A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an possibly the largest component tentatively named as dark matter.
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Messier 89 (M89 for short, also known as NGC 4552) is an elliptical galaxy in the constellation Virgo. It was discovered by Charles Messier on March 18, 1781. M89 is a member of the Virgo Cluster of galaxies.
Current observations indicate that M89 may be nearly perfectly spherical in shape. This is unusual, since all other known elliptic galaxies are relatively elongated ellipsoids. However, it is possible that the galaxy is oriented in such a way that it appears spherical to an observer on Earth but is in fact elliptical.
The galaxy also features a surrounding structure of gas and dust extending up to 150,000 light-years from the galaxy and jets of heated particles that extend 100,000 light-years outwards. This indicates that it may have once been an active quasar or radio galaxy.
M89 also has a large population of globular clusters. A 2006 survey estimates that there are 2,000 ± 700 globulars within 25′ of M89, compared to the estimated 150-200 thought to surround the Milky Way.
NGC 3109 is a small spiral or irregular galaxy around 4.2 Mly away in the direction of the constellation of Hydra. It is the most prominent member of a Local Group subgroup. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy, Antlia Dwarf. It was discovered by John Herschel on March 24, 1835 while he was in South Africa.
NGC 3109 is classified as a Magellanic type irregular galaxy, but it may in fact be a small spiral galaxy. If it is a spiral galaxy, it would be the smallest in the Local Group. NGC 3109 has a mass of about 2.3×10 times the mass of the Sun, of which 20% is in the form of neutral hydrogen. It is oriented edge-on from our point of view, and may contain a disk and a halo. The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars. NGC 3109 does not appear to possess a galactic nucleus.
From measurements of the neutral atomic hydrogen in the galaxy, it has been found that the disk of NGC 3109 is warped. The warp has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago.
Leo A ( also known as Leo III ) is an irregular galaxy that is part of the Local Group. It lies 2.25 million light-years from Earth. This galaxy was discovered by Fritz Zwicky in 1942. The estimated mass of this galaxy is (8.0 ± 2.7) × 10 solar masses, with at least 80% consisting of an unknown dark matter. It is one of the most isolated galaxies in the local group and shows no indications of an interaction or merger for several billion years. The presence of RR Lyrae variables shows that the galaxy has an old stellar population that is up to 10 billion years in age.
The neutral hydrogen in this galaxy occupies in a volume similar to its optical extent, and is distributed in a squashed, uneven ring. The galaxy is not rotating and the hydrogen is moving about in random clumps. The proportion of elements with higher atomic numbers than helium is only about 1-2% of the ratio in the Sun. This indicates a much lower rate of stellar evolution than in the Milky Way galaxy. The Leo A galaxy shows sign of increased star formation some time within the last billion years, although the current level is low. There are four H II regions powered by short-lived, O-class stars.
Abell 3266 is a galaxy cluster in the southern sky. It is part of the Horologium-Reticulum supercluster. The galaxy cluster is one of the largest in the southern sky, and one of the largest mass concentrations in the nearby universe.
The Department of Physics at the University of Maryland, Baltimore County discovered that a large mass of gas is hurtling through the cluster at a speed of 750 km/s. The mass is billions of solar masses, approximately three (3) million light years in diameter and is the largest of its kind so far discovered (June 2006).
NGC 4656/57 is a galaxy located in the constellation Canes Venatici and is sometimes informally called the Hockey Stick Galaxies or the Crowbar Galaxy. The galaxy is a member of the NGC 4631 Group. A Luminous Blue Variable in "super-outburst" was discovered in NGC 4656/57 by Doug Rich on March 21, 2005.
NGC 5253 is an irregular galaxy in the constellation Centaurus. It was discovered by John Frederick William Herschel on 15 March 1787.
NGC 5253 is located within the M83 Subgroup of the Centaurus A/M83 Group, a relatively nearby group of galaxies that includes the radio galaxy Centaurus A and the spiral galaxy M83 (the Southern Pinwheel Galaxy).
NGC 5253 is considered a dwarf starburst galaxy. Supernova 1972E, the brightest supernova visible from Earth (visual magnitude of 8.5) in the 20th century after 1987A, occurred in this galaxy.
UGC 8091 (also known as GR 8) is a gas-rich dwarf irregular galaxy. In 1995, Tolstoy et al. estimated its distance to be (with the Hipparcos correction of 1997 applied) ~7.9 Million light-years from Earth. There is still open question regarding if it is a member of the Local Group. It was discovered at the Lick Observatory using the 20-inch astrograph in either 1946, 1947, or 1951.
Arp 299 (also known as IC 694 and NGC 3690) is a pair of colliding galaxies approximately 134 million light-years away in the constellation Ursa Major. Both of the galaxies involved in the collision are barred irregular galaxies.
It is not completely clear which object is historically called IC 694. According to some sources, the small appendage more than an arcminute northwest of the main pair is actually IC 694, not the primary (eastern) companion.
The interaction of the two galaxies in Arp 299 produced young powerful starburst regions similar to those seen in II Zw 96. Six supernovae have been detected in Arp 299: SN 1992bu, SN 1993G, SN 1998T, SN 1999D were observed in NGC 3690 while SN 1990al and SN 2005U were observed in IC 694.
NGC 5713 is a peculiar, asymmetric galaxy in the constellation Virgo. Although classified as a spiral galaxy by most galaxy catalogs, NGC 5713 galaxy is very different from most normal spiral galaxies. While most spiral galaxies either have either two well-defined spiral arms or a filamentary spiral-like structure, this spiral galaxy has only one visible spiral arm in its disk. Gravitational interactions with the nearby spiral galaxy NGC 5719 may be responsible for producing the disturbed, asymmetric structure including the single spiral arm.
NGC 5713 is at the center of a small group of spiral galaxies that also includes NGC 5691 and NGC 5705 along with NGC 5719.
Compared to many other nearby spiral galaxies, NGC 5713 appears to be a site of relatively intense star formation activity. The boost in star formation in NGC 5713 may be linked to the gravitational interactions with NGC 5719. The interactions are expected to disturb the orbits of gas clouds in NGC 5713, thus causing the clouds to collide with each other. The collisions cause the clouds to collapse and form new stars, hence leading to the increased star formation seen in NGC 5713.
NGC 5258 is a spiral galaxy located in the constellation Virgo. The galaxy is notably interacting with the spiral galaxy NGC 5257. The two galaxies are listed together as Arp 240 in the Atlas of Peculiar Galaxies. Both galaxies are distorted by the gravitational interaction, and both are connected by a tidal bridge, as can be seen in images of these galaxies.
NGC 2500 is a barred spiral galaxy in the constellation Cancer which was discovered by William Herschel in 1788. Much like the local group in which our own Milky Way galaxy is situated, NGC 2500 is part of NGC 2841 group of galaxies which also includes NGC 2541, NGC 2537 and NGC 2552. It has a H II nucleus.
Ursa Major I Dwarf (UMa I dSph) is a dwarf spheroidal galaxy orbiting the Milky Way galaxy. The discovery by Beth Willman et al. was announced in 2005.
Being a small dwarf galaxy, it measures only a few thousand light-years in diameter. As of 2006, it is the third least luminous galaxy known (discounting possible dark galaxies such as VIRGOHI21 in the Virgo cluster of galaxies), after the Boötes Dwarf (absolute magnitude -5.7) and the more recently discovered Ursa Major II Dwarf (absolute magnitude -3.8). The absolute magnitude of the galaxy is estimated to be only -6.75, meaning that it is less luminous than some stars, like Deneb in the Milky Way. It is comparable in luminosity to Rigel. It has been described as similar to the Sextans Dwarf Galaxy. Both galaxies are ancient and metal-deficient.
It estimated to be located at a distance of about 330,000 light-years (100 Kpc) from the Earth. That is about twice the distance to the Large Magellanic Cloud; the largest and most luminous satellite galaxy of the Milky Way.
There was another object called Ursa Major Dwarf, discovered by Edwin Hubble in 1949. It was designated as Palomar 4. Due to its peculiar look, it was temporarily
NGC 2903 is a barred spiral galaxy about 30 million light-years away in the constellation Leo. It was discovered by William Herschel who cataloged it on November 16, 1784. NGC 2905 is a bright star cloud within this galaxy.
NGC 1097 (also known as Caldwell 67) is a barred spiral galaxy about 45 million light-years away in the constellation Fornax. As of 2006, three supernovae (SN 1992bd, SN 1999eu, and SN 2003B) have been observed in NGC 1097.
NGC 1097 is also a Seyfert galaxy. Deep photographs by Wolstencroft & Zealey (1975), Arp (1976), and Lorre (1978) revealed four narrow optical jets that appear to emanate from the nucleus. Arp interpreted these as manifestations of the (currently weak) active nucleus. Subsequent analysis of the brightest jet's radio-to-X-ray spectral energy distribution by Carter, Allen & Malin (1984), Wehrle, Keel, & Jones (1997) and Higdon & Wallin (2003) were able to rule out synchrotron and thermal free-free emission. The optical jets are in fact composed of stars. The failure to detect atomic hydrogen gas in the jets (under the assumption that they were an example of tidal tails) using deep 21 cm HI imaging with the Very Large Array radio telescope and numerical simulations led to the current interpretation that the jets are actually the shattered remains of a cannibalized dwarf galaxy (Higdon & Wallin 2003).
Like most massive galaxies, NGC 1097 has a supermassive black
NGC 4450 is a spiral galaxy in the constellation Coma Berenices.
NGC 4450 is a member of the Virgo Cluster that, like Messier 90, shows smooth, nearly featureless spiral arms, with few star formation regions and little neutral hydrogen compared to other similar spiral galaxies, something that justifies its classification as an anemic galaxy.
Measurements with the help of the Hubble Space Telescope show the center of this galaxy has a supermassive black hole
NGC 5257 is a spiral galaxy located in the constellation Virgo. The galaxy is notably interacting with the spiral galaxy NGC 5258. The two galaxies are listed together as Arp 240 in the Atlas of Peculiar Galaxies. Both galaxies are distorted by the gravitational interaction, and both are connected by a tidal bridge, as can be seen in images of these galaxies.
3C75 (aka 3C 75) is a binary black hole system in the Abell 400 cluster of galaxies. It has four radio jets (two from each accreting black hole). It is travelling at 1200 kilometers per second through the cluster plasma, causing the jets to be swept back. The binary supermassive black holes are themselves contained in the dumbbell shaped galaxy NGC 1128. 3C 75 may be X-ray source 2A 0252+060 (1H 0253+058, XRS 02522+060).
Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparable to those of Triangulum Galaxy.
Dwingeloo 1 has two smaller satellite galaxies: Dwingeloo 2 and MB 3 and is a member of the IC 342/Maffei Group of galaxies.
The Dwingeloo 1 galaxy was discovered in 1994 by the Dwingeloo Obscured Galaxy Survey (DOGS), which searched for neutral hydrogen (HI) radio emissions at the wavelength of 21 cm from objects in the Zone of Avoidance. In this zone gas and dust in the disk of the Milky Way galaxy block the light from the galaxies lying behind it.
The galaxy was, however, first noted as an unremarkable feature on Palomar Sky Survey plates earlier in the same year, but was not recognized as such. It was also independently discovered a few weeks later by another team of astronomers working with Effelsberg 100-m Radio Telescope.
After the discovery Dwingeloo 1 was classified as a barred spiral galaxy. The distance to it was found to be approximately 3 Mpc(Megaparsecs). In its overall size and mass the galaxy is
Messier 100 (also known as NGC 4321) is an example of a grand design spiral galaxy located within the southern part of constellation Coma Berenices. It is one of the brightest and largest galaxies in the Virgo cluster, approximately 55 million light-years distant from Earth and has a diameter of 160,000 light years. It was discovered by Pierre Méchain on March 15, 1781 and was subsequently entered in Messier’s catalogue of nebulae and star clusters after Charles Messier made observations of his own on April 13, 1781. The galaxy was one of the first spirals discovered, and was listed as 1 of 14 spiral nebulae by Lord William Parsons of Rosse in 1850. Two satellite galaxies named NGC 4323 -connected with M100 by a bridge of luminous matter- and NGC 4328 are present within this galaxy.
After the discovery of M100 by Méchain, Charles Messier made observations of the galaxy depicting it as a nebula without a star. He pointed out that it was difficult to recognize the nebula because of its faintness. William Herschel was able to identify a bright cluster of stars within the nebula during observations he did before John Herschel expanded the findings in 1833. With the advent of better
NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy about 2.08 million light-years away in the constellation Cassiopeia. It is a member of the Local group, and is a satellite galaxy of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is classified as a type 2 Seyfert galaxy.
At least two techniques have been used to measure distances to NGC 185. The surface brightness fluctuations distance measurement technique estimates distances to galaxies based on the graininess of their appearance. The distance measured to NGC 185 using this technique is 2.08 ± 0.15 Mly (640 ± 50 kpc). However, NGC 185 is close
The Pegasus Dwarf Irregular Galaxy (also known as Peg DIG or the Pegasus Dwarf) is an irregular galaxy and a dwarf galaxy in the direction of the constellation Pegasus. It was discovered by A.G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the Andromeda Galaxy in the Local Group.
In 1975 Tully & Fisher determined that it was part of the Local Group. The metallicity and the related distance estimate has been subject to discussions in the scientific literature, with varying results, however, recently, by use of the tip of the red giant branch, a distance within 10% error was achieved in 2000 and then improved to 3% in 2005.
This galaxy is presumed to be the primary location of the science fiction television series Stargate: Atlantis. While it's mentioned the show takes place in "the Pegasus galaxy" it has not explicitly stated if it is the Irregular or Spheroidal. However, when the Pegasus galaxy has been seen from the Midway station an irregular galaxy is shown. Also, in the discussion regarding the new McKay-Carter Intergalactic Gate Bridge, General Hank Landry states that the distance between the Pegasus and Milky Way galaxies is "three million light-years," suggesting
Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. Once believed to be a member of the Local Group of galaxies, it is now known to belong to its own group, the IC 342/Maffei Group. It was named after Paolo Maffei, who discovered it and the neighboring Maffei 2 in 1967 via their infrared emissions.
Maffei 1 is a slightly flattened core type elliptical galaxy. It has a boxy shape and is made mainly of old metal-rich stars. It has a tiny blue nucleus in which stars continue to form. Like all large ellipticals it contains a significant population of globular clusters. Maffei 1 is situated at an estimated distance of 3–4 Mpc from the Milky Way. It may be the closest giant elliptical galaxy.
Maffei 1 lies in the Zone of Avoidance and is heavily obscured by the Milky Way's stars and dust. If it were not obscured, it would be one of the largest (about 3/4 the size of the full Moon) brightest and best-known galaxies in the sky. It can be observed visually, using a 30–35 cm or bigger telescope under a very dark sky.
The Italian astronomer Paolo Maffei (1926–2009) was one of the pioneers of infrared astronomy. In the 1950s and 60s, in order to obtain high quality images of
Messier 109 (also known as NGC 3992) is a barred spiral galaxy approximately 83.5 ± 24 million light-years away in the constellation Ursa Major. M109 can be seen southeast of the star Phecda (γ UMa).
Messier 109 was discovered by Pierre Méchain in 1781. In 1783 Charles Messier catalogued NGC 3992 as his 109th object.
Between the 1920s through the 1950s, it was considered that Messier objects over 103 were not official, but in later years the additions became more widely accepted. David H. Levy mentions the modern 110 object catalog while Sir Patrick Moore gave the original to 104 but has M105-M109 listed as an addendum. By the late 1970s all 110 objects are commonly used among astronomers as they still are today.
In March 1956, supernova 1956A was observed in M109. SN 1956A was a type Ia supernova in the southeast part of the galaxy, glowing at magnitude 12.8 to 12.3 at its maximum. SN 1956A has been the only supernova observed in M109 since its discovery.
M109 has three satellite galaxies (UGC 6923, UGC 6940 and UGC 6969) and possibly might have more. Detailed hydrogen line observations have been obtained from M109 and its satellites. M109's H I distribution is regular with a low
NGC 404 is a small lenticular galaxy located about 10 million light years away in the constellation Andromeda. It was discovered by William Herschel in 1784, and is visible through small telescopes. NGC 404 lies just beyond the Local Group but does not appear gravitationally bound to it. It is notable for being within 7 arc-minutes of second magnitude star Mirach, making it a difficult target to observe or photograph and granting it the nickname "Mirach's Ghost".
NGC 404 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms.
At least two techniques have been used to measure distances to NGC 404. The infrared surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to NGC 404 using this technique in 2003 is 9.9 ± 0.5 Mly (3.03 ± 0.15 Mpc).
However, NGC 404 is close enough that red supergiants can be imaged as individual stars. The light from these stars and knowledge of how they should compare to nearby stars within the Milky Way galaxy allows for direct
NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs.
NGC 5195 was discovered by Pierre Méchain on March 20, 1781.
NGC 5195 and the Whirlpool Galaxy comprise one of the most noted interacting galaxy pairs in astronomy. The two galaxies are listed in the Atlas of Peculiar Galaxies as one of several prominent examples of a spiral galaxy with a companion galaxy. The system was also the subject of very early theoretical investigations into galaxy interactions. The two galaxies are connected by a dust-rich tidal bridge. The dust in this tidal bridge can be seen silhouetted against the center of NGC 5195. This demonstrates that NGC 5195 appears to lie behind the Whirlpool Galaxy. The encounter has significantly enhanced the spiral structure of M51.
As a consequence of the gravitational interaction with the Whirlpool Galaxy, NGC 5195 is highly distorted. Classification of its morphology is difficult, as it is sometimes
NGC 1300 is a barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way. It may be part of the Eridanus Cluster. It was discovered by John Frederick William Herschel in 1835.
The image on the right was taken with Hubble Space Telescope during September 2004. It is a composite using four filters: Blue (with a center wavelength of 435 nm), Visual (555 nm), Infrared (814 nm) and Hydrogen-alpha (658 nm). The image's resolution, a myriad of fine details, some of which have never before been seen, is seen throughout the galaxy's arms, disk, bulge, and nucleus. Blue and red supergiant stars, star clusters, and star-forming regions are well resolved across the spiral arms, and dust lanes trace out fine structures in the disk and bar. Numerous more distant galaxies are visible in the background, and are seen even through the densest regions of NGC 1300.
In the core of the larger spiral structure of NGC 1300, the nucleus shows its own extraordinary and distinct "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale
The Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/61) are a pair of interacting galaxies in the constellation Corvus. They are currently going through a phase of starburst. They were discovered by William Herschel in 1785. NGC 4038 is located at RA 12 01 53.0, Dec −18° 52′ 10″; and NGC 4039 at RA 12 01 53.6, Dec −18° 53′ 11″.
The Antennae are undergoing a galactic collision. Located in the NGC 4038 group with five other galaxies, these two galaxies are known as the 'Antennae' because the two long tails of stars, gas and dust thrown out of the galaxies as a result of the collision resemble the antennae of an insect. The nuclei of the two galaxies are joining to become one giant galaxy. Most galaxies probably undergo at least one significant collision in their lifetimes. This is likely the future of our Milky Way when it collides with the Andromeda Galaxy. Two supernovae have been discovered in the galaxies: SN 2004GT and SN 2007sr.
A recent study finds that these interacting galaxies are closer to the Milky Way than previously thought—at 45 million light-years instead of 65 million light-years.
About 1.2 billion years ago, the Antennae were two separate galaxies.
Canes Venatici I or CVn I is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey. It is one the most distant satellites of the Milky Way as of 2011 together with Leo I and Leo II. The galaxy is located at the distance of about 220 kpc from the Sun and moves away from the Sun with the velocity of about 31 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical (ratio of axes ~ 2.5:1) shape with the half-light radius of about 550 pc.
CVn I is a relatively faint satellite of the Milky Way—its integrated luminosity is about 230,000 times that of the Sun (absolute visible magnitude of about −8.6). However, its mass is about 27 million solar masses, which means that galaxy's mass to light ratio is around 220. A high mass to light ratio implies that CVn I is dominated by the dark matter.
The stellar population of CVn I consists mainly of old stars formed more than 10 billion years ago. The metallicity of these old stars is also very low at [Fe/H] ≈ −2.08 ± 0.02, which means that they contain 110 times less heavy elements than the Sun. There are also about 60 RR
NGC 3949 is an unbarred spiral galaxy in the constellation Ursa Major. It is believed to be approximately 50 million light-years away from the earth.
The type II supernova SN 2000db is the only supernova that has been observed within NGC 3949.
NGC 3949 is a member of the M109 Group, a group of galaxies located in the constellation Ursa Major that may contain over 50 galaxies. The brightest galaxy in the group is the spiral galaxy M109.
Arp 220 is the result of a collision between two galaxies which are now in the process of merging. Located 250 million light-years away in the constellation Serpens, it is the 220th object in Halton Arp's Atlas of Peculiar Galaxies.
Arp 220 is the closest Ultraluminous Infrared Galaxy (ULIRG) to Earth. Its energy output was discovered by IRAS to be dominated by the far-infrared part of the spectrum. It is often regarded as the prototypical ULIRG and has been the subject of much study as a result. Most of its energy output is thought to be the result of a massive burst of star formation, or starburst, probably triggered by the merging of two smaller galaxies. Recent (2002 and 1997) HST observations of Arp 220, taken in visible light with the ACS, and in infrared light with NICMOS, revealed more than 200 huge star clusters in the central part of the galaxy. The most massive of these clusters contains enough material to equal about 10 million suns. X-ray observations by the Chandra and XMM-Newton satellites have shown that Arp 220 probably includes an active galactic nucleus (AGN) at its core, which raises interesting questions about the link between galaxy mergers and AGN, since it
Messier 106 (also known as NGC 4258) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. It is also a Seyfert II galaxy, which means that due to x-rays and unusual emission lines detected, it is suspected that part of the galaxy is falling into a supermassive black hole in the center. NGC 4217 is a possible companion galaxy of Messier 106.
M106 has a water vapor megamaser (the equivalent of a laser operating in microwave instead of light and on a galactic scale) that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas. Water masers are useful to observe nuclear accretion disks in active galaxies. The water masers in M106 enabled the first case of a direct measurement of the distance to a galaxy and thereby providing an independent anchor for the cosmic distance ladder. M 106 has a slightly warped, thin, almost edge-on Keplerian disk which is on a subparsec scale. It surrounds a central area with mass 4 × 10M⊙.
NGC 1275 (also known as Perseus A or Caldwell 24) is a type 1.5 Seyfert galaxy located around 237 million light-years away in the direction of the constellation Perseus. NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the centre of the large Perseus Cluster of galaxies.
NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it. The central cluster galaxy contains a massive network of spectral line emitting filaments, which appear to be being dragged out by rising bubbles of relativistic plasma generated by the central active galactic nucleus. Long gaseous filaments made up of threads of gas stretch out beyond the galaxy, into the multimillion-degree, X-ray–emitting gas that fills the cluster. The amount of gas contained in a typical thread is approximately one million times the mass of our own Sun. They are only 200 light-years wide, are often very straight,
Abell 2667 is a galaxy cluster. It is one of the most luminous galaxy clusters in the X-ray waveband known at redshift about 0.2.
This cluster is also a well-known gravitational lens.
On 2 March 2007, a team of astronomers reported the detection of comet galaxy in this cluster. This galaxy is being ripped apart by the cluster’s gravitational field and harsh environment. The finding sheds light on the mysterious process by which gas-rich spiral-shaped galaxies might evolve into gas-poor irregular- or elliptical-shaped galaxies over billions of years.
The Pegasus Dwarf Spheroidal (also known as Andromeda VI or Peg dSph for short) is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus. The Pegasus Dwarf is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31).
Pegasus Dwarf Spheroidal is a galaxy with mainly metal-poor stellar populations. Its metallicity is [Fe/H] ≃ −1.3. It is located at the right ascension 23h51m46.30s and declination +24d34m57.0s in the equatorial coordinate system (epoch J2000.0), and in a distance of 820 ± 20 kpc from Earth and a distance of 294 ± 8 kpc from the Andromeda Galaxy.
Pegasus Dwarf Spheroidal was discovered in 1999 by various authors on the Second Palomar Sky Survey (POSS-II) films.
The Fornax Dwarf Spheroidal is an elliptical dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. He discovered it while he was in South Africa on photographic plates taken by a 24 inch reflecting telescope at Boyden Observatory, shortly after he discovered the Sculptor Dwarf galaxy.
The galaxy is a satellite of the Milky Way and contains six globular clusters; the largest, NGC 1049, was discovered before the galaxy itself. The galaxy is also receding from the Milky Way at 53 km/s. It mostly contains population II stars.
Using the Hubble Space Telescope, in 1999, Buonanno et al. derived a color-magnitude diagram for Fornax 4, a globular cluster within this galaxy. Unlike the globular clusters Fornax 1, 2, 3, and 5, which have horizontal branches across a wide range of colors and include RR Lyrae variables, Fornax 4 is found to have only red in its horizontal branch. Fornax 4 is also ~3 Gyr younger than the other globular clusters. Buonanno et al. note that the color-magnitude diagram of Fornax 4 has a strong similarity to "young" galactic globular Ruprecht 106. This leads to two open questions: Why do dwarf spheroidals allow the formation of
Messier 84 (also known as M84 or NGC 4374) is a lenticular galaxy in the constellation Virgo. M84 is situated in the heavily populated inner core of the Virgo Cluster of galaxies.
Radio observations and Hubble Space Telescope images of M84 have revealed two jets of matter shooting out from the galaxy's center as well as a disk of rapidly rotating gas and stars indicating the presence of a 1.5 ×10 M☉ supermassive black hole.
Charles Messier discovered Messier 84 on 18 March 1781 in a systematic search for "nebulous objects" in the night sky. The object is the 84th in the Messier Catalogue.
Two supernovae have been observed in M84: SN 1957 and SN 1991bg. Possibly, a third, SN 1980I is part of M84 or, alternatively, one of its neighboring galaxies, NGC 4387 and M86.
NGC 2537 is a blue compact dwarf galaxy in the constellation Lynx. This is also known as Bear's Paw Galaxy, Arp 6, and Mrk 86. It belongs to the iE class of Blue Compact Dwarf (BCD) classification, which is described as galactic spectra with an underlying smooth elliptical Low Surface Brightness component with a superimposed "knotted" star formation component (Gil de Paz et al., 2000, Page 378 Astron. Astrophys. Suppl. Ser. 145).
NGC 4618 is a distorted dwarf galaxy in the constellation Canes Venatici. The galaxy is formally classified as a Sm galaxy, which means that its structure vaguely resembles the structure of spiral galaxies. The galaxy is sometimes referred to as a Magellanic spiral because of its resemblance to the Magellanic clouds.
Unlike most spiral galaxies, NGC 4618 has a single spiral arm, which gives the galaxy an asymmetric appearance. This galaxy was included in the Atlas of Peculiar Galaxies as one of three examples of nearby galaxies with single spiral arms. Although NGC 4618 is labeled as peculiar, many similar galaxies have been identified.
It has been hypothesized that this galaxy's asymmetric structure may be the result of a gravitational interaction with NGC 4625. Such asymmetric structure is commonly seen among many interacting galaxies. However, observations of neutral hydrogen gas in NGC 4618 and NGC 4625 imply that only some of the gas outside the optical disks of NGC 4618 is affected by the gravitational interaction. This may indicate that NGC 4618's one-arm shape forms as the result of processes that are intrinsic to the galaxy itself.
As mentioned above, NGC 4618 is
Huchra's lens is the lensing galaxy of the Einstein Cross (Quasar 2237+30); it is also called ZW 2237+030 or QSO 2237+0305 G. It exhibits the phenomenon of gravitational lensing that was postulated by Albert Einstein when he realized that gravity would be able to bend light and thus could have lens-like effects. The galaxy is named for astronomer John Huchra.
NGC 4555 is a solitary elliptical galaxy about 40,000 parsecs (125,000 light-years) across. Observations by the Chandra X-ray Observatory have shown it to be surrounded by a halo of hot gas about 120,000 parsecs across. The hot gas has a temperature of around 10,000,000 kelvins. The galaxy is one of the few elliptical galaxies proven to have significant amounts of dark matter. Large amounts of dark matter are necessary to prevent the gas from escaping the galaxy; the visible mass clearly is not large enough to hold such an extensive gas halo. The dark matter halo is estimated to have 10 times the mass of the stars in the galaxy.
NGC 4555 is important because of its isolation. Most elliptical galaxies are found in the cores of groups and clusters of galaxies, and almost all those for which dark matter estimates are available are located in the centres of these larger systems. In these circumstances it impossible to know whether the dark matter is associated with the galaxy or the surrounding cluster. NGC 4555, as a field galaxy is not part of any group or cluster, and therefore provides strong evidence that dark matter can be associated with individual ellipticals.
Messier 65 (also known as NGC 3623) is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by Charles Messier in 1780. M65, M66, and NGC 3628 comprise the famous Leo Triplet, a small group of galaxies.
M65 was discovered by Charles Messier and included in his Messier Objects list. However, William Henry Smyth accidentally attributed the discovery to Pierre Méchain in his popular 19th century astronomical work A Cycle of Celestial Objects (stating "They [M65 and M66] were pointed out by Méchain to Messier in 1780"). This error was in turn picked up by Kenneth Glyn Jones in Messier's Nebulae and Star Clusters. This has since ramified into a number of other books by a variety of authors.
The galaxy is low in dust and gas, and there is little star formation in it, although there has been some relatively recently in the arms. The ratio of old stars to new stars is correspondingly quite high. In most wavelengths it is quite uninteresting, though there is a radio source visible in the NVSS, offset from the core by about two arc-minutes. The identity of the source is uncertain, as it has not been identified visually, or formally
MS 0735.6+7421 is a galaxy cluster.
The most powerful eruption since the big bang apparently has occurred there. Using data from the Chandra Space Telescope, scientists have deduced that an eruption has been occurring for the last 100 million years at the heart of the galaxy cluster, releasing as much energy over this time as hundreds of millions of gamma ray bursts. (The amount of energy released in a year is thus equivalent to several GRBs.) The remnants of the eruption are seen as two cavities on either side of a large central galaxy. If this outbust, with a total energy budget of more than 10 J, was caused by a black hole accretion event, it must have consumed nearly 600 million solar masses. Recent work done by Brian McNamara et al. (2008) point out the striking possibility that the outburst was not the result of an accretion event, but was instead powered by the rotation of the black hole. Moreover the scientists mentioned the possibility that the central black hole in MS 0735.6+7421 could be one of the biggest black holes inhabiting the visible universe. This speculation is supported by the fact that the central cD Galaxy inside MS 0735.6+7421 possess the largest break
NGC 4559 (also known as Caldwell 36) is a spiral galaxy in the constellation Coma Berenices. Distance estimates for NCG 4559 range from about 29 million light-years to 51 million light-years, averaging about 29 million light-years.
NGC 57 is an elliptical galaxy in the constellation Pisces.
On June 3, 2010, Koichi Itagaki detected a magnitude 17 supernova 17" west and 1" south of the center of NGC 57 at coordinates 00 15 29.70 +17 19 41.0.
NGC 7479 (also known as Caldwell 44) is a barred spiral galaxy about 105 million light-years away in the constellation Pegasus. It was discovered by William Herschel in 1784. Supernovae SN 1990U and SN2009jf occurred in NGC 7479. NGC 7479 is also recognized as a Seyfert galaxy undergoing starburst activity in the nucleus and the outer arms (Kohno, 2007). Polarization studies of this galaxy indicate that it recently underwent a minor merger and that it is unique in the radio continuum, with arms opening in a direction opposite to the optical arms (Laine, 2005).
The Sculptor Dwarf Galaxy (also called the Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the constellation Sculptor. It was discovered in 1937 by Harlow Shapley. The galaxy is located about 290,000 light-years away from the solar system. The Sculptor Dwarf contains only 4 percent of the carbon and other heavy elements in our own galaxy, the Milky Way, making it similar to primitive galaxies seen at the edge of the universe.
In 1999, Majewski et al. determined that the metallicity of Sculptor dwarf appears to be broken up into two distinct groups, one with [Fe/H] = -2.3 and the other with [Fe/H] = -1.5. Similar to many of the other Local Group galaxies, the older metal-poor segment appears more extended than the younger metal-rich segment.
Hoag's Object is a non-typical galaxy of the type known as a ring galaxy. The appearance of this object has interested amateur astronomers as much as its uncommon structure has fascinated professionals. The galaxy is named after Arthur Allen Hoag who discovered it in 1950 and identified it as either a planetary nebula or a peculiar galaxy with eight billion stars.
A nearly perfect ring of young hot blue stars circles the older yellow nucleus of this ring galaxy ~600 million light-years away in the constellation Serpens. The diameter of the 6″ (seconds of arc) inner core of the galaxy is about 17±0.7 kly (5.3±0.2 kpc) while the surrounding ring has an inner 28″ diameter of 75±3 kly (24.8±1.1 kpc) and an outer 45″ diameter of 121±4 kly (39.9±1.7 kpc), which is slightly larger than the Milky Way Galaxy. The gap separating the two stellar populations may contain some star clusters that are almost too faint to see. As rare as this type of galaxy is, another more distant currently unnamed ring galaxy can be seen through Hoag's Object, between the nucleus and the outer ring of the galaxy, at roughly the 12:05 position in the picture to the right.
Even though Hoag's Object was clearly
Messier 98 (also known as M98 or NGC 4192) is an intermediate spiral galaxy about 60 million light-years away in the constellation Coma Berenices. It was discovered by Pierre Méchain on 15 March 1781 along with M99 and M100 and was cataloged as a Messier object on 13 April 1781. Messier 98 has a blue shift and is approaching us at about 140 km per second.
Messier 98 is a member of the Virgo Cluster, which is a large, relatively nearby cluster of galaxies.
NGC 4236 (also known as Caldwell 3) is a barred spiral galaxy located in the constellation Draco.
NGC 4236 is a member of the M81 Group, a group of galaxies located at a distance of approximately 11.7 Mly (3.6 Mpc) from Earth. The group also contains the well-known spiral galaxy Messier 81 and the well-known starburst galaxy Messier 82.
NGC 3384 is a Elliptical galaxy in the constellation Leo. The Galaxy was discovered by Herschel in 1784. The high age of the stars in the central region of NGC 3384 was confirmed after analysis of their color. More than 80% were found to be Population II stars which are over a billion years old.
NGC 3384 is a member of the M96 Group, a group of galaxies in the constellation Leo that is sometimes referred to as the Leo I Group. This group also includes the Messier objects M95, M96, and M105. All of these objects are conspicuously close to each other in the sky.
NGC 2683 is an unbarred spiral galaxy discovered by William Herschel on February 5, 1788. It was nicknamed the "UFO Galaxy" by the Astronaut Memorial Planetarium and Observatory. It is viewed nearly edge-on from Earth's location in space and is located between 16 to 25 million light-years away. It is receding from Earth at 410 km/s (250 mi/s), and from the Galactic Center at 375 km/s (233 mi/s). The reddened light from the center of the galaxy appears yellowish due to the intervening gas and dust located within the outer arms of NGC 2683.
Media related to NGC 2683 at Wikimedia Commons
NGC 4631 (also known as the Whale Galaxy or Caldwell 32) is an edge-on spiral galaxy in the constellation Canes Venatici. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname. Because this nearby galaxy is seen edge-on from Earth, professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.
NGC 4631 contains a central starburst, which is a region of intense star formation. The strong star formation is evident in the emission from ionized hydrogen and interstellar dust heated by the stars formed in the starburst. The most massive stars that form in star formation regions only burn hydrogen gas through fusion for a short period of time, after which they explode as supernovae. So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This superwind can be seen in X-rays and in spectral line emission. The gas from this superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.
NGC 4631 has a nearby companion dwarf elliptical galaxy, NGC 4627. NGC 4627 and NGC 4631
The Phoenix Dwarf is a dwarf galaxy and an irregular galaxy that was discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster. It is currently 1.44 Mly away from Earth. Its name comes from the fact that it is part of the Phoenix constellation.
The Phoenix dwarf has an inner part of young stars running in an east-west direction and an outer part of mainly old stars that runs north-south. The central region's rate of star formation seems to have been relatively constant across time (Martínez-Delgado et al. 1999). In 1999, St-Germain et al. discovered a H I region of about 10 M☉ just to the west of Phoenix. Its radial velocity is -23 km/s and may be physically associated with Phoenix if it is found to have a similar radial velocity.
NGC 7320 is a spiral galaxy in the Stephan's Quintet. However, it is not an actual member of the galaxy group, but a much closer line-of-sight galaxy at a distance of about 40 million light years. Other galaxies of Stephan's Quintet are some 300 million ly distant.
The Carina Dwarf Spheroidal is a dwarf galaxy in the Carina constellation. It was discovered in 1977 with the UK Schmidt Telescope by Cannon et al. The Carina Dwarf is receding from the Milky Way at 230 km/s and is a satellite galaxy to the Milky Way. The galaxy may also be referred to as ESO 206-G20 or PGC 19441. It appears to have formed several billion years after the formation of the other satellite galaxies of the Milky Way as its older stars are younger than 7 billion years. This makes it a relatively youthful galaxy when compared to the Milky Way, which is estimated to have formed 13.6 billion years ago, or nearly as old as the Universe itself. It probably has a complex star formation history, with three possible distinct bursts of star formation. It is also being tidally disrupted by the Milky Way galaxy.
The Circinus Galaxy (ESO 97-G13) is a Seyfert Galaxy in the Circinus constellation. It is only 4 degrees below the Galactic plane, and 13 million light-years away. The galaxy is undergoing tumultuous changes, as rings of gas are being ejected from the galaxy. The outermost ring is 700 light-years from the center of the galaxy and the inner ring is 130 light-years out. The Circinus galaxy can be seen using a small telescope, however it was not noticed until 25 years ago because it was obscured by material from our own galaxy. The Circinus Galaxy is a Type II Seyfert galaxy and is one of the closest known active galaxies to the Milky Way, though it is probably slightly further away than Centaurus A.
Circinus Galaxy was a home for SN 1996cr, that has been identified over a decade after it exploded. The supernova was first singled out in 2001 as a bright, variable object in a Chandra image, but it was not confirmed as a supernova until years later.
Messier 49 (also known as M 49 or NGC 4472) is an elliptical galaxy located about 49 million light-years away in the equatorial constellation of Virgo. This galaxy was discovered by French astronomer Charles Messier on February 19, 1771. Messier 49 is positioned 4.1° west-southwest of the star Epsilon Virginis.
As an elliptical galaxy, Messier 49 has the physical form of a radio galaxy, but it only has the radio emission of a normal galaxy. From the detected radio emission, the core region is emitting roughly 10 erg of energy. The nucleus of this galaxy is emitting X-rays, suggests the likely presence of a supermassive black hole with an estimated mass of 5.65 × 10 solar masses, or 565 million times the mass of the Sun. X-ray emissions shows a structure to the north of Messier 49 that resembles a bow shock. To the southwest of the core, the luminous outline of the galaxy can be traced out to a distance of 260 kpc. The only supernova event observed within this galaxy is SN 1969Q, discovered in June 1969.
This galaxy has a large collection of globular clusters, estimated at about 5,900. However, this count is far exceeded by the 13,450 globular clusters orbiting the supergiant
NGC 3054 is an intermediate spiral galaxy in the constellation Hydra. It was discovered by Christian Heinrich Friedrich Peters in 1859. In January 2006, a supernova (SN 2006T) was obsered in NGC 3054. It is probably in the same galaxy group as NGC 2935.
NGC 5033 is an inclined spiral galaxy located in the constellation Canes Venatici. Distance estimates vary from between 38 to 60 million light years from the Milky Way Galaxy. The galaxy has a very bright nucleus and a relatively faint disk. Significant warping is visible in the southern half of the disk. The galaxy's relatively large angular size and relatively high surface brightness make it an object that can be viewed and imaged by amateur astronomers. The galaxy's location relatively near Earth and its active galactic nucleus make it a commonly studied object for professional astronomers.
NGC 5033 contains a Seyfert nucleus, a type of active galactic nucleus. Like many other active galactic nuclei, this galaxy's nucleus is thought to contain a supermassive black hole. The bright emission seen in visible light (as well as other wavebands) is partially produced by the hot gas in the environment around this black hole.
Integral field spectroscopic observations of the center of NGC 5033 indicate that the Seyfert nucleus is not located at the kinematic center of the galaxy (the point around which the stars in the galaxies rotate). This has been interpreted as evidence that this
NGC 7217 is an unbarred spiral galaxy in the constellation Pegasus.
NGC 7217 is a gas-poor system whose main features are the presence of several rings of stars concentric to its nucleus: three main ones -being the outermost one the most prominent and the one that features most of the gas and star formation of this galaxy-, plus several others inside the innermost one discovered with the help of the Hubble Space Telescope, a feature that suggests NGC 7217's central regions have suffered several starbursts, and a very large and massive spheroid that extends beyond its disk.
Other noteworthy features this galaxy has are the presence of a number of stars rotating in the opposite direction around the galaxy's center to most of them and two distinct stellar populations: one of intermediate age on its innermost regions and a younger, metal-poor on its outermost ones.
It has been suggested these features were caused by a merger with another galaxy and, in fact, computer simulations show that NGC 7217 could have been a large lenticular galaxy that merged with one or two smaller gas-rich ones of late Hubble type becoming the spiral galaxy we see today.; however right now this galaxy is
Messier 108 (also known as NGC 3556) is a barred spiral galaxy in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 or 1782. From the perspective of the Earth, this galaxy is seen almost edge-on.
This galaxy is an isolated member of the Ursa Major Cluster cluster of galaxies in the Virgo supercluster. It has a morphological classification of type SBbc in the de Vaucouleurs system, which means it is a barred spiral galaxy with somewhat loosely wound arms. The maximum angular size of the galaxy in the optical band is 11′.1 × 4′.6, and it is inclined 75° to the line of sight.
This galaxy has an estimated mass of 125 billion times the mass of the Sun and includes about 290 ± 80 globular clusters. Examination of the distribution of neutral hydrogen in this galaxy shows shells of expanding gas extending for several kiloparsecs, known as H1 supershells. These may be driven by bursts of star formation activity, resulting in supernovae explosions. Alternatively they may result from an infall of gas from outside the galaxy or by radio jets.
Observations with the Chandra X-ray Observatory have identified 83 X-ray sources, including a source located at the nucleus. The
NGC 1309 is a spiral galaxy located approximately 120 million light-years away in the constellation Eridanus. It is about 75,000 light-years across; about 3/4s the width of our own galaxy, the Milky Way. Its shape is classified as SA(s)bc, meaning that it has moderately wound spiral arms and no ring. Bright blue areas of star formation can be seen in the spiral arms, while the yellowish central nucleus contains older-population stars. NGC 1309 is one of over 200 members of the Eridanus Group of galaxies.
The image on the right is a composite of 25 hours of exposures taken by the Hubble Space Telescope (HST) during August and September 2005 using the B (blue: 435 nm), V (visual: 555 nm) and I (infrared: 814 nm) filters. The image is a square capturing 2.9 x 2.9 arcminutes of sky (roughly 100,000 light-years per side). Note: the smaller galaxies visible in the image are in the distant background; they are not satellites.
SN 2002fk was discovered jointly by Reiki Kushida of the Yatsugatake South Base Observatory, Nagano Prefecture, Japan; and Jun-jie Wang and Yu-Lei Qiu of the Beijing Astronomical Observatory on Sept. 17.719 UT. When it was discovered it was magnitude ~15.0; it was
NGC 6744 (also known as Caldwell 101) is an intermediate spiral galaxy about 30 million light-years away in the constellation Pavo. It is considered one of the most Milky Way-like spiral galaxies in our immediate vicinity, with flocculent (fluffy) arms and an elongated core. It also has at least one distorted companion galaxy (NGC 6744A) superficially similar to one of the Magellanic Clouds.
The Sagittarius Dwarf Irregular Galaxy or SagDIG is a dwarf galaxy in the constellation of Sagittarius. It lies about 3.4 million light-years away. SagDIG should not be confused with the Sagittarius Dwarf Elliptical Galaxy or SagDEG, a satellite galaxy of the Milky Way. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO (B) Atlas on June 13, 1977 using the ESO 1 meter Schmidt telescope.
The SagDIG is the most remote object from the barycenter thought to be a member of the Local Group. It is only slightly outside the zero-velocity surface of the Local Group.
SagDIG is a much more luminous galaxy than Aquarius Dwarf and it has been through a prolonged star formation (Momany et al. 2005). This has resulted in it containing a rich intermediate-age population of stars. Twenty-seven candidate carbon stars have been identified inside SagDIG. Analysis shows that the underlying stellar population of SagDIG is metal-poor (at least [Fe/H] ≤ −1.3). Further, the population is young, with the most likely average age between 4 and 8 Gyr for the dominant population.
Abell 1835 IR1916 (also known as Abell 1835, Galaxy Abell 1835, or Galaxy Abell 1835 IR1916) was a candidate for being the most distant galaxy ever observed. It was claimed to lie behind the galaxy cluster Abell 1835, in the Virgo constellation. It was discovered by French and Swiss astronomers of the European Southern Observatory, namely Roser Pelló, Johan Richard, Jean-François Le Borgne, Daniel Schaerer, and Jean-Paul Kneib. The astronomers used a near-infrared instrument on the Very Large Telescope to detect the galaxy; other observatories were then used to make an image of it possible. The Observatory, in conjunction with the Swiss National Science Foundation, the French Centre National de la Recherche Scientifique, and the journal Astronomy and Astrophysics, issued a press release on 1 March 2004 announcing the discovery. It was believed to be more distant than the galaxy lensed by Abell 2218.
Their analysis of J-band observations indicated that Abell 1835 IR1916 has a redshift factor of z~10.0, meaning that, according to the Big Bang Theory, it appears to us as it was about 13.2 billion years ago, only 500 million years after the Big Bang and very close to the first burst of
Messier 90 (also known as M90 and NGC 4569) is a spiral galaxy about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.
Messier 90 is a member of the Virgo Cluster. The galaxy is located approximately 1°.5 away from the subgroup centered on Messier 87. As a consequence of the galaxy's interaction with the intracluster medium in the Virgo Cluster, the galaxy has lost much of its interstellar medium. As a result of this process, which is referred to as ram-pressure stripping, the galaxy's interstellar medium and star formation regions appear severely truncated compared to similar galaxies outside the Virgo Cluster and there're even H II regions outside the galactic plane.
As stated above, the star formation in Messier 90 appears truncated. Consequently, the galaxy's spiral arms appear to be smooth and featureless, rather than knotted like galaxies with extended star formation., which justifies why this galaxy, along with NGC 4921 in the Coma Cluster has been classified as the prototype of an anemic galaxy. Some authors go even further and consider it's a passive spiral galaxy, similar to those found on galaxy clusters with high
NGC 3314 is a pair of overlapping spiral galaxies between 117 and 140 million light-years away in the constellation Hydra. This unique alignment gives astronomers the opportunity to measure the properties of interstellar dust in the face-on foreground galaxy (NGC3314a), which appear dark against the background galaxy (NGC 3314b). Unlike interacting galaxies, the two components of NGC3314 are physically unrelated.
While searching for overlapping galaxies in April 1999, two astronomers from the University of Alabama were the first to image the deep sky object in enough detail to tell that it was in fact two galaxies. In a March 2000 observation of the galaxies, a prominent green star-like object was seen in one of the arms. Astronomers theorized that it could have been a supernova, but the unique filtering properties of the foreground galaxy made it difficult to decide definitively.
NGC 6745 (also known as UGC 11391) is an irregular galaxy about 206 million light-years (63.5 mega-parsecs) away in the constellation Lyra. It is actually a triplet of galaxies in the process of colliding.
The three galaxies have been colliding for hundreds of millions of years. After passing through the larger galaxy (NGC 6745A), the smaller one (NGC 6745B) is now moving away. The larger galaxy was probably a spiral galaxy before the collision, but was damaged and now appears peculiar. It is unlikely that any stars in the two galaxies collided directly because of the vast distances between them. The gas, dust, and ambient magnetic fields of the galaxies, however, do interact directly in a collision. As a result of this interaction, the smaller galaxy has probably lost most of its interstellar medium to the larger one.
The age of NGC 6745 is estimated to be ~10 Myr.
Media related to NGC 6745 at Wikimedia Commons
Sextans B (also known as UGC 5373 and DDO 70) is an irregular galaxy that may be part of the Local Group, or lie just beyond it. Sextans B is 4.44 million light-years away from Earth and thus is one of most distant members of the Local Group, if it is indeed a member. It forms a pair with its neighbouring galaxy Sextans A. It is a type Ir IV-V galaxy according to the galaxy morphological classification scheme. Sextans B may also be gravitationally associated with the galaxies NGC 3109 and the Antlia Dwarf.
Sextans B has a uniform stellar population, but the interstellar medium in it may be inhomogeneous. Its mass is estimated to be about 2 × 10 times the mass of the Sun, of which 5.5 × 10 is in the form of atomic hydrogen. Star formation in the galaxy seems to have proceeded in distinct periods of low intensity, separated by shorter periods of no activity. The existence of Cepheid variables in the galaxy implies that Sextans B contains at least some young stars. The metallicity of Sextans B is rather low, with a value of approximately Z = 0.001. Sextans B is receding from the Milky Way with a speed of approximately 300 kilometres per second (190 mi/s), and probably lies just
IC 342 (also known as Caldwell 5) is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy, located about 7 million light years away is near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.
IC 342 is one of the brightest two galaxies in the IC 342/Maffei Group of galaxies, one of the galaxy groups that is closest to the Local Group. The galaxy was discovered by William Frederick Denning in 1895. Edwin Hubble first thought it to be in the Local Group, but later it was demonstrated that the galaxy is outside the Local Group.
In 1935, Harlow Shapely declared that this galaxy was the third largest galaxy by angular size then known, smaller only than the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33), being wider that the full moon. This does not take into account the visual size of the LMC or SMC.
It has a H II nucleus.
Leo II (or Leo B) is an dwarf spheroidal galaxy about 690,000 light-years away in the constellation Leo. As of October 2008 it is one of 24 known satellite galaxies of the Milky Way. As of 2007 Leo II is thought to have a core radius of 178 ± 13 pc and a tidal radius of 632 ± 32 pc. It was discovered in 1950 by Robert G. Harrington and Albert George Wilson, from the Mount Wilson and Palomar Observatories in California.
In 2007 a team of 15 scientists observed Leo II through the 8.2 meter Subaru optical-infrared telescope in Mauna Kea, Hawaii. Over 2 nights, 90 minutes of exposures were taken and 82,252 stars were detected down to a visible magnitude of 26. They found that Leo II consists of largely of metal-poor older stars, a sign that it has survived the galactic cannibalism under which massive galaxies (e.g., the Milky Way) consume smaller galaxies to attain their extensive size.
Observation at ESO estimates Leo II's mass to be (2.7 ± 0.5)×10 M⊙.
The Milky Way is the galaxy that contains the Earth. This name derives from its appearance as a dim "milky" glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars. The term "Milky Way" is a translation of the Classical Latin via lactea, from the Hellenistic Greek γαλαξίας κύκλος (pr. galaxías kýklos, "milky circle"). The Milky Way appears like a band because it is a disk-shaped structure being viewed from inside. The fact that this faint band of light is made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars. In the 1920s, observations by astronomer Edwin Hubble showed that the Milky Way is just one of many galaxies.
The Milky Way is a barred spiral galaxy 100,000–120,000 light-years in diameter containing 200–400 billion stars. It may contain at least as many planets, with an estimated 10 billion of those orbiting in the habitable zone of their parent stars. The Solar System is located within the disk, around two thirds of the way out from the Galactic Center, on the inner edge of a spiral-shaped concentration of gas and dust called the Orion–Cygnus Arm. The stars in the inner
NGC 1055 is an edge-on spiral galaxy located in the constellation Cetus that has a prominent nuclear bulge crossed by a wide, knotty, dark lane of dust and gas. The spiral arm structure appears to be elevated above the galaxy's plane and obscures the upper half of the bulge. Discovered on December 19, 1783 by William Herschel from his home in Slough England.
It is a binary system together with the bright spiral galaxy M77 (NGC 1068). These two are the largest galaxies of a small galaxy group that also includes NGC 1073, and five other small irregular galaxies.
NGC 1087, NGC 1090, and NGC 1094 appear close, but they simply appear in the field of view and are background galaxies.
Based on the published red shift, (Hubble Constant of 62 km/s per Mpc) a rough distance estimate for NGC 1055 is 52 million light-years, with a diameter of about 115,800 light-years. The separation between NGC 1055 and M77 is about 442,000 light-years.
NGC 1055 is a bright infrared and radio source, particularly in the wavelength for warm carbon monoxide. Astronomers believe that this results from unusually active star formation. It most likely has a transitional nucleus, however, there is a small chance
NGC 5866 (also called the Spindle Galaxy or Messier 102) is a relatively bright lenticular or spiral galaxy in the constellation Draco. NGC 5866 was probably discovered by Pierre Méchain or Charles Messier in 1781, and independently found by William Herschel in 1788.
One of the most outstanding features of NGC 5866 is the extended dust disk, which is seen exactly edge-on. This dust disk is highly unusual for a lenticular galaxy. The dust in most lenticular galaxies is generally found only near the nucleus and generally follows the light profile of the galaxies' bulges. This dust disk may contain a ring-like structure, although the shape of this structure is difficult to determine given the edge-on orientation of the galaxy. It is also possible that the galaxy is a spiral galaxy that was misclassified as a lenticular galaxy because of its edge-on orientation, in which case the dust disk would not be too unusual.
NGC 5866 is one of the brightest galaxies in the NGC 5866 Group, a small galaxy group that also includes the spiral galaxies NGC 5879 and NGC 5907. This group may actually be a subclump at the northwest end of a large, elongated structure that comprises the M51 Group and the
The Sagittarius Dwarf Elliptical Galaxy (Sag DEG) is an elliptical loop-shaped satellite galaxy of the Milky Way Galaxy. It consists of four globular clusters, the main cluster being discovered in 1994. Sag DEG is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit at a distance of about 50,000 light-years from the core of the Milky Way (about 1/3 the distance of the Large Magellanic Cloud). It should not be confused with the Sagittarius Dwarf Irregular Galaxy, or the Sag DIG, a small galaxy 3.4 million light-years distant.
Officially discovered in 1994, by Rodrigo Ibata, Mike Irwin, and Gerry Gilmore, Sag DEG was immediately recognized as being the nearest known neighbor to our Milky Way at the time. (Since 2003, the newly discovered Canis Major Dwarf Galaxy is considered the actual nearest neighbor). Although it is one of the closest companion galaxies to the Milky Way, the main parent cluster is on the opposite side of the galactic core from Earth, and consequently is very faint, although it covers a large area of the sky. Sag DEG appears to be an older galaxy, with little interstellar dust and composed
Sextans A (also known as UGCA 205), is a tiny dwarf irregular galaxy. It spans about 5000 light-years across, and is located within the Local Group of galaxies, which includes our Milky Way galaxy. At 4.3 million light-years away from Earth, Sextans A is one of most distant members of the Local Group, and is notable for its peculiar square shape. Massive short-lived stars exploded in supernovae that caused more star formation, triggering yet more supernovae, ultimately resulting in an expanding shell. Young blue stars now highlight areas and shell edges high in current star formation, which from the perspective of observers on Earth appears roughly square.
NGC 4881 is an elliptical galaxy about 352 million light-years away in the constellation Coma Berenices. It is a member of the Coma cluster of galaxies. NGC 4881 was discovered by Heinrich Louis d'Arrest in 1865.
In 1994, the Hubble Space Telescope took a look at the Coma cluster and NGC 4881.
NGC 7814 (also known as UGC 8 or Caldwell 43) is a spiral galaxy about 40 million light-years away in the constellation Pegasus. The galaxy is seen edge-on from Earth. It is sometimes referred to as "the little sombrero", a miniature version of Messier 104. The star field behind NGC 7814 is known for its density of faint, remote galaxies as can be seen in the image here – in the same vein as the Hubble Deep Field.
The Cassiopeia Dwarf (also known as Andromeda VII) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. The Cassiopeia Dwarf is part of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31).
The Cassiopeia Dwarf was found in 1998, together with the Pegasus Dwarf, by a team of astronomers (Karachentsev and Karachentseva) in Russia and the Ukraine. The Cassiopeia Dwarf and the Pegasus Dwarf are farther from M31 than its other known companion galaxies, yet still appear bound to it by gravity. Neither galaxy contains any young, massive stars or shows traces of recent star formation. Instead, both seem dominated by very old stars, with ages of up to 10 billion years.
Cygnus A (3C 405) is one of the most famous radio galaxies, and among the strongest radio sources in the sky. It was discovered by Grote Reber in 1939. In 1951, Cygnus A, along with Cassiopeia A, and Puppis A were the first "radio stars" identified with an optical source, of these, Cygnus A became the first radio galaxy; the other two being nebulae inside the Milky Way. In 1953 Roger Jennison and M K Das Gupta showed it to be a double source. Like all radio galaxies, it contains an active galactic nucleus.
Images of the galaxy in the radio portion of the electromagnetic spectrum show two jets protruding in opposite directions from the galaxy's center. These jets extend many times the width of the portion of the host galaxy which emits radiation at visible wavelengths. At the ends of the jets are two lobes with "hot spots" of more intense radiation at their edges. These hot spots are formed when material from the jets collides with the surrounding intergalactic medium.
Cygnus A appears in Carl Sagan's Contact as the result of beings actively creating a galaxy.
NGC 2535 is an unbarred spiral galaxy in the constellation Cancer that is interacting with NGC 2536. The two galaxies are listed together in the Atlas of Peculiar Galaxies as an example of a spiral galaxy with a high surface brightness companion.
NGC 4650A is a polar-ring lenticular galaxy located in the constellation Centaurus. It should not be confused with the spiral galaxy NGC 4650, which shares almost the same radial distance as NGC 4650A. The real distance between both galaxies is only about 6 times the optical radius of NGC 4650.
NGC 1042 is a spiral galaxy in the Constellation Cetus.
The galaxy appears near the spiral galaxy NGC 1035 in the sky, and both have similar redshifts. The two objects may therefore be physically associated with each other.
NGC 5090 and NGC 5091 are a set of galaxies approximately 150 million light-years away in the constellation Centaurus. They are in the process of colliding and merging with some evidence of tidal disruption of NGC 5091.
NGC 5090 is an elliptical galaxy while NGC 5091 is a spiral galaxy. The velocity of the nucleus of NGC 5091 has been measured as 3429 km/s, while NGC 5090 has a velocity of 3185 km/s. NGC 5090 is associated with a strong, double radio source (PKS 1318-43).
The Eyes Galaxies (NGC 4435-NGC 4438, also known as Arp 120) are a pair of galaxies about 52 million light-years away in the constellation Virgo.
NGC 4435 is a barred lenticular galaxy with a relatively young (age of 190 million years) stellar population on its central regions that has been discovered by the Spitzer Space Telescope and whose origin may be the interaction with NGC 4438. It also has a long tidal tail possibly caused by the interaction with the mentioned galaxy
NGC 4438 is the most curious interacting galaxy in the Virgo Cluster, due to the uncertainty surrounding the energy mechanism that heats the nuclear source; this energy mechanism may be a starburst region, or a Black Hole powered active galactic nucleus (AGN). Both of the hypotheses are still being investigated.
This galaxy shows a highly distorted disk with long tidal tails due to interactions with other galaxies, that explain why sources differ to classify it as a lenticular or spiral galaxy. It also shows signs of a past extended -but modest- starburst, a considerable deficience of neutral hydrogen as well as a displacement of the components of its interstellar medium -atomic hydrogen, molecular hydrogen,
Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is the prototype nearby starburst galaxy about 12 million light-years away in the constellation Ursa Major. The starburst galaxy is five times as bright as the whole Milky Way and one hundred times as bright as our galaxy's center.
In 2005, the Hubble Space Telescope revealed 197 young massive clusters in the starburst core. The average mass of these clusters is around 2×10 M⊙, hence the starburst core is a very energetic and high-density environment. Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy.
M82 was previously believed to be an irregular galaxy. However, in 2005, two symmetric spiral arms were discovered in the near-infrared (NIR) images of M82. The arms were detected by subtracting an axisymmetric exponential disk from the NIR images. These arms emanate from the ends of the NIR bar and can be followed for the length of 3 disc scales. Even though the arms were detected in the NIR images, they are bluer than the disk. Assuming that the northern part of M82 is nearer to us, which most literature assumes, the observed sense of rotation implies
NGC 5005 (also known as Caldwell 29) is an inclined spiral galaxy in the constellation Canes Venatici. The galaxy has a relatively bright nucleus and a bright disk that contains multiple dust lanes. The galaxy's high surface brightness makes it an object that is visible to amateur astronomers using large amateur telescopes.
Distance measurements for NGC 5005 vary from 13.7 megaparsecs (45 million light-years) to 34.6 megaparsecs (113 million light-years), averaging about 20 megaparsecs (65 million light-years).
NGC 5005 contains a low ionization nuclear emission region (LINER) nucleus. LINER nuclei contain weakly ionized gas. The power source for the LINER emission has been debated extensively, with some researchers suggesting that LINERs are powered by active galactic nuclei that contain supermassive black holes and other researchers suggesting that LINERs are powered by star formation activity.
X-ray observations of NGC 5005 have revealed that it contains a variable, point-like hard X-ray source in its nucleus. These results imply that NGC 5005 contains a supermassive black hole. The strong, variable X-ray emission is characteristic of the emission expected from the hot,
The Sombrero Galaxy (also known as M104 or NGC 4594) is an unbarred spiral galaxy in the constellation Virgo located 28 million light years from Earth. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy. But Spitzer found that halo around the Sombrero Galaxy is larger and more massive than previously thought, indicative of a giant elliptical galaxy. The galaxy has an apparent magnitude of +9.0, making it easily visible with amateur telescopes. The large bulge, the central supermassive black hole, and the dust lane all attract the attention of professional astronomers.
The Sombrero Galaxy was discovered in March 1767 by Pierre Méchain, who described the object in a May 1767 letter to J. Bernoulli that was later published in the Berliner Astronomisches Jahrbuch. Charles Messier made a hand-written note about this and five other objects (now collectively recognized as M104 - M109) to his personal list of objects now known as the Messier Catalogue, but it was
Messier 102 (also known as M102) is a galaxy listed in the Messier Catalogue that has not been identified unambiguously. Its original discoverer Pierre Méchain later said that it was a duplicate observation of Messier 101, but there are historical and observational reasons to believe that it could be NGC 5866, although other galaxies have been suggested as possible identities.
Since the publication of the Messier Catalogue, a number of galaxies have been identified by different historians, professional astronomers, and amateur astronomers as corresponding to M102.
Messier 101 (also known as the Pinwheel Galaxy or NGC 5457) is a face-on spiral galaxy in the constellation Ursa Major. In a letter written in 1783 to J. Bernoulli, Pierre Méchain (who had shared information about his discoveries with Messier) claimed that M102 was actually an accidental duplication of M101 in the catalog. This letter was later published twice: First in original French in the Memoirs of the Berlin Academy for 1782, and second in German translation and somewhat rearranged by Johann Elert Bode in the Berliner Astronomisches Jahrbuch for 1786.
NGC 5866 (one of two galaxies commonly called the Spindle Galaxy)
Messier 58 (also known as M58 and NGC 4579) is a barred spiral galaxy located within the constellation Virgo, approximately 68 million light-years away from Earth. It was discovered by Charles Messier on April 15, 1779 and is one of four barred spiral galaxies that appear in Messier's catalogue. M58 is one of the brightest galaxies in the Virgo Cluster. From 1779 it was arguably (though unknown at that time) the farthest known astronomical object until the release of the New General Catalogue in the 1880s and even more so the publishing of redshift values in the 1920s.
Charles Messier discovered Messier 58, along with the elliptical galaxies Messier 59 and Messier 60, on April 15, 1779. M58 was reported on the chart of the Comet of 1779 as it was almost on the same parallel as the star Epsilon Virginis. Messier described M58 as a very faint nebula in Virgo which would disappear in the slightest amount of light he used to illuminate the micrometer wires. This description was later contradicted by John Herschel’s observations in 1833 where he described it as a very bright galaxy, especially towards the middle. Herschel’s observations were also similar to the descriptions of both John
NGC 1156 is a dwarf irregular galaxy in the Aries constellation of the type ibm. It is considered a Magellanic-type irregular. The galaxy has a larger than average core, and contains zones of contra-rotating gas. The counter-rotation is thought to be the result of tidal interactions with another gas rich galaxy some time in the past.
The AGES survey has discovered a candidate dark galaxy close to NGC 1156, one of only a few so far found.
It has a H II nucleus.
NGC 891 (also known as Caldwell 23) is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.
The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures.
In 1999, the Hubble Space Telescope imaged NGC 891 in infrared.
In 2005, due to its attractiveness and scientific interest, NGC 891 was selected to be the first light image of the Large Binocular Telescope. In 2012, it was again used as a first light image of the Discovery Channel Telescope with the Large Monolithic Imager.
Supernova SN 1986J was discovered on August 21, 1986 at apparent magnitude 14.
Although this galaxy looks as we think our own galaxy would look like when viewed edge-on, recent high-resolution images of its dusty disk show unusual filamentary. These patterns are extending into the halo of the galaxy, away from its galactic disk. Scientists presume that supernova explosions caused this interstellar dust to be thrown out of the
The Sculptor Dwarf Irregular Galaxy (SDIG) is an irregular galaxy in the constellation Sculptor. The galaxy was discovered in 1976.
The Sculptor Dwarf Irregular Galaxy and the dwarf galaxy UGCA 442 are both companions of the spiral galaxy NGC 7793. These galaxies all lie within the Sculptor Group, a weakly bound, filament-like group of galaxies located near the Local Group.
The Canis Major Dwarf Galaxy is a hypothetical galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.
The galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all.
The Canis Major Dwarf Galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way, being located about 25,000 light-years away from our Solar System and 42,000 light-years from the Galactic Center. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our location in the Milky Way.
The existence of a strong elliptical-shaped stellar over-density was reported in November 2003 by an international team of French, Italian, British and Australian astronomers, who claimed their study pointed to a newly discovered dwarf galaxy: the Canis Major Dwarf Galaxy. This structure is located closer to the Sun than the center of our Galaxy, at approximately 7 kpc from the Sun.
The team of astronomers that discovered it were collaborating on
ESO 510-G13 is a spiral galaxy approximately 150 million light-years away in the constellation Hydra. The equatorial dust cloud is heavily warped; this may indicate that ESO 510-G13 has interacted with another galaxy. If this is the case, it would provide an excellent illustration of the distortion caused by interacting galaxies, discussed in the article Galaxy formation and evolution under the Spiral galaxy heading.
This galaxy was examined by the Hubble Space Telescope in 2001.
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away in the constellation Ursa Major. Due to its proximity to Earth, large size and active galactic nucleus (which harbors a 70 million M☉ supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also make it a popular target for amateur astronomers.
Messier 81 was first discovered by Johann Elert Bode in 1774. Consequently, the galaxy is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, which was subsequently listed in the Messier Catalogue.
Most of the emission at infrared wavelengths originates from interstellar dust. This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation regions. The general explanation is that the hot, short-lived blue stars that are found within star formation regions are very effective at heating the dust and hence enhancing the infrared dust emission from these regions.
Only one supernova has been detected in Messier 81. The
NGC 1569 is a dwarf irregular galaxy in Camelopardalis. While this faint galaxy is not a popular amateur astronomy target, it is well studied by professional astronomers, who are interested in the history of star formation within the galaxy. The galaxy is relatively nearby. Consequently, the Hubble Space Telescope can easily resolve the stars within the galaxy. The distance to the galaxy was previously believed to be only 2.4 Mpc (7.8 Mly). However, in 2008 scientists studying images from Hubble calculated the galaxy's distance at nearly 11 million light-years away, about 4 million light-years farther than previous thought.
NGC 1569 contains two prominent super star clusters with different histories. Both clusters have experienced episodic star formation. Super star cluster A, located in the northwest of the galaxy, contains young stars (including Wolf-Rayet stars) that formed less than 5 million years ago as well as older red stars. Super star cluster B, located near the center of the galaxy, contains an older stellar population of red giants and red supergiants. Both of these star clusters are thought to have masses equivalent to the masses of the globular clusters in the Milky
NGC 4696 is an elliptical galaxy. It lies around 150 million light years away in the constellation Centaurus. It is the brightest galaxy in the Centaurus Cluster, a large, rich cluster of galaxies in the constellation of the same name. The galaxy is surrounded by many dwarf elliptical galaxies also located within the cluster.
am 0644-741 is an unbarred lenticular galaxy, and a ring galaxy, which is 300 million light-years away in the direction of the southern constellation Volans. The yellowish nucleus was once the center of a normal spiral galaxy, and the ring which currently surrounds the center is 150,000 light-year diameter. The ring is theorized to have formed by a collision with another galaxy, which triggered a gravitational disruption that caused dust in the galaxy to condense and form stars, which forced it to then expand away from the galaxy and create a ring. The ring is a region of rampant star formation dominated by young, massive, hot blue stars. The pink regions along the ring are rarefied clouds of glowing hydrogen gas that is fluorescing as it is bombarded with strong ultraviolet light from the blue stars. Galactic simulation models suggest that the ring of AM 0644-741 will continue to expand for about another 300 million years, after which it will begin to disintegrate.
NGC 2536 is a barred spiral galaxy in the constellation Cancer that is interacting with NGC 2536. The two galaxies are listed together in the Atlas of Peculiar Galaxies as an example of a spiral galaxy with a high surface brightness companion.
NGC 4625 is a distorted dwarf galaxy in the constellation Canes Venatici. The galaxy is formally classified as a Sm galaxy, which means that its structure vaguely resembles the structure of spiral galaxies. The galaxy is sometimes referred to as a Magellanic spiral because of its resemblance to the Magellanic clouds.
Unlike most spiral galaxies, NGC 4625 has a single spiral arm, which gives the galaxy an asymmetric appearance. It has been hypothesized that this galaxy's asymmetric structure may be the result of a gravitational interaction with NGC 4618. Such asymmetric structure is commonly seen among many interacting galaxies. However, observations of neutral hydrogen gas in NGC 4618 and NGC 4625 show that NGC 4625 does not appear to have been affected by the gravitational interaction. This indicates that the single-arm structure seen in NGC 4625 may be created through intrinsic processes.
As mentioned above, NGC 4625 is interacting with NGC 4618.
Messier 59 (also known as M59 or NGC 4621) is an elliptical galaxy in the constellation Virgo.
Messier 59 and the nearby elliptical galaxy Messier 60 were both discovered by Johann Gottfried Koehler in April 1779 during observations of a comet in the same part of the sky. Charles Messier listed both in the Messier Catalogue about three days after Koehler's discovery.
M59 is a member of the Virgo Cluster.
Messier 88 (also known as M88 or NGC 4501) is a spiral galaxy about 47 million light-years away in the constellation Coma Berenices. It was discovered by Charles Messier in 1781.
This galaxy is one of the fifteen Messier objects that belong the nearby Virgo Cluster of galaxies. It is galaxy number 1401 in the Virgo Cluster Catalogue (VCC) of 2096 galaxies that are candidate members of the cluster. This galaxy may be on a highly elliptical orbit that is carrying it toward the cluster center, which is occupied by the giant elliptical galaxy M87. NGC 4501 is currently 0.3–0.48 million parsecs from the center and will come closest to the core in about 200–300 million years. The motion of this galaxy through the intergalactic medium of the Virgo cluster is creating a ram pressure that is stripping away the outer region of neutral hydrogen. This stripping has already been detected along the western, leading edge of the galaxy.
This galaxy is inclined to the line of sight by 64°. It is classified as an Sbc spiral, which lies between the Sb and Sc categories of medium-wound and loosely-wound spiral arms, respectively. The arm structure of the spirals is very regular and can be followed
NGC 55 (also known as Caldwell 72) is a barred irregular galaxy located about 7 million light-years away in the constellation Sculptor. Along with its neighbor NGC 300, it is one the closest galaxies to the Local Group, probably lying between us and the Sculptor Group.
NGC 55 and the spiral galaxy NGC 300 have traditionally been identified as members of the Sculptor Group, a nearby group of galaxies in the constellation of the same name. However, recent distance measurements indicate that the two galaxies actually lie in the foreground.
It is likely that NGC 55 and NGC 300 form a gravitationally bound pair.
The Webb Society Deep-Sky Observer's Handbook, writes the following about NGC 55: "Nearly edge-on and appears asymmetrical with some signs of dust near the bulge, which is diffuse, broad and somewhat elongated with the south edge sharp; southeast of the bulge it is strongly curved and lined with 4 or 5 faint knots; north edge of the curve is sharp." Burnham calls it "one of the outstanding galaxies of the southern heavens", somewhat resembling a smaller version of the Large Magellenic Cloud.
The Small Magellanic Cloud (SMC) is a dwarf galaxy. It has a diameter of about 7,000 light-years and contains several hundred million stars. It has a total mass of approximately 7 billion times the mass of our Sun.
Some speculate that the SMC was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. It contains a central bar structure.
At a distance of about 200,000 light-years, it is one of the Milky Way's nearest neighbors. It is also one of the most distant objects that can be seen with the naked eye.
With a mean declination of approximately -73 degrees, it can only be viewed from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere. It is located in the constellation of Tucana and appears as a hazy, light patch in the night sky about 3 degrees across. It looks like a detached piece of the Milky Way. Since it has a very low surface brightness, it is best viewed from a dark site away from city lights.
It forms a pair with the Large Magellanic Cloud (LMC), which lies a further 20 degrees to the east. The Small Magellanic Cloud is a member of the Local Group.
In the southern hemisphere, the Magellanic clouds have long
RXJ1242-11 is an elliptical galaxy located approximately 200 megaparsecs (about 650 million light-years) from Earth. According to current interpretations of X-ray observations made by the Chandra X-ray Observatory and XMM-Newton, the centre of this galaxy is a 100 million solar mass supermassive black hole which was observed to have tidally disrupted a star. The discovery is widely considered to be the first strong evidence of a supermassive black hole ripping apart a star and consuming a portion of it .
NGC 4603 is a spiral galaxy located in the constellation Centaurus. It has been found to contain over 36 Cepheid variable stars, being the most distant galaxy the Hubble Space Telescope has found to contain Cepheid variable stars.
Cetus Dwarf is a dwarf spheroidal galaxy. It lies approximately 2.46 Million light-years from Earth. It is an isolated galaxy of the Local Group, which also contains the Milky Way. All of the most readily observable stars in the galaxy are red giants.
The Cetus Dwarf was discovered in 1999 by Alan Whiting, George Hau and Mike Irwin and was found to be a member of the Local Group.
As of 2000, no known neutral hydrogen gas has been found that is related to the Cetus dwarf galaxy.
The Comet Galaxy is a spiral galaxy located 3.2 billion light-years from Earth, in the galaxy cluster Abell 2667, was found with the Hubble Space Telescope. This galaxy has a little more mass than our Milky Way. It was detected on 2 March 2007.
The unique galaxy, which is situated 3.2 billion light-years from the Earth, has an extended stream of bright blue knots and diffuse wisps of young stars. This spiral galaxy rushes with 3.5 million km/h through the cluster Abell 2667 and thereby like a comet shows a tail with a length of 600,000 light years.
The comet galaxy is currently being ripped to pieces. Moving through a cluster at speeds of greater than 2 million mph, is one of the main reasons the gas and stars of the galaxy are being stripped away by the tidal forces of the cluster. Other factors adding to the damage of the galaxy are the cluster's scorching gas plasma. As the galaxy speeds through, its gas and stars are still being stripped away by the tidal forces exerted by the cluster - just as the tidal forces exerted by the moon and Sun push and pull the Earth's oceans. Also contributing to this destructive process is the pressure of the cluster's hot gas plasma reaching
IC 1613 (also known as Caldwell 51) is an irregular dwarf galaxy in the constellation Cetus near the star 26 Ceti. It was discovered in 1906 by Max Wolf, and is approaching Earth at 234 km/s.
IC 1613 is a member of our Local Group. It has played an important role in the calibration of the Cepheid variable period luminosity relation for estimating distances. Other than the Magellanic Clouds, it is the only Local Group dwarf irregular galaxy where RR Lyrae-type variables have been observed.
In 1999, Cole et al. used the Hubble Space Telescope to find that the dominant population of this galaxy has an age of ~7 Gyr. Using its Hess diagram, they found that its evolutionary history may be similar to that of the Pegasus Dwarf Irregular Galaxy. Both galaxies are classified as Ir V in the DDO system. Also in 1999, Antonello et al. found five cepheids of Population II in IC 1613, giving self-evident support for the existence of a very old stellar population component of IC 1613. In 1999, King, Modjaz, & Li discovered the first nova ever detected in IC 1613.
Messier 61 (also known as M61 or NGC 4303) is a spiral galaxy in the Virgo Cluster. It was discovered by Barnabus Oriani on May 5, 1779.
M61 is one of the larger members of the Virgo Cluster.
Six supernovae have been observed in this galaxy:
NGC 4725 is an intermediate barred spiral galaxy about 40 million light-years away in the constellation Coma Berenices. NGC 4725 is a Seyfert Galaxy, suggesting an active galactic nucleus containing a supermassive black hole.
The Aquarius Dwarf galaxy is a dwarf galaxy and an irregular galaxy, that was first catalogued in 1959 by the DDO survey. Its most distinctive characteristic is that it is one of the few galaxies known to display a blueshift, as it is traveling towards the Milky Way at 137 km/s. Aquarius dwarf is also part of the Aquarius constellation.
Lee et al. 1999 firmly established AqrDIG as a member of the Local Group and derived a distance, using the tip of the red giant branch, of 950 ± 50 kpc. Its distance from the group's barycenter is also calculated to be 950 kpc, which means that AqrDIG is rather isolated in space. Compared to the even further away SagDIG, it is much less luminous.
IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by Lewis Swift in 1887. Nicholas U. Mayall was the first to suggest that the object is extragalactic in 1935. Edwin Hubble suspected it might belong to the Local Group of galaxies, but its status remained uncertain for decades. The radial velocity of IC 10 was measured in 1962, and it was found to be approaching the Milky Way at approximately 350 km/s, strengthening the evidence for its membership in the Local Group. Its membership in the group was finally confirmed in 1996 by direct measurements of its distance based on observations of Cepheids. Despite its closeness, the galaxy is rather difficult to study because it lies near the plane of the Milky Way and is therefore heavily obscured by interstellar matter.
The apparent distance between IC 10 and the Andromeda Galaxy is about the same as the apparent distance between the Andromeda Galaxy and the Triangulum Galaxy, which suggests that IC 10 may belong to the M31 subgroup.
IC 10 is the only known starburst galaxy in the Local Group of galaxies. It has many more Wolf-Rayet stars per square kiloparsec (5.1 stars/kpc²) than the Large Magellanic Cloud
Messier 105 (also known as M105 and NGC 3379) is an elliptical galaxy in the constellation Leo. Messier 105 is known to have a supermassive black hole.
Messier 105 was discovered by Pierre Méchain on 24 March 1781, just a few days after he discovered the nearby galaxies Messier 95 and Messier 96. This galaxy is one of several that were not originally included in the original Messier Catalogue compiled by Charles Messier. Messier 105 was included in the catalog only when Helen S. Hogg found a letter by Méchain describing Messier 105 and when the object described by Méchain was identified as a galaxy previously named NGC 3379.
Messier 105 is one of several galaxies within the M96 Group, a group of galaxies in the constellation Leo. The group also includes the Messier objects M95 and M96.
Messier 86 (also known as M86 or NGC 4406) is a lenticular galaxy in the constellation Virgo. It was discovered by Charles Messier in 1781. M86 lies in the heart of the Virgo Cluster of galaxies and forms a most conspicuous group with another giant, Lenticular Galaxy M84. It displays the highest blue shift of all Messier objects, as it is approaching the Milky Way at 244 km/s. This is due to its falling towards the center of the Virgo cluster from the opposite side, which causes it to move in the direction of the Milky Way.
In popular culture - In the TV show Andromeda, M86 is cited as being the origin of the Magog invasion of the three galaxies in the season 2 opener "The Widening Gyre"
Messier 87 (also known as M87, Virgo A or NGC 4486) is a supergiant elliptical galaxy. It was discovered in 1781 by the French astronomer Charles Messier, who cataloged it as a nebulous feature. The second brightest galaxy within the northern Virgo Cluster, it is located about 16.4 million parsecs (53.5 million light-years) from Earth. Unlike a disk-shaped spiral galaxy, Messier 87 has no distinctive dust lanes and it has an almost featureless, ellipsoidal shape that diminishes in luminosity with distance from the center. At the core is a supermassive black hole, which forms the primary component of an active galactic nucleus. This object is a strong source of multiwavelength radiation, particularly radio waves. A jet of energetic plasma originates at the core and extends outward at least 1,500 parsecs (5,000 light-years).
The stars in this galaxy form about one sixth of Messier 87's mass. They have a nearly spherically symmetric distribution, while the density of stars decreases with increasing distance from the core. The galactic envelope extends out to a radius of about 150 kpc (490 kly), where it has been truncated—possibly by an encounter with another galaxy. Between the stars
NGC 2787 is a barred lenticular galaxy approximately 24 million light-years away in the constellation Ursa Major. In 1999, the Hubble Space Telescope took a look at NGC 2787.
NGC 2787 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms. LINERs are very common within lenticular galaxies, approximately one-fifth of nearby lenticular galaxies contain LINERs.
NGC 2915 is a blue dwarf galaxy located 12 million light-years away, right on the edge of the Local Group. The optical galaxy corresponds to the core of a much larger spiral galaxy traced by radio observation of neutral hydrogen.
The galaxy has a short central bar, much like the Milky Way and very extended spiral arms.
The reason for the spiral arms and majority of the galaxy's disk to be still neutral hydrogen (as opposed to have formed stars) is not well-understood but is thought to be related to the galaxy's isolation, in that it has no nearby satellite galaxies and no nearby major galaxies to force star formation.
NGC 4027 (also known as Arp 22) is a barred spiral galaxy approximately 83 million light-years away in the constellation Corvus. It is also a peculiar galaxy because one of its spiral arms goes out more than the other. This is probably due to a galactic collision in NGC 4027's past.
NGC 4027 is part of the NGC 4038 Group, a group of galaxies that also contains the Antennae Galaxies (NGC 4038/NGC 4039).
NGC 4622 is a face-on spiral galaxy located in the constellation Centaurus.
The spiral galaxy, NGC4622 (also called backward galaxy), lies 111 million light years away in the constellation Centaurus. NGC 4622 is an example of a galaxy with leading spiral arms. In spiral galaxies, spiral arms were thought to trail; the tips of the spiral arms winding away from the center of the galaxy in the direction of the disks orbital rotation. In NGC4622, however, the outer arms are leading spiral arms; the tips of the spiral arms point towards the direction of disk rotation. This may be the result of a gravitational interaction between NGC 4622 and another galaxy or the result of a merger between NGC 4622 and a smaller object.
NGC 4622 also has a single inner trailing spiral arm. Although it was originally suspected that the inner spiral arm was a leading arm, the observations that established that the outer arms were leading also established that the inner arm was trailing.
These results were met with skepticism in part because they contradicted conventional wisdom with one quote being “so you’re the backward astronomers who found the backward galaxy.” The fact that a pair of arms could lead
The Sculptor Galaxy (also known as the Silver Coin or Silver Dollar Galaxy, NGC 253, or Caldwell 65) is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.
The galaxy was discovered by Caroline Herschel in 1783 during one of her systematic comet searches. About half a century later, John Herschel observed it using his 18 inch metallic mirror reflector at the Cape of Good Hope. He wrote, "very bright and large (24′ in length); a superb object.... Its light is somewhat streaky, but I see no stars in it except 4 large and one very small one, and these seem not to belong to it, there being many near..."
In 1961 Allan Sandage wrote in the Hubble Atlas of Galaxies that the Sculptor Galaxy is "the prototype example of a special subgroup of Sc systems....photographic images of galaxies of the group are dominated by the dust pattern. Dust lanes and patches of great complexity are scattered throughout the surface. Spiral arms are often difficult to trace.... The arms are defined as much by the dust as by the spiral pattern." Bernard Y. Mills, working out of
The Sextans Dwarf Spheroidal is a dwarf spheroidal galaxy that was discovered in 1990 by Mike Irwin, M.T. Bridgeland, P.S. Bunclark and R.G. McMahon as the 8th satellite of the Milky Way, and is named fittingly, as it is located in the constellation of Sextans. It is also an elliptical galaxy, and displays a redshift because it is receding from the Milky Way at 224 km/s.
The Andromeda Galaxy (/ænˈdrɒmɨdə/) is a spiral galaxy approximately 2.5 million light-years (2.4×10 km) from Earth in the Andromeda constellation. Also known as Messier 31, M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our Milky Way galaxy, but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, the Andromeda Galaxy may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and could be the most massive in the grouping. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (10) stars: at least twice the number of stars in the Milky Way galaxy, which is estimated to be 200–400 billion.
The Andromeda Galaxy is estimated to be 7.1×10 solar masses. In comparison a 2009 study estimated that the Milky Way
The Black Eye Galaxy (also called Sleeping Beauty Galaxy; designated Messier 64, M64, or NGC 4826) was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier in 1780. It has a spectacular dark band of absorbing dust in front of the galaxy's bright nucleus, giving rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy. M64 is well known among amateur astronomers because of its appearance in small telescopes. It is a spiral galaxy in the Coma Berenices constellation.
At first glance, M64 seems to be a fairly normal spiral galaxy. As in the majority of galaxies, all of the stars in M64 are orbiting in the same direction, clockwise as seen in the Hubble image.
However, recent detailed studies have led to the remarkable discovery that the interstellar gas in the outer regions of M64 rotates in the opposite direction from the gas and stars in the inner regions. The inner region has a radius of only approximately 3,000 light-years, while the outer section extends another 40,000 light-years. This pattern is believed to trigger the creation of many new stars around the boundary separating the two
Centaurus A (also known as NGC 5128) is a prominent galaxy in the constellation of Centaurus. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type (lenticular galaxy or a giant elliptical galaxy) and distance (10-16 million light-years). NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth brightest in the sky, making it an ideal amateur astronomy target, although the galaxy is only visible from low northern latitudes and the southern hemisphere.
The center of the galaxy contains a supermassive black hole weighing in at 55 million solar masses, which ejects a relativistic jet that is responsible for emissions in the X-ray and radio wavelengths. By taking radio observations of the jet separated by a decade, astronomers have determined that the inner parts of the jet are moving at about one half of the speed of light. X-rays are produced farther out as the jet collides with surrounding gases resulting in the creation of highly energetic particles. The radio jets of Centaurus A are over a million light
Messier 94 (also known as NGC 4736) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped. The galaxy is also notable in that it has two ring structures.
M94 is classified as having a low ionization nuclear emission region (LINER) nucleus. LINERs in general are characterized by optical spectra that reveal that ionized gas is present but the gas is only weakly ionized (i.e. the atoms are missing relatively few electrons).
M94 contains both an inner ring with a diameter of 70" and an outer ring with a diameter of 600". These rings appear to form at resonance locations within the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star formation is fueled by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure.
A 2009 study conducted by an international team of astrophysicists revealed that the outer ring of M94 is not a closed stellar ring, as historically
NGC 247 (also known as Caldwell 62) is an Intermediate spiral galaxy about 11.1 Mly away in the constellation Cetus. This distance was confirmed in late February 2011. Previous measurements showed that the galaxy was about 12.2 Mly away, but was proved to be wrong. NGC 247 is a member of the Sculptor Group.
NGC 247 is one of several galaxies that is gravitationally bound to the Sculptor Galaxy (NGC 253). These galaxies form a small core in the center of the Sculptor Group, which is one of the nearest groups of galaxies to the Milky Way. Most other galaxies associated with the Sculptor Group are only weakly gravitationally bound to this core.
The news regarding the distance error:
NGC 2841 is an inclined unbarred spiral galaxy in the constellation Ursa Major. Initially thought to be about 30 million light years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined that it was approximately 14.1 megaparsecs or 46 million light years distant. Structurally, NGC 2841 is noted for its large population of young blue stars, and few H II regions.
NGC 2841 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms.
NGC 3227 is a spiral galaxy that is interacting with the dwarf elliptical galaxy NGC 3226. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo.
Sir William Herschel already recognised them as a 'double nebula' and they were jointly listed as Holm 187 in the Catalogue of Double and Multiple Galaxies and as Arp 94 in the Atlas of Peculiar Galaxies. Amateur telescopes can discern them but require magnification of about 100 times. They are situated 50′ east of the well-known double star system Gamma Leonis (i.e. Algieba).
NGC 3227 contains a Seyfert nucleus, a type of active galactic nucleus (AGN). Such Seyfert nuclei typically contain supermassive black holes.
As is typical of many AGN, the nucleus of NGC 3227 has been identified as a source of variable X-ray emission. This variability occurs on time scales ranging from a few hours to a few months. The variability may be caused by variations in the density or ionization of gas and dust near the AGN that absorb the X-ray emission. A substantial amount of the X-ray-absorbing gas may lie within 0.4
NGC 6822 (also known as Barnard's Galaxy, IC 4895, or Caldwell 57) is a barred irregular galaxy approximately 1.6 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1881 (hence its name), with a six-inch refractor telescope. It is one of the closer galaxies to the Milky Way. It is similar in structure and composition to the Small Magellanic Cloud.
Edwin Hubble wrote the seminal paper N.G.C. 6822, A Remote Stellar System (Hubble 1925) wherein he identified 15 variable stars (11 of which were Cepheids). He also surveyed the galaxy's stars distribution down to magnitude 19.4. He provided spectral characteristics, luminosities and dimensions for the five brightest "diffuse nebula" (giant H II regions) that included the Bubble Nebula and the Ring Nebula. He also computed the absolute magnitude of the entire galaxy.
Hubble's detection of eleven Cepheid variable stars was a milestone in astronomy. Utilizing the Cepheid Period-Luminosity relationship, Hubble determined a distance of more than 700,000 light-years. This was the first system beyond the Magellanic Clouds to have its distance accurately
Pisces Dwarf is an irregular dwarf galaxy that is part of the Local Group. The galaxy is also suspected of being a satellite galaxy of the Triangulum Galaxy (M33). Because it is in the constellation Pisces, the galaxy is called the Pisces Dwarf. It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.
It was discovered by Karachentseva in 1976.
A study of the star formation history conducted by Miller et al. 2001 provide much information on how this galaxy developed. Apparently, the star formation rate in the Pisces Dwarf has been declining for the past 10 billion years. Most of the galaxy's stars were formed in its early years, about 8 billion years ago. The Miller study has also shown that there has been no significant star formation for the past 100 million years. Hence, most of the stars that populate this galaxy are old, metal-rich stars aged about 2.5 billion years. But there are small clusters of young, hot, blue stars on the outer areas of the galaxy.
NGC 6872 and IC 4970 are a set of interacting galaxies over 200 million light-years away in the constellation Pavo.
On March 29, 1999, the European Southern Observatory (ESO) took a look at these galaxies. It shows the spectacular barred spiral galaxy NGC 6872 that is shaped like an "integral sign". It is of type SB(s)b pec and is accompanied by a smaller, interacting galaxy, IC 4970 of type E7-S0 One of NGC 6872 spiral arms is significantly disturbed and is populated by a plethora of bluish objects, many of which are star-forming regions. This may have been be caused by a recent passage of IC 4970 through it. The whole of NGC 6872 extends over more than 6 arcmin in the sky and its real size from tip to tip is thus nearly 380,000 light years. It is in fact one of the largest known barred spiral galaxies.
Messier 60 (also known as NGC 4649) is an elliptical galaxy approximately 55 million light-years away in the constellation Virgo.
Messier 60 and the nearby galaxy Messier 59 were both discovered by Johann Gottfried Koehler in April 1779 during observations of a comet in the same part of the sky. Charles Messier listed both in the Messier Catalogue about three days after Koehler's discovery.
NGC 4647 appears approximately 2′.5 away from Messier 60; the optical disks of the two galaxies overlap. Although this overlap suggests that the galaxies are interacting, photographic images of the two galaxies do not reveal any evidence for gravitational interactions between the two galaxies as would be suggested if the two galaxies were physically close to each other. This suggests that the galaxies are at different distances and are only weakly interacting if at all.
M60 is the third-brightest giant elliptical galaxy of the Virgo cluster of galaxies, and is the dominant member of a subcluster of four galaxies, which is the closest-known isolated compact group of galaxies.
A supernova (SN 2004W) was observed in Messier 60.
At the center of M60 is a black hole of 4.5 billion solar masses, one
Part of the M81 group, NGC 2976, located 1° 20′ southwest of M81, is an unbarred spiral galaxy. The inner structure contains many dark lanes and stellar condensations in its disk. The galaxy is sometimes classified as Sdp because its spiral arms are difficult to be traced. The bright inner part of this disk appears to have a defined edge. These distortions are results from the gravitational interactions with its neighbors.
NGC 2976 was discovered by William Herschel on November 8, 1801, and cataloged as H I.285.
NGC 4216 is a metal-rich intermediate spiral galaxy located not far from the center of the Virgo Cluster of galaxies, roughly 40 million light-years away. It's seen nearly edge-on.
It's one of the largest and brightest spiral galaxies of the Virgo Cluster, with an absolute magnitude that has been estimated to be -22 (ie: brighter than the Andromeda Galaxy), and like most spiral galaxies of this cluster shows a deficiency of neutral hydrogen that's concentrated within the galaxy's optical disk and has a low surface density for a galaxy of its type. If fact, its disk shows pillar-like structures that may have been caused by interactions with the intracluster medium of Virgo and/or with nearby galaxies
In NGC 4216's halo, besides a rich system of globular clusters that may be up to five times more populous than that of our galaxy, are present two stellar streams that are interpreted as two satellite galaxies being disrupted and absorbed by this galaxy.
The Sunflower Galaxy (also known as Messier 63, M63, or NGC 5055) is a spiral galaxy in the constellation Canes Venatici consisting of a central disc surrounded by many short spiral arm segments. The Sunflower Galaxy is part of the M51 Group, a group of galaxies that also includes the Whirlpool Galaxy (M51).
The Sunflower Galaxy was discovered by Pierre Méchain on June 14, 1779. The galaxy was then listed by Charles Messier as object 63 in the Messier Catalogue.
In the mid-19th century, Lord Rosse identified spiral structures within the galaxy, making this one of the first galaxies in which such structure was identified.
In 1971, a supernova with a magnitude of 11.8 appeared in one of the arms of M63.
The Cartwheel Galaxy (also known as ESO 350-40) is a lenticular galaxy about 500 million light-years away in the constellation Sculptor. It is an estimated 150,000 light-years across, has a mass of about 2.9–4.8 × 10 solar masses, and rotates at 217 km/s.
It was discovered by Fritz Zwicky in 1941. Zwicky considered his discovery to be "one of the most complicated structures awaiting its explanation on the basis of stellar dynamics."
An estimation of the galaxy's span resulted in a conclusion of 150,000 light years, which is slightly larger than the Milky Way.
The Cartwheel galaxy shows non-thermal radio and optical spokes, but they are not the same spokes.
The galaxy was once a normal spiral galaxy before it apparently underwent a head-on collision with a smaller companion approximately 200 million years ago (i.e., 200 million years prior to the image). When the nearby galaxy passed through the Cartwheel Galaxy, the force of the collision caused a powerful shock wave through the galaxy, like a rock being tossed into a sandbed. Moving at high speed, the shock wave swept up gas and dust, creating a starburst around the galaxy's center portion that were unscathed. This explains the
IC 1296 is a barred spiral galaxy in the constellation Lyra. It is a low surface brightness galaxy that lies in line of sight 4' to the northwest of the more famous planetary nebula M57 Ring Nebula. IC 1296 is much farther away - an estimated distance of ~221-million lightyears (NED data) as compared to M57's mere 2300LY.
NGC 1232 is an intermediate spiral galaxy about 60 million light-years away in the constellation Eridanus.
It is dominated by millions of bright stars and dark dust, in spiral arms rotating about the center. Open clusters containing bright blue stars are sprinkled along these spiral arms, with dark lanes of dense interstellar dust between. Less visible are dim normal stars and interstellar gas, producing such high mass that they dominate the dynamics of the inner galaxy. Not visible is matter of unknown form called dark matter, needed to explain the motions of the visible material in the outer galaxy.
NGC 1232 and its satellite are part of the Eridanus cluster of galaxies, along with NGC 1300.
NGC 1232A is a satellite galaxy of NGC 1232. It is thought to be the cause of unusual bending in the spiral arms. In 1988, NGC 1232A was estimated to be 68 million light-years away while NGC 1232 was estimated to be 65 million light-years away.
NGC 4395 is a low surface brightness spiral galaxy with a halo that is about 8′ in diameter. It has several wide areas of greater brightness running northwest to southeast. The one furthest southeast is the brightest. Three of the patches have their own NGC numbers: 4401, 4400, and 4399 running east to west.
NGC 4395 is notable in that it contains one of the smallest supermassive black hole ever discovered. The central black hole has a mass of "only" 300,000 sun masses. The black hole was discovered in 1989, and had been judged to be between 55,000 and 65,000 sun masses. Recent estimates have thus quintupled the estimated size, but it is still far smaller than other black holes in its class. It is likely that is it so small because it has little material around it to add to its bulk. Indeed, stars are conspicuously absent in its immediate vicinity, and so it was "starved" down to that size or has never been able to fully grow, unlike most similar black holes.
NGC 4414 is an unbarred spiral galaxy about 62 million light-years away in the constellation Coma Berenices. It is a flocculent galaxy, with short segments of spiral structure but without the dramatic well-defined spiral arms of a grand design spiral. In 1974 a supernova, SN 1974G, was observed and is the only supernova in this galaxy to be recorded so far.
It was imaged by the Hubble Space Telescope in 1995, as part of the HST's main mission to determine the distance to galaxies, and again in 1999 as part of the Hubble Heritage project. It has been part of an ongoing effort to study its Cepheid variable stars. The outer arms appear blue due to the continuing formation of young stars and include a possible Luminous Blue Variable with an absolute magnitude of -10
NGC 4414 is also a very isolated galaxy without signs of past interactions with other galaxies and despite not being a starburst galaxy shows a high density and richness of gas -both atomic and molecular, with the former extending far beyond its optical disk-
NGC 6240 is a well-studied nearby ultraluminous infrared galaxy (ULIRG) in the constellation Ophiuchus. The galaxy is the remnant of a merger between two smaller galaxies. The collision between the two progenitor galaxies has resulted in a single larger galaxy with two distinct nuclei and a highly disturbed structure, including faint extensions and loops.
The power sources of ULIRGs in general has been greatly debated. Infrared light from galaxies generally originates from dust in the interstellar medium. ULIRGs are notable in that they are abnormally bright in the infrared. The infrared dust emission in ULIRGs is over one trillion times more luminous than the Sun (i.e. it has an infrared luminosity of 10 L☉). Astronomers have speculated that either intense star formation regions or active galactic nuclei (which contain supermassive black holes) may be responsible for the intense dust heating that produces this emission, although the general consensus is that both may be present in most ULIRGs. Studying the exact nature of ULIRGs has been difficult, however, because the dust in the centers of these galaxies obscures both visible and near-infrared starlight and because theoretical
NGC 7793 is a spiral galaxy about 12.7 million light-years away in the constellation Sculptor. It was discovered in 1826 by James Dunlop.
NGC 7793 is one of the brightest galaxies within the Sculptor Group, a group of galaxies in the constellation of the same name. The group itself is an elongated, loosely bound group of galaxies with the Sculptor Galaxy (NGC 253) and its companion galaxies forming a tightly-bound core of galaxies near the center.
On March 25, 2008, SN 2008bk was discovered in NGC 7793. At apparent magnitude 12.5, it became the 2nd brightest supernova of 2008.
A black hole about the size of our sun in the outer spiral of this galaxy has some spectacular jets.
NGC 147 (also known as DDO3 or Caldwell 17) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a physical pair with the nearby galaxy NGC 185, another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185 (and therefore has a considerably lower surface brightness). This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook, the visual appearance of NGC 147 is described as follows:
Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.
The membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch (2.5 m) telescope at Mount Wilson near Los Angeles.
A survey of the brightest asymptotic giant branch (AGB) stars in the area of radius 2′ from the center of NGC 147 shows that the last significant star-forming activity in NGC 147 occurred
NGC 4945 is a spiral galaxy in the constellation Centaurus. It is thought to be quite similar to the Milky Way Galaxy, but X-ray observations show that NGC 4945 has an unusual, energetic, Seyfert 2 nucleus that might house a large black hole. It was discovered by James Dunlop in 1826.
NGC 4945 one of the brightest galaxies within the Centaurus A/M83 Group, a large, nearby group of galaxies. The galaxy is the second brightest galaxy within the subgroup centered on Centaurus A.
A starburst galaxy is a galaxy in the process of an exceptionally high rate of star formation, compared to the usual star formation rate seen in most galaxies. Galaxies are often observed to have a burst of star formation after a collision or close encounter between two galaxies. The rate of star formation is so great for a galaxy undergoing a starburst that, if the rate was sustained, the gas reservoirs from which stars are formed would be used up on timescales much shorter than the age of the galaxy. For this reason, it is presumed that starbursts are temporary. Well-known starburst galaxies include M82, NGC 4038/NGC 4039 (the Antennae Galaxies), and IC 10.
Several definitions of the term starburst galaxy exist and there is no strict definition on which all astronomers agree. However, many generally agree that the definition must in some way be related to these three factors:
Commonly used definitions include:
Essentially to ignite a starburst, it is necessary to concentrate a large amount of cool molecular gas in a small volume. Such concentrations and perturbations are strongly suspected to cause global starburst phenomena in major galaxy mergers, although the exact mechanisms
Andromeda IV (And IV) might be an irregular satellite of the Andromeda Galaxy; however it is more probably not a galaxy at all, but a loosely bound star cluster or some other background feature.
It was discovered by Sidney van den Bergh.
Messier 96 (also known as NGC 3368) is an intermediate spiral galaxy about 31 million light-years away in the constellation Leo. It was discovered by French astronomer Pierre Méchain on March 20, 1781. After communicating his finding, French astronomer Charles Messier confirmed the finding four days later and added it to his catalogue of nebulous objects. Finding this object is extremely difficult with binoculars. With a telescope of 25.4 cm (10.0 in) aperture, the galaxy is visible as a 3 × 5 arcminute halo with a brighter core region.
This complex galaxy is inclined by an angle of about 53° to the line of sight from the Earth, which is oriented at a position angle of 172°. It is categorized as a double-barred spiral galaxy with a small inner bulge through the core along with an outer bulge. The nucleus displays a weak level of activity of the LINER2 type. Variations in ultraviolet emission from the core suggest the presence of a supermassive black hole. Estimates for the mass of this object range from 1.5×10 to 4.8×10 times the mass of the Sun.
On May 9, 1998 a supernova event was observed in this galaxy. Designated SN 1998bu, this was a Type Ia supernova explosion. It reached
NGC 1850 is an open cluster in the Dorado constellation. It was discovered by James Dunlop in 1826. It is an unusual cluster of stars because the distribution of its stars is like a globular cluster, but unlike the globular clusters of the Milky Way it is composed of young stars. Thus, it is a cluster of stars like no known cluster of stars in our galaxy.
NGC 2207 and IC 2163 are a pair of colliding spiral galaxies about 80 million light-years away in the constellation Canis Major. Both galaxies were discovered by John Herschel in 1835. So far three supernovae have been observed in NGC 2207 (SN 1975A, SN 1999ec and SN 2003H). NGC 2207 is in the process of tidal stripping IC 2163.
In November 1999, the Hubble Space Telescope took a look at these galaxies.
In April 2006, the Spitzer Space Telescope also took a look at these galaxies (Picture seen below).
NGC 2207 is in the process of colliding and merging with IC 2163. But unlike the Antennae or the Mice Galaxies, they are still two separate spiral galaxies. They are only in the first step of colliding and merging. Soon they will collide, probably looking a bit more like the Mice Galaxies. In about a billion years time they are expected to merge and become an elliptical galaxy.
NGC 4151 is an intermediate spiral Seyfert galaxy located 43 million light years from Earth in the constellation Canes Venatici. The galaxy was first mentioned by William Herschel on March 17, 1787; it was one of the two Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively-growing supermassive black hole; it was determined in 2012 that there are two black holes, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period.
X-ray emission from NGC 4151 was apparently first detected on December 24, 1970, with the X-ray observatory satellite Uhuru, although the observation spanned an error-box of 0.56 square degrees and there is some controversy as to whether UHURU might not have detected the BL Lac object 1E 1207.9 +3945, which is inside their error box - the later HEAO 1 detected an X-ray source of NGC 4151 at 1H 1210+393, coincident with the optical position of the nucleus and outside the error box of.
To explain the X-ray emission two different possibilities have been proposed:
NGC 4565 (also known as the Needle Galaxy or Caldwell 38) is an edge-on spiral galaxy about 30 to 50 million light-years away in the constellation Coma Berenices.
The 10th magnitude galaxy sits perpendicular to our own Milky Way galaxy and is almost directly above the North Galactic Pole (in the same way Polaris is located above the Earth's North Pole).
It is known as the Needle Galaxy for its narrow profile. First spotted in 1785 by Sir William Herschel (1738–1822), this is one of the most famous examples of an edge-on spiral galaxy. "Visible through a small telescope, some sky enthusiasts consider NGC 4565 to be a prominent celestial masterpiece Messier missed."
Much speculation exists in the literature as to the nature of the central bulge. In the absence of clear-cut dynamical data on the motions of stars in the bulge, the photometric data alone cannot adjudge among various options put forth. However, its exponential shape suggests that it is a barred spiral galaxy.
NGC 5474 is a peculiar dwarf galaxy in the constellation Ursa Major. It is one of several companion galaxies of the Pinwheel Galaxy (M101), a grand-design spiral galaxy. Among the Pinwheel Galaxy's companions, this galaxy is the closest to the Pinwheel Galaxy itself. The gravitational interaction between NGC 5474 and the Pinwheel Galaxy have strongly distorted the galaxy. As a result, the disk is offset relative to the nucleus. The star formation in this galaxy (as traced by hydrogen spectral line emission) is also offset from the nucleus. NGC 5474 shows some signs of a spiral structure. As a result, this galaxy is often classified as a dwarf spiral galaxy, a relative rare group of dwarf galaxies.
The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group galaxies makes it an important object for study.
The Tucana Dwarf is a dwarf spheroidal galaxy of type dE5. It contains only old stars, formed in a single star formation era around the time the Milky Way's globular clusters formed. It is not experiencing any current star formation, unlike other isolated dwarf galaxies.
The Tucana Dwarf does not contain very much neutral hydrogen gas. It has a metallicity of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy. There does not seem to be any substructure to the stellar distribution in the galaxy.
The Tucana Dwarf is located in the constellation Tucana. It is about 900 kiloparsecs (2,900 kly) away, on the opposite side of the Milky Way galaxy to most of the other Local Group galaxies and is therefore important for understanding the kinematics and formation history of the Local Group, as well as the
Maffei 2 is an intermediate spiral galaxy about 10 million light-years away in the constellation Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. Maffei 2 lies in the Zone of Avoidance and is about 99.5% obscured by the Milky Way's foreground dust clouds, and as a result is barely detectable at optical wavelengths. It had been suggested soon after its discovery that Maffei 2 may be a member of the Local Group, but it is now thought to be a member of another nearby group, the IC 342/Maffei Group, the group of galaxies that is the closest to the Local Group .
Messier 74 (also known as NGC 628) is a face-on spiral galaxy in the constellation Pisces. It is at a distance of about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a Grand Design Spiral Galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. However, the relatively large angular size of the galaxy and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 is home to about 100 billion stars.
M74 was discovered by Pierre Méchain in 1780. Méchain then communicated his discovery to Charles Messier, who listed the galaxy in his catalog.
Two supernovae have been identified in M74: SN 2002ap and SN 2003gd.
SN 2002ap has attracted considerable attention because it is one of the few Type Ic supernovae (or hypernovae) observed within 10 Mpc in recent years. This supernovae has been used to test theories on the origins of similar Type Ic supernovae at higher distances and theories on the connection between
NGC 1 is a spiral galaxy located 190 million light-years away in the constellation Pegasus. At about 90,000 light-years in diameter, it is just a little smaller than our galaxy, the Milky Way. It is the first object listed in the New General Catalogue. In the coordinates used at the time of the catalog's compilation (epoch 1860), this object had the lowest right ascension of all the objects in the catalog, making it the first object to be listed when the objects were arranged by right ascension. Since then, the coordinates have shifted, and this object no longer has the lowest right ascension of all the NGC objects.
NGC 1365, also known as the Great Barred Spiral Galaxy, is a barred spiral galaxy about 56 million light-years away in the constellation Fornax. The core is an oval shape with an apparent size of about 50″ × 40″. The spiral arms extend in a wide curve north and south from the ends of the east-west bar and form an almost ring like Z-shaped halo.
Supernovae 2001du, 1983V, and 1957C were observed in NGC 1365.
NGC 2442 / 2443 is an intermediate spiral galaxy about 50 million light-years away in the constellation Volans. It was discovered by Sir John Herschel. Associated with this galaxy is HIPASS J0731-69, a cloud of gas devoid of any stars. It is likely that the cloud was torn loose from NGC 2442 by a companion.
NGC 4261 is an elliptical galaxy located behind the Virgo Cluster in the W-cloud.
The active galactic nucleus (AGN) contains a 400 million solar mass supermassive black hole (SMBH) with a 800 light-year-wide spiral-shaped disk of dust fueling it.
The galaxy is estimated to be about 60 thousand light-years across, and the jet is estimated to span about 88 thousand light-years.
NGC 4314 is a barred spiral galaxy approximately 40 million light-years away in the constellation Coma Berenices. Perhaps the most prominent and unusual feature is its "nuclear starbust ring" of bright young stars. These rings are thought to be due in part to Lindblad resonance. It is thought that this explosion of star formation has occurred over the past few millions of years. This time frame is remarkably short in astronomical terms because most main sequence stars have lifetimes of billions of years and their birth is not usually uniform throughout a galaxy. Further study will be required to understand more about the evolution of such ring structures in galaxies.
The Virgo Stellar Stream, also known as Virgo Overdensity, is the proposed name for a stellar stream in the constellation of Virgo which was discovered in 2005. The stream is thought to be the remains of a dwarf spheroidal galaxy that is in the process of merging with the Milky Way. It is the largest galaxy visible from the Earth, in terms of the area of the night sky covered.
The stream was discovered from photometric data from the Sloan Digital Sky Survey, which was used to create a three dimensional map of the Milky Way, using the colors and brightness of certain characteristic types of stars to estimate their distance (a method known as "photometric parallax"). The first suggestion of a new galaxy in Virgo was made in 2001 from data obtained as part of the QUEST survey, which used the 1.0 metre Schmidt telescope at the Llano del Hato National Astronomical Observatory in Venezuela to look for RR Lyrae variable stars. Five were found in a clump with a right ascension near 12.4 hours, and the astronomers speculated that this clump was part of a small galaxy being "cannibalised" by the Milky Way.
The stream covers over 100 square degrees, and possibly as much as 1,000 square
I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away. The galaxy was first identified by Swiss astronomer Fritz Zwicky in a 1930s photographic survey of galaxies. Studies at the Palomar Observatory some 40 years ago led astronomers to believe that the galaxy erupted with star formation billions of years after its galactic neighbors. Galaxies resembling I Zwicky 18's youthful appearance are typically found only in the early universe. The Hubble Space Telescope, however, found faint, older stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.
Spectroscopic observations with ground-based telescopes have shown that I Zwicky 18 is almost exclusively composed of hydrogen and helium, the main ingredients created in the Big Bang. The galaxy's primordial makeup suggests that its rate of star formation has been much lower than that of other galaxies of similar age. The galaxy has been studied with most of NASA's telescopes, including the Spitzer Space Telescope, the Chandra X-ray
Messier 99 (also known as M99 or NGC 4254) is an unbarred spiral galaxy approximately 50 million light-years away in the constellation Coma Berenices.
The galaxy has a normal looking arm and an extended arm that is less tightly wound. A bridge of neutral hydrogen gas links NGC 4254 with VIRGOHI21. The gravity from the possible dark galaxy VIRGOHI21 may have distorted M99 and drawn out the gas bridge, as the two galaxy-sized objects have a close encounter, before they go their separate ways. It is expected that the drawn out arm will relax to match the normal arm once the encounter is over. Three supernovae have been observed in this galaxy.
Messier 99 was discovered by Pierre Méchain on March 17, 1781 along . The discovery was then reported to Charles Messier, who included the object in the Messier Catalogue, which was the first astronomical catalogue of star clusters, nebulae, and galaxies.
Messier 99 was one of the first galaxies in which a spiral pattern was first seen. The spiral pattern was first identified by Lord Rosse in the spring of 1846.
The Wolf-Lundmark-Melotte (WLM) galaxy is an irregular galaxy discovered in 1909 by Max Wolf, and is located on the outer edges of the local group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.
In 1994, A. E. Dolphin used the Hubble Space Telescope to create a color-magnitude diagram for WLM. It showed that around half of all the star formation in this galaxy occurred during a burst that started ~13 Gyr ago. During the burst, the metallicity of WLM rose from [Fe/H] ~ -2.2 to [Fe/H] -1.3. There being no horizontal-branch population, Dolphin concludes that no more than ~20 M☉ per Myr of star formation occurred in the period from 12 to 15 Gyr ago. From 2.5 to 9 Gyr ago, the mean rate of star formation was 100 to 200 M☉ per Myr.
WLM has one known globular cluster that Hodge et al. (1999) determined has Mv = -8.8 and [Fe/H] = -1.5 with an age of ~15 Gyr. This cluster has a luminosity that is slightly over the average for all globulars. The seeming lack of faint low-mass globular clusters can not be explained by the weak tidal forces of the WLM system.
In E.E. Smith’s Lensman novels, the
IC 1101 is a supergiant elliptical galaxy at the center of the Abell 2029 galaxy cluster. It is 1.07 billion light years away in the constellation of Serpens and is classified as a cD class of galaxy.
The galaxy has a diameter of approximately 6 million light years, which makes it currently (as of 2012) the largest known galaxy in terms of breadth. It is the central galaxy of a massive cluster containing a mass (mostly dark matter) of roughly 100 trillion stars. Being more than 50 times the size of the Milky Way and 2000 times as massive, if it were in place of our galaxy, it would swallow up the Large Magellanic Cloud, Small Magellanic Cloud, Andromeda Galaxy, and Triangulum Galaxy. IC 1101 owes its size to many collisions of much smaller galaxies about the size of the Milky Way and Andromeda galaxies.
NGC 4676, or the Mice Galaxies, are two spiral galaxies in the constellation Coma Berenices. About 290 million light-years away, they are presently in the process of colliding and merging. Their name refers to the long tails produced by tidal action—the relative difference between gravitational pulls on the near and far parts of each galaxy—known here as a galactic tide. Members of the Coma cluster, it is a possibility that both galaxies have experienced collision, and will continue colliding until they coalesce.
The colors of the galaxy are peculiar. In the upper galaxy (NGC 4676A, to the right in the photo), a core with some dark markings is surrounded by a bluish white remnant of spiral arms. The tail is unusual, starting out blue and terminating in a more yellowish color, despite the fact that the beginning of each arm in virtually every spiral galaxy starts yellow and terminates in a bluish color. The lower galaxy (NGC 4676B, to the left) is closer to normal, with a yellowish core and two arcs; arm remnants underneath are bluish as well.
The galaxies were photographed in 2002 by the Hubble Space Telescope.
NGC 3077 is a smaller member of the M81 Group. It looks much like an elliptical galaxy. However, it is peculiar for two reasons. First, it shows wispy edges and scattered dust clouds that are probably a result of gravitational interaction with its larger neighbors, similar to the galaxy M82. Second, this galaxy has an active nucleus. This caused Carl Seyfert in 1943 to include it in his list of galaxies, which are now called Seyfert Galaxies. However, NGC 3077, though an emission line galaxy, is today no longer classified as a Seyfert galaxy.
NGC 3077 was discovered by William Herschel on November 8, 1801. He remarked that "On the nF (NE) side, there is a faint ray interrupting the roundness." Admiral Smyth described it as "A bright-class round nebula; it is a lucid white, and lights up in the centre ... between these [stars,] the sky is intensely black, and shows the nebula as if floating in awful and illimitable space, at an inconceivable distance."
At least two techniques have been used to measure distances to NGC 3077. The surface brightness fluctuations (SBF) distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of
NGC 3184 is a spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. It has two HII regions named NGC 3180 and NGC 3181.
NGC 3184 is notable for its high abundance of heavy elements and (SN 1999gi) that was a magnitude 14 Type II supernova detected on December 9, 1999. Other supernovae in NGC 3184 include 1921B (mag 13.5), 1921C (mag 11) and 1937F (mag 13.5).
On May 31, 2010, Koichi Itagaki detected a magnitude 17 optical transient 33" east and 61" north of the center of NGC 3184 at coordinates 10 18 19.89 +41 26 28.8. This event may be an outbursting Luminous blue variable (LBV) star. Archival Hubble and Spitzer images of NGC 3184 seem to show no progenitor for optical transient SN 2010dn. SN 2010dn is just like SN 2008S and NGC 300-OT. On day 2, SN 2010dn had an unfiltered magnitude of 17.1, corresponding to a peak absolute magnitude of roughly -13.3.
NGC 772 (also known as Arp 78) is an unbarred spiral galaxy approximately 130 million light-years away in the constellation Aries. It is notable for possessing a single elongated outer spiral arm, which has likely arisen due to tidal interactions with nearby galaxies. At around 100,000 light years in diameter, NGC 772 rivals the Milky Way Galaxy in size and is surrounded by several satellite galaxies including the dwarf elliptical, NGC 770. Two supernovae (SN 2003 hl & SN 2003 iq) have been observed in NGC 772.
It probably has a H II nucleus, however it may be a transitional object.
NGC 7752 and NGC 7753 are a set of galaxies approximately 272 million light-years away in the constellation Pegasus.
NGC 7753 is the primary galaxy. It is a barred spiral galaxy with a small nucleus. NGC 7752 is the satellite galaxy of NGC 7753. It is a barred lenticular galaxy that is apparently attached to one of NGC 7753's spiral arms, it would resemble the Whirlpool Galaxy (M51A) and its satellite NGC 5195 (M51B). On January 2, 2006, a supernova (SN 2006A) was observed in NGC 7753. It was the only supernova observed in the NGC 7752 and NGC 7753 galaxies (so far).
The Draco Dwarf is a spheroidal galaxy which was discovered by Albert George Wilson of Lowell Observatory in 1954 on photographic plates of the National Geographic Society's Palomar Observatory Sky Survey (POSS). It is part of the local group and a satellite galaxy of the Milky Way galaxy. The Draco Dwarf is situated in the direction of the Draco Constellation at 34.6° above the galactic plane.
Paul W. Hodge analyzed the distribution of its stars in 1964 and concluded that its ellipticity was 0.29 ± 0.04. Recent studies have indicated that the galaxy may potentially hold large amounts of dark matter. Having an absolute magnitude of -8.6 and a total luminosity of only 2×10 L☉, it is one of the faintest companions to our Milky Way.
Draco Dwarf contains many red giant branch (RGB) stars; five carbon stars have been identified in Draco Dwarf and four likely asymptotic giant branch (AGB) stars have been detected.
The Draco Dwarf is estimated to be about 80 ± 10 kpc from earth and span a distance of 830 ± 100 × 570 ± 70 pc.
In 1961, Walter Baade and Henrietta H. Swope studied Draco Dwarf and discovered over 260 variables, of the 138 in the cluster's center, all but five were determined
GRB 990123 is a gamma-ray burst that occurred on January 23, 1999. It was the first GRB for which a simultaneous optical flash was detected. GRB 990123 is one of the most distant distinct landmarks in our map of the universe.
Astronomers first managed to obtain a visible-light image of a GRB as it occurred on January 23, 1999, using the ROTSE-I telescope in Los Alamos, New Mexico. The ROTSE-I was operated by a team under Dr. Carl Akerlof of the University of Michigan and included members from Los Alamos National Laboratory and Lawrence Livermore National Laboratory. The robotic telescope was fully automated, responding to signals from NASA's BATSE instrument aboard the Compton Gamma Ray Observatory within seconds, without human intervention. In the dark hours of the morning of January 23, 1999, the Compton satellite recorded a gamma-ray burst that lasted for about a minute and a half. There was a peak of gamma and X-ray emission 25 seconds after the event was first detected, followed by a somewhat smaller peak 40 seconds after the beginning of the event. The emission then fizzled out in a series of small peaks over the next 50 seconds, and eight minutes after the event had faded to
Messier 66 (also known as NGC 3627) is an intermediate spiral galaxy about 36 million light-years away in the constellation Leo. It was discovered by Charles Messier in 1780. M66 is about 95 thousand light-years across with striking dust lanes and bright star clusters along sweeping spiral arms. M66 is part of the famous Leo Triplet, a small group of galaxies that also includes M65 and NGC 3628.
Gravitational interaction from its past encounter with neighboring NGC 3628 has resulted in:
This third result shows up visually as an extremely prominent and unusual spiral arm and dust lane structures as originally noted in the Atlas of Peculiar Galaxies.
Messier 85 (also known as M85 or NGC 4382 or PGC 40515 or ISD 0135852) is a lenticular galaxy (type S0) in the Coma Berenices constellation. It is 60 million light years away, and it is estimated to be 125,000 light years across.
It was discovered by Pierre Méchain in 1781. It is the northernmost outlier of the Virgo cluster discovered as of 2004.
The type I supernova, 1960R was discovered in M85 on December 20, 1960 and reached an apparent magnitude of 11.7.
M85 is interacting with the nearby spiral galaxy NGC 4394, and a small elliptical galaxy called MCG 3-32-38.
NGC 300 (also known as Caldwell 70) is a spiral galaxy in the constellation Sculptor. It is one of the closest galaxies to the Local Group, and probably lies between us and the Sculptor Group. It is the brightest of the five main spirals in the direction of the Sculptor Group. It is inclined at an angle of 42° when viewed from earth and shares many characteristics of the Triangulum Galaxy.
NGC 300 and the irregular galaxy NGC 55 have traditionally been identified as members of the Sculptor Group, a nearby group of galaxies in the constellation of the same name. However, recent distance measurements indicate that these two galaxies actually lie in the foreground. It is likely that NGC 300 and NGC 55 form a gravitationally bound pair.
In 1986, Allan Sandage estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc). By 1992, this had been updated to 6.9 Mly (2.1 Mpc) by Freedman et al. In 2006, this was revised by Karachentsev et al. to be 7.0±0.3 Mly (2.15±0.10 Mpc). At about the same time, the tip of the red giant branch (TRGB) method was used to produce an estimate of 5.9±0.4 Mly (1.82±0.13 Mpc) using edge detection and 6.1±0.4 Mly (1.87±0.12 Mpc) using maximum likelihood. These
NGC 3115 (also called the Spindle Galaxy or Caldwell 53) is a lenticular (S0) galaxy in the constellation Sextans. The galaxy was discovered by William Herschel on February 22, 1787. At about 32 million light-years away from us it is several times bigger than our Milky Way. It is a lenticular (S0) galaxy because it contains a disk and a central bulge of stars, but without a detectable spiral pattern. NGC 3115 is seen almost exactly edge-on that it was occasionally mis-classified as elliptical. There is some speculation that NGC 3115, in its youth, was a quasar.
NGC 3115 has consumed most of the gas of its youthful accretion disk. It has very little gas and dust left that would trigger new star formation. The vast majority of its component stars are very old.
In 1992 John Kormendy of the University of Hawaii and Douglas Richstone of the University of Michigan announced what was observed to be a supermassive black hole in the galaxy. Based on orbital velocities of the stars in its core, the central black hole has mass measured to be approximately one billion solar masses. The galaxy appears to have mostly old stars and little or no activity. The growth of its black hole has also
NGC 3370 (also known as UGC 5887 or Silverado Galaxy) is a spiral galaxy about 98 million light-years away in the constellation Leo. It is comparable to our own Milky Way both in diameter (100,000 light years) and mass (10 solar masses). NGC 3370 exhibits an intricate spiral arm structure surrounding a poorly defined nucleus.
NGC 3370 was likely discovered by William Herschel, who provided it with the designation II 81. His son John later designated it 750. William Herschel cataloged II 80 to NGC 3348 before and II 82 to NGC 3455 after NGC 3370.
The object has a surface brightness of 13 and a position angle (PA) of 140°.
On November 14, 1994, S. Van Dyk and the Leuschner Observatory Supernova Search discovered a supernova in NGC 3370 at 10 44 21.52 +17° 32′ 20.7′′, designated SN 1994ae. SN 1994ae was a type Ia supernova, and one of the nearest and best observed since the advent of modern digital detectors. The maximal light of the supernova was estimated to have occurred between November 30 and December 1, peaking at visual magnitude 13.
NGC 4567 and NGC 4568 (nicknamed the Siamese Twins or the Butterfly Galaxies) are a set of spiral galaxies about 60 million light-years away in the constellation Virgo. They were both discovered by William Herschel in 1784. They are part of the Virgo cluster of galaxies. Only one supernova (SN 2004cc) was observed in the Siamese Twins.
These galaxies may be in the process of colliding and merging with each other. They were named "Siamese Twins" because they look like they're connected.
NGC 47 (also known as NGC 58, MCG -1-1-55, IRAS00119-0726 and PGC 967) is a barred spiral galaxy in the constellation Cetus, discovered in 1886 by Ernst Wilhelm Leberecht Tempel. Its alternate name NGC 58 is due to the observation by Lewis Swift, who was unaware that Tempel had already discovered the object earlier. It appears as a small, faint spiral nebula with a bright core and is slightly oval.
It is approximately 236 million light years from Earth, measured by way of a generic "redshift estimate".
NGC 5408 is an irregular galaxy in the constellation Centaurus. The galaxy was discovered by John Frederick William Herschel in 1834.
NGC 5408 is located near the M83 Subgroup of the Centaurus A/M83 Group, a relatively nearby group of galaxies. However, it is unclear as to whether NGC 5408 is part of the group.
NGC 7318 (also known as UGC 12099/UGC 12100 or HCG 92d/b) are a pair of colliding galaxies about 300 million light-years away in the Constellation Pegasus. They are members of the famous Stephan's Quintet.
The Spitzer Space Telescope revealed the presence of a huge intergalactic shock wave, shown by the magnificent green arc in the picture at right produced by one galaxy falling into another at millions of miles per hour. As NGC 7318B collides with NGC 7318A, gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow. The molecular hydrogen seen here is one of the most turbulent forms of molecular hydrogen ever seen. This phenomenon was discovered by an international team of scientists of the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg. Most notable is the fact that this collision can help provide a view into what happened in the early universe 10 billion years ago when it formed.
The Boötes Dwarf Galaxy (Boo I dSph) is a faint galaxy, with a luminosity of 100,000 L☉ and an absolute magnitude of –5.8. It lies about 197 kilolight-years (60.4 kiloparsecs) away in the constellation Boötes. This dwarf spheroidal galaxy appears to be tidally disrupted by the Milky Way Galaxy, which it orbits, and has two stellar tails that cross over to form a cross. Tidally disrupted galaxies usually only form one tail.
Like many of the ultrafaint dwarf spheroidals, the entire galaxy is fainter than the star Rigel (absolute magnitude –6.8).
The Large Magellanic Cloud (LMC) is a nearby irregular galaxy, and a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs (≈160,000 light-years), the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal (~ 16 kiloparsecs) and Canis Major Dwarf Galaxy (~ 12.9 kiloparsecs) lying closer to the center of the Milky Way. It has a mass equivalent to approximately 10 billion times the mass of our Sun (10 solar masses), making it roughly 1/100 as massive as the Milky Way, and a diameter of about 14,000 light-years (~ 4.3 kpc). The LMC is the fourth largest galaxy in the Local Group, after the Andromeda Galaxy (M31), our own Milky Way Galaxy, and the Triangulum Galaxy (M33).
While the LMC is often considered an irregular type galaxy (the NASA Extragalactic Database lists the Hubble sequence type as Irr/SB(s)m), the LMC contains a very prominent bar in its center, suggesting that it may have previously been a barred spiral galaxy. The LMC's irregular appearance is possibly the result of tidal interactions with both the Milky Way and the Small Magellanic Cloud (SMC).
It is visible as a faint "cloud" in the night sky of the southern
NGC 1316 (also known as Fornax A) is a lenticular galaxy about 70 million light-years away in the constellation Fornax. NGC 1316 is a radio galaxy. It is the fourth-brightest radio source in the sky (as seen at 1400 MHz).
François Schweizer studied NGC 1316 extensively in the late 1970s. He found that the galaxy appeared to look like a small elliptical galaxy with some unusual dust lanes embedded within a much larger envelope of stars. The outer envelope contained many ripples, loops, and arcs. He also identified the presence of a compact disk of gas near the center that appeared inclined relative to the stars and that appeared to rotate faster than the stars. Based on these results, Schweizer suggested that NGC 1316 was built up through the merger of several smaller galaxies. These merger events may have fueled the central supermassive black hole with gas, causing the galaxy to become a radio galaxy. He also states that NGC 1316 is comparable to the giant elliptical galaxies found in the centers of other clusters of galaxies. Using spectroscopy of its brightest globular clusters, the merger is estimated to have occurred ~3 Gyr ago.
NGC 1316 is located within the Fornax Cluster, a
NGC 3310 is a grand design spiral galaxy in the constellation Ursa Major. It is a starburst galaxy and its likely that NGC 3310 collided with one of its satellite galaxies about 100 million years ago, triggering widespread star formation. It is thought to be located approximately 46 million light-years away from the Earth, and is thought to be about 22000 light-years wide.
The ring clusters of NGC 3310 have been undergoing starburst activity for at least the last 40 Myr.
NGC 3628 is an unbarred spiral galaxy about 35 million light-years away in the constellation Leo. It was discovered by William Herschel in 1784. It has an approximately 300,000 light-years long tidal tail. NGC 3628 along with M65 and M66 form the famous Leo Triplet, a small group of galaxies. Its most conspicuous feature is the broad and obscuring band of dust located along the outer edge of its spiral arms, effectively transecting the galaxy to our view.
3C 279 (also known as 4C–05.55, NRAO 413, and PKS 1253–05) is an optically violent variable quasar (OVV), which is known in the astronomical community for its variations in the visible, radio, and x-ray bands. The quasar was observed to have undergone a period of extreme activity from 1987 until 1991. The Rosemary Hill Observatory (RHO) started observing 3C 279 in 1971, and was further observed by the Compton Gamma Ray Observatory in 1991, when it was unexpectedly discovered to be one of the brightest gamma ray objects in the sky. Superluminal motion was detected during observations first made in 1973, in a jet of material departing from the quasar.
The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc (4.3 Mly) from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy, NGC 3109.
Antlia Dwarf was first cataloged in 1985 by H. Corwin, Gérard de Vaucouleurs, and A. de Vaucouleurs. Later in 1985 and 1987 it was noted as a possible nearby dwarf galaxy by two groups of astronomers. It was finally confirmed as a dwarf galaxy in 1997 by Alan Whiting, Mike Irwin and George Hau during a survey of the northern sky. They for the first time resolved it into stars and determined the distance to it—1.15 Mpc (the modern distance estimate is slightly larger).
In 1999 Antlia Dwarf was identified by Sidney van den Bergh as the fourth member of the Antlia Group—the group of galaxies closest to the Local Group.
The Antlia Dwarf is classified alternatively as a dwarf elliptical galaxy of type dE3.5, or either as a dwarf spheroidal galaxy (dSph) or as a
Leo I is a dwarf spheroidal galaxy in the constellation Leo. At about 820,000 light-years distant, it is a member of the Local Group of galaxies and is thought to be one of the most distant satellites of the Milky Way galaxy. It was discovered in 1950 by Albert George Wilson on photographic plates of the National Geographic Society - Palomar Observatory Sky Survey, which were taken with the 48-inch Schmidt camera at Palomar Observatory.
The measurement of radial velocities of some bright red giants in Leo I have made possible to measure its mass. It was found to be at least (2.0 ± 1.0) × 10 MSun. The results are not conclusive, and do not deny or confirm the existence of a large dark matter halo around the galaxy. However, it seems to be certain that the galaxy does not rotate.
It has been suggested that Leo I is a tidal debris stream in the outer halo of the Milky Way. This hypothesis has not been confirmed, however.
Typical to a dwarf galaxy, the metallicity of Leo I is very low, only one percent that of the Sun. Gallart et al. (1999) deduce from Hubble Space Telescope observations that the galaxy experienced a major increase (accounting for 70% to 80% of its population) in its
NGC 1566 is an intermediate spiral galaxy in the constellation Dorado. It is the dominant member of the Dorado Group and also its brightest member. It is the second brightest Seyfert galaxy after NGC 1068. Its absolute luminosity is 3.7×10 L☉. It contains 1.4×10 M☉ of H I.
On June 19, 2010, Berto Monard from South Africa detected a magnitude 16 supernova 13" west and 22" south of the center of NGC 1566 at coordinates 04 19 58.83 -54 56 38.5.
NGC 6946, (also known as the Fireworks Galaxy, Arp 29, and Caldwell 12), is an intermediate spiral galaxy about 65 million light-years away, in the constellations Cepheus and Cygnus. It was discovered by William Herschel on September 9, 1798. NGC 6946 is highly obscured by interstellar matter of the Milky Way galaxy, as it is quite close to the galactic plane. Nine supernovae (SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, and SN 2008S) have been observed in NGC 6946.
There is polarisation data within ranges 0.17-0.18 m and 0.21-0.23 m, observed in 2003 by WSRT.
Atlas of the Universe
NGC 7742 is a face-on unbarred spiral galaxy in the constellation Pegasus.
The galaxy is unusual in that it contains a ring but no bar. Typically, bars are needed to produce a ring structure. The bars' gravitational forces move gas to the ends of the bars, where it forms into the rings seen in many barred spiral galaxies. In this galaxy, however, no bar is present, so this mechanism cannot be used to explain the formation of the ring. O. K. Sil'chenko and A. V. Moiseev proposed that the ring was formed partly as the result of a merger event in which a smaller gas-rich dwarf galaxy collided with NGC 7742. As evidence for this, they point to the unusually bright central region, the presence of highly-inclined central gas disk, and the presence of gas that is counterrotating (or rotating in the opposite direction) with respect to the stars.
The Tadpole Galaxy is a disrupted barred spiral galaxy located 400 million light years from Earth toward the northern constellation Draco. Its most dramatic features are a trail of stars about 280 thousand light-years long and massive, bright blue star clusters.
It is hypothesized that a more compact intruder galaxy crossed in front of the Tadpole Galaxy—from left to right from the perspective of Earth—and was slung around behind the Tadpole by their mutual gravitational attraction. During this close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust, forming the conspicuous tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.
Messier 110 (also known as M110 and NGC 205) is a dwarf spheroidal galaxy that is a satellite of the Andromeda Galaxy. M110 contains some dust and hints of recent star formation, which is unusual for dwarf elliptical galaxies in general.
Although Charles Messier never included the galaxy in his famous list, it was depicted by him, together with M32, on a drawing of the Andromeda galaxy; a label on the drawing indicates that Messier first observed NGC 205 on August 10, 1773. The galaxy was independently discovered by Caroline Herschel on August 27, 1783; her brother William Herschel described her discovery in 1785. The suggestion to assign the galaxy a Messier number was made by Kenneth Glyn Jones in 1967.
In 1999, Johnson and Modjaz discovered a nova in M110.
Unlike M32, NGC205 does not show evidence for a supermassive black hole at its center.
NGC 3982 is an intermediate spiral galaxy approximately 68 million light-years away in the constellation Ursa Major. It is also known as UGC 6918. It was discovered by William Herschel on April 14, 1789 and misclassified as planetary nebula. NGC 3982 is a part of the M109 Group.
At an apparent magnitude of 12.0, NGC 3982 needs a telescope to be viewed. Using small telescopes, the galaxy appears as a very faint, diffuse patch of light with its central region appearing as a slightly brighter diffuse ball.
NGC 3982 is a Seyfert 2 galaxy that spans about 30,000 light-years, about one-third of the size of our Milky Way galaxy. The galaxy is receding from us at about 1109 km/s. The galaxy is a typical spiral galaxy, similar to our Milky Way. It harbors a supermassive black hole at its core and has massive regions of star formation in the bright blue knots in the spiral arms. Supernovae are likely to be found within these regions.
NGC 3982 has a high rate of star birth within its arms, which are lined by pink star-forming regions of glowing hydrogen and newborn blue star clusters. Its bright nucleus is home to older populations of stars, which grow more densely packed toward the center.
Andromeda I is a dwarf spheroidal galaxy(dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.
Andromeda I was discovered by Sidney van den Bergh in 1970 with the Mount Palomar Observatory 48-inch telescope. Further study of Andromeda I was done by the WFPC2 camera of the Hubble Space Telescope. This found that the horizontal branch stars, like other dwarf spheroidal galaxies were predominantly red. From this, and the abundance of blue horizontal branch stars, along with 99 RR Lyrae stars detected in 2005, lead to the conclusion there was an extended epoch of star formation. The estimated age is approximately 10 Gyr. The Hubble telescope also found a globular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.
NGC 1128 is a "dumbbell galaxy" in the Abell 400 galaxy cluster. It is the center of the 3C75 radio source and contains two orbiting supermassive black holes that may be merging. Computer simulations indicate that these two black holes will gradually spiral in toward each other until they merge. Lewis Swift is credited with the discovery of NGC 1128 in 1886. However, there is a possible 5 min error in Swift's records that casts some doubt on his discovery.
NGC 1559 is a barred spiral galaxy in the constellation Reticulum. It is also a Seyfert galaxy. In 2005, a supernova (SN 2005df) was observed. Two other supernovae discovered in NGC 1559 were SN 1984J and SN 1986L. Although it was originally thought to be a member of the Dorado Group, subsequent observations have shown that it is in fact not a member of any galaxy group or cluster and does not have any nearby companions. NGC 1559 has massive spiral arms and strong star formation. It contains a small bar which is oriented nearly east-west and spans 40″. Its bar and disc are the source of very strong radio emissions.
NGC 2403 (also Caldwell 7) is an intermediate spiral galaxy in the constellation Camelopardalis. NGC 2403 is an outlying member of the M81 Group, and is approximately 8 million light-years distant. It bears a striking similarity to M33, being about 50,000 light years in diameter and containing numerous star-forming H II regions. The northern spiral arm connects it to nearby galaxy NGC 2404. NGC 2403 can be observed using 10×50 binoculars.
As of late 2004, there had been two reported supernovae in the galaxy: SN 1954J, which attained a magnitude of 16 at its brightest, and SN 2004dj.
NGC 2403 was discovered by William Herschel in 1788. Allan Sandage detected Cepheid variables in NGC 2403 using the Hale telescope, giving it the distinction of being the first galaxy beyond our local group within which a Cepheid was discovered. He derived a distance of a mere 8 thousand light years. Today, it is thought to be a thousand times further away at about 8 million light years (2.5 Mpc).
NGC 4013 is an edge-on barred spiral galaxy about 55 million light-years away in the constellation Ursa Major. The disk of NGC 4013 shows a distinct "peanut"-shaped bulge in long exposure photographs that N-body computer simulations suggest is consistent with a stellar bar seen perpendicular to the line of sight.
A recent deep color image of NGC 4013 revealed a looping tidal stream of stars extending over 80 thousand light-years from the Galactic Center. This structure is thought to be the remnants of a smaller galaxy that was torn apart by tidal forces as it collided with NGC 4013.
Supernova SN 1989Z was discovered on December 30, 1989 at apparent magnitude 12.
The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an interacting grand-design spiral galaxy in the constellation Canes Venatici. Recently it was estimated to be 23 ± 4 million light-years from the Milky Way Galaxy, but different methods yield distances between 15 and 35 million ly. Messier 51 is one of the best known galaxies in the sky. The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.
What was later known as the Whirlpool Galaxy was discovered on October 13, 1773 by Charles Messier, and is designated as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain. It was however not until 1845 that the Whirlpool became the first to be recognized as a spiral. This was achieved by Lord Rosse employing a 72-inch (~1.83 m) reflecting telescope which he constructed at Birr Castle, Ireland. Sometimes M51 is used to refer to the pair of galaxies, in which
ESO 269-57 (also known as LEDA 45683) is a barred spiral galaxy approximately 155 million light-years away in the constellation Centaurus. It is a member of a well-known cluster of galaxies seen in this direction. The galaxy received this designation when it was catalogued during the first European Southern Observatory (ESO) Survey of the Southern Sky in the 1970s.
In April 1999, the European Southern Observatory (ESO) took a look at ESO 269-57 and shows the complex structure of it, with an inner "ring", of several tightly wound spiral arms, surrounded by two outer ones that appear to split into several branches. Many blue and diffuse objects are visible - most are star-forming regions. The velocity is just over 3100 km/s, indicating the distance. It extends over about 4 arcmin in the sky, corresponding to nearly 200,000 light-years across.
Messier 32 (also known as NGC 221 and Le Gentil) is a dwarf elliptical galaxy about 2.65 million light-years away in the constellation Andromeda. M32 is a satellite galaxy of the famous Andromeda Galaxy (M31) and was discovered by Le Gentil in 1749. M32 measures only 6.5 ± 0.2 kly in diameter at the widest point. Like most elliptical galaxies, M32 contains mostly older faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the relatively recent past.
The structure and stellar content of M32 is difficult to explain by traditional galaxy formation models. Recent simulations suggest a new scenario in which the strong tidal field of M31 can transform a spiral galaxy into a compact elliptical. As a small spiral galaxy falls into the central parts of M31, most of the outer layers of the smaller spiral are stripped away. The central bulge of the galaxy is much less affected and retains its morphology. Tidal effects trigger a massive star burst in the core, resulting in the high density of M32 we observe today. There is also evidence that M32 has an outer disk.
At least two techniques have
Messier 77 (also known as NGC 1068) is a barred spiral galaxy about 47 million light-years away in the constellation Cetus. Messier 77 is an active galaxy with an Active Galactic Nucleus (AGN), which is obscured from view by astronomical dust at visible wavelengths. The diameter of the molecular disk and hot plasma associated with the obscuring material was first measured at radio wavelengths by the VLBA and VLA. The hot dust around the nucleus was subsequently measured in the mid-infrared by the MIDI instrument at the VLTI. It is the brightest Seyfert galaxy and is of type 2.
Messier 77's diameter is 170,000 light-years.
Messier 77 was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his catalog. Both Messier and William Herschel described this galaxy as a star cluster. Today, however, the object is known to be a galaxy.
X-ray source 1H 0244+001 in Cetus has been identified as Messier 77 (NGC 1068, M77).
Messier 91 (also known as NGC 4548 or M91) is a barred spiral galaxy located in the Coma Berenices constellation and is part of the Virgo Cluster of galaxies. M91 is about 63 million light-years away from the earth. It was the last of a group of eight nebulae discovered by Charles Messier in 1781. Originally M91 was a missing Messier object in the catalogue as the result a bookkeeping mistake by Messier. It was not until 1969 that amateur astronomer William C. Williams realized that M91 was NGC 4548, which was documented by William Herschel in 1784.
Messier 91 was discovered on the night of March 18, 1781, Charles Messier described it as Nebula without stars, fainter than M90. Messier mistakenly logged its position from Messier 58, where in fact it should have been Messier 89. William Herschel observed the same galaxy on April 8, 1784. Williams solved the missing Messier object by measuring its right ascension and declination relative to those of the nearby galaxy M89 (there are no suitable reference stars in the vicinity). Williams applied the observed differences of M91 with M58, a 9th-magnitude galaxy which Messier recorded in 1778. The calculation reproduces the Messier
Messier 95 (also known as M95 or NGC 3351) is a barred spiral galaxy about 38 million light-years away in the constellation Leo. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier four days later. On 16 March 2012, a supernova was discovered in M95.
The center of the galaxy contains a ring-shaped circumnuclear star-forming region with a diameter of approximately 2000 ly (600 pc).
M95 is one of several galaxies within the M96 Group, a group of galaxies in the constellation Leo. The group also includes the Messier objects M96 and M105.
A Type II supernova, designated as SN 2012aw, was discovered in M95 on 16 March 2012.
NGC 3079 is a barred spiral galaxy about 50 million light-years away, and located in the constellation Ursa Major. A prominent feature of this galaxy is the "bubble" forming in the very center (see picture at right).
The bubble forming in the center of NGC 3079 is believed to be about 3000 light-years wide and to rise more than 3500 light-years above the disc of the galaxy. It is speculated that the bubble is being formed by particles streaming at high speeds, which were in turn caused by a large burst of star formation. This current bubble is thought to have been created about one million years ago, and computer modeling suggests that there is an ongoing cycle of forming bubbles, with a new bubble forming approximately every 10 million years.
NGC 3953 is a barred spiral galaxy located in the constellation Ursa Major.
Two supernovae have been identified within NGC 3953: the type Ia supernova SN 2001dp and SN 2006bp.
NGC 3953 is a member of the M109 Group, a large group of galaxies located within the constellation Ursa Major that may contain over 50 galaxies.
NGC 7331 (also known as Caldwell 30) is a spiral galaxy about 40 megalight-years (12 Mpc) away in the constellation Pegasus. It was discovered by William Herschel in 1784. NGC 7331 is the brightest member of the NGC 7331 Group of galaxies.
The galaxy is similar in size and structure to the galaxy we inhabit, and is often referred to as "the Milky Way's twin", although recent discoveries regarding the structure of the Milky Way may call this similarity into doubt.
In spiral galaxies the central bulge typically co-rotates with the disk but the bulge in the galaxy NGC 7331 is rotating in the opposite direction to the rest of the disk. The current bulge may have formed from infalling material, however if it has been there since the formation of the galaxy then it would be difficult to explain how such a situation arose.
SN 1959D, a Type IIL supernova, is the only supernova that has been identified within NGC 7331. The supernova was discovered by Milton Humason and H. S. Gates in a survey at Palomar Observatory.
The Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years (six megaparsecs) away in the constellation Ursa Major, first discovered by Pierre Méchain on March 27, 1781, and communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the ESA released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed from 51 individual exposures, plus some extra ground-based photos.
On August 24, 2011, a Type Ia supernova, SN 2011fe, was discovered in M101.
Pierre Méchain, the discoverer of Messier 101, described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires."
William Herschel noted in 1784 that "[M101] in my 7, 10, and 20-feet [focal length] reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will,
Messier 83 (also known as the Southern Pinwheel Galaxy, M83 or NGC 5236) is a barred spiral galaxy approximately 15 million light-years away in the constellation Hydra. It is one of the closest and brightest barred spiral galaxies in the sky, making it visible with binoculars. Six supernovae (SN 1923A, SN 1945B, SN 1950B, SN 1957D, SN 1968L and SN 1983N) have been observed in M83.
Nicolas Louis de Lacaille discovered M83 on February 23rd, 1752 at the Cape of Good Hope. Charles Messier added it to his catalogue of nebulous objects (now known as the Messier Catalogue) in March 1781.
On 16 June 2008 NASA's Galaxy Evolution Explorer project reported finding large numbers of new stars in the outer reaches of the galaxy. It had hitherto been thought that these areas lacked the materials necessary for star formation.
M83 is at the center of one of two subgroups within the Centaurus A/M83 Group, a nearby group of galaxies. Centaurus A is at the center of the other subgroup. These two groups are sometimes identified as one group and sometimes identified as two groups. However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups
The Triangulum Galaxy is a spiral galaxy approximately 3 million light years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598, and is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, which includes the Milky Way Galaxy, the Andromeda Galaxy and about 30 other smaller galaxies. It is one of the most distant permanent objects that can be viewed with the naked eye.
Under exceptionally good viewing conditions with no light pollution, the Triangulum Galaxy can be seen with the naked eye. It is one of the most distant permanent objects that can be viewed without the aid of a telescope. Being a diffuse object, its visibility is strongly affected by small amounts of light pollution. It ranges from easily visible by direct vision in dark skies to a difficult averted vision object in rural or suburban skies. For this reason, Triangulum is one of the critical sky marks of the Bortle Dark-Sky Scale.
The galaxy is sometimes informally referred to as the "Pinwheel Galaxy" by some amateur astronomy references and in some public
The Ursa Minor Dwarf dwarf elliptical galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. It is part of the Ursa Minor constellation, and a satellite galaxy to the Milky Way. The galaxy consists mainly of older stars and there appears to be little to no ongoing star formation in the Ursa Minor Dwarf galaxy.
In 1999, Mighell & Burke used the Hubble Space Telescope to confirm that the UMi system had a straight forward evolutionary history with a single ~2 billion years long burst of star formation around 11 billion years ago.