiopeia. This system shares the name Marfak with Theta Cassiopeiae, and the name was from Al Marfik or Al Mirfaq (المرفق), meaning "the elbow". In 1961 the close binary nature of this system was discovered by Nicholas E. Wagman at the Allegheny Observatory. Since then the orbital elements of the two stars have been fairly well established. The two stars are separated by a semimajor axis of 7.61 AUs with distance range of 3.3-11.9 AUs. In 1966, the individual components were first resolved by the American astronomer Peter A. Wehinger using the 84-inch reflector at the Kitt Peak National Observatory, allowing an initial estimate of separate masses. Compared to other nearby stars, this pair are moving at a relatively high velocity of 167 km/s through the Milky Way galaxy. They are low metal, Population II stars that are thought to have formed before the galactic disk first appeared. This star will be in constellation Perseus around 5200 AD.
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    OGLE-2005-BLG-169L

    OGLE-2005-BLG-169L

    • Category: Star
    OGLE-2005-BLG-169L is a dim and distant magnitude 20 galactic bulge star located about 2,700 parsecs away in the constellation Sagittarius. If it is a main sequence star, then it is most likely a red dwarf with about half of the mass of the Sun. Other possibilities are a white dwarf star, or (less likely) a neutron star or black hole. In 2006, an Uranus-mass extrasolar planet was detected by gravitational microlensing around this star.
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    Rigel

    Rigel

    • Category: Star
    Rigel (β Ori, β Orionis, Beta Orionis) is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18. The star as seen from earth is actually a triple star system, with the primary star (Rigel A) a blue-white supergiant of absolute magnitude –7.84 and around 117,000 times as luminous as our sun. An Alpha Cygni variable, it pulsates periodically. Visible in small telescopes, Rigel B is itself a spectroscopic binary system, consisting of two main sequence blue-white stars of spectral type B9. Although Rigel has the Bayer designation "beta", it is almost always brighter than Alpha Orionis (Betelgeuse). Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Spectroscopic estimates of Rigel's distance place its distance between 700 and 900 light-years (210 and 280 pc), while Hipparcos's measurement of its parallax gives a distance of 860 light-years (260 pc), with a margin of error of about 9%. It is a blue supergiant, at about 18 solar masses, shining with approximately 117,000 times the luminosity of the Sun. The interferometer-measured angular diameter of this
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    VV Cephei

    VV Cephei

    • Category: Star
    VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, approximately 5,000 light years from Earth. A red supergiant fills the system's Roche lobe when closest to its companion blue star, the latter appearing to be on the main sequence. Matter flows from the red supergiant onto the blue companion for at least part of the orbit and the hot star is obscured by a large disk of material. The red supergiant primary, known as VV Cephei A, is currently recognised as one of the largest stars in the galaxy, with an estimated solar radius between 1,050 and 1,900. Although VV Cephei is an extremely large star showing high mass loss and having some emissions lines, the spectral luminosity class and absolute magnitude do not qualify it as a hypergiant. It should be possible to calculate the masses of eclipsing binary stars with some accuracy, but in this case mass loss, changes in the orbital parameters, a disk obscuring the hot secondary, and doubt about the distance of the system have led to wildly varying estimates. Calculations before the most recent primary and secondary eclipses had started to settle on masses of around 20 for both
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    Wolf 359

    Wolf 359

    • Category: Star
    Wolf 359 is a red dwarf star that is located in the constellation Leo, near the ecliptic. At a distance of approximately 7.8 light years from the Earth, it has an apparent magnitude of 13.5 and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to the Solar System; only the Alpha Centauri system (including Proxima Centauri) and Barnard's Star are known to be closer. Its proximity to Earth has led to its mention in several works of fiction. Wolf 359 is one of the faintest and lowest-mass stars known. At the light-emitting layer called the photosphere, it has a temperature of about 2,800 K, which is low enough for chemical compounds to form and survive. The absorption lines of compounds such as water and titanium(II) oxide have been observed in the spectrum. The surface has a magnetic field that is stronger than the average magnetic field on the Sun. As a result of magnetic activity caused by convection, Wolf 359 is a flare star that can undergo sudden increases in luminosity for several minutes. These flares emit strong bursts of X-ray and gamma ray radiation that have been observed by space telescopes. Wolf 359 is a relatively young star with an age of
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