This article lists some galaxy groups and galaxy clusters.
Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.
Some clusters exhibiting strong evidence of dark matter.
|Bullet Cluster||In this collision between two clusters of galaxies, the stars pass between each other unhindered, while the hot, diffuse gas experiences friction and is left behind between the clusters. The gas dominates the visible mass budget of the clusters, being several times more massive than all the stars. Yet the regions with the stars show more gravitational lensing than the gas region, indicating that they are more massive than the gas. Some dark (since we don't see it), collision-less (or it would have been slowed, like the gas) matter is inferred to be present to account for the extra lensing around otherwise low-mass regions.|
|Abell 520||This is actually a collision between two galaxy clusters. The galaxies and the dark matter seems to have separated out into separate dark and light cores.|
|Abell 2142||A collision between two massive, X-ray luminous galaxy clusters.|
| Cl 0024+17 |
(ClG 0024+16, ZwCl 0024+1652)
|This is a recently coalesced merger of galaxy clusters, which has resulted in a ring of dark matter around the galaxies, yet to be redistributed.|
This is a list of galaxy groups and clusters that are well known by something other than an entry in a catalog or list, or a set of coordinates, or a systematic designation.
|Galaxy cluster||Origin of name||Notes|
|Bullet Cluster||The cluster is named for the merger of two clusters colliding like a bullet.||Also has a systematic designation of 1E 0657-56|
|El Gordo||Named for its size, El Gordo ("the fat one") is the biggest cluster found in the distant universe (at its distance and beyond), at the time of discovery in 2011, with a mass of 3 quadrillion suns. The second most massive galaxy cluster next to El Gordo is RCS2 J2327, a galaxy cluster with the mass of 2 quadrillion suns.||Also has a systematic designation of ACT-CL J0102-4915.|
|Musket Ball Cluster||Named in comparison to the Bullet Cluster, as this one is older and slower galaxy cluster merger than the Bullet Cluster.||Also has a systematic designation of DLSCL J0916.2+2951.|
|Pandora's Cluster||Named because the cluster resulted from a collision of clusters, which resulted in many different and strange phenomena.||Also has a catalogue entry of Abell 2744.|
|Galaxy group||Origin of name||Notes|
|Local Group||The galaxy group that includes the Milky Way.|
|Bullet Group||Named in comparison with the Bullet Cluster, being of similar formation, except smaller.||Also has a systematic catalogue name SL2S J08544-0121. As of 2014, it was the lowest mass object that showed separation between the concentrations of dark matter and baryonic matter in the object.|
|Copeland Septet||Discovered by British astronomer Ralph Copeland in 1874.|
|Deer Lick Group||Coined by Tom Lorenzin (author of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing") to honor Deer Lick Gap in the mountains of North Carolina, from which he had especially fine views of the galaxy group.||Also referred to as the NGC 7331 Group, after the brightest member of the group.|
|Leo Triplet||Named for the fact it contains only three galaxies.||This small group of galaxies lies in the constellation Leo.|
|Markarian's Chain||This stretch of galaxies forms part of the Virgo Cluster.|
|Robert's Quartet||It was named by Halton Arp and Barry F. Madore, who compiled A Catalogue of Southern Peculiar Galaxies and Associations in 1987.||This compact group of galaxies lies 160 million light-years away in the Phoenix constellation.|
|Seyfert's Sextet||Named after its discoverer, Carl Seyfert. At the time it appeared to contain six external nebulae. It is also called the NGC 6027 Sextet, after its brightest member.||There are actually only five galaxies in the sextet, and only four galaxies in the compact group. One of the galaxies is an ungravitationally bound background object. The other "galaxy" is instead an extension of the interacting system — a tidal stream caused by the merger. The group is, therefore, more properly called HCG 79; the name refers to the visual collection and not the group. HCG 79 lies 190 million light-years away in the Serpens Caput constellation.|
|Stephan's Quintet (Stephan's Quartet)||Named after its discoverer, Édouard Stephan.||There are actually only four galaxies in the compact group, the other galaxy is a foreground galaxy. The group is therefore more properly called HCG 92, because the name refers to a visual collection and not a group. Thus, the real group is also called Stephan's Quartet.|
|Wild's Triplet||Named after the British-born and Australia-based astronomer Paul Wild (1923–2008), who studied the trio in the early 1950s.|
The major nearby groups and clusters are generally named after the constellation they lie in. Many groups are named after the leading galaxy in the group. This represents an ad hoc systematic naming system.
The Local Group contains the largest number of visible galaxies with the naked eye. However, its galaxies are not visually grouped together in the sky, except for the two Magellanic Clouds. The IC342/Maffei Group, the nearest galaxy group, would be visible by the naked eye if it were not obscured by the stars and dust clouds in the Milky Way's spiral arms.
|Galaxy group||Visible galaxies||Notes|
|Local Group||5||Apart from the Milky Way, only 4 galaxies are visible to the naked eye.|
|Centaurus A/M83 Group||2||The Centaurus A galaxy has been spotted with the naked eye by Stephen James O'Meara and M83 has also reportedly been seen with the naked eye.|
|M81 Group||1||Only Bode's Galaxy (M81, NGC 3031) is visible to the naked eye.|
|Galaxy cluster||Virgo Cluster||1784||Discovered by Charles Messier.|
|Compact group||The four brightest members of Stephan's Quintet||1877||Discovered by Edouard Stephan.|
|Double galaxy||Magellanic Clouds||antiquity|
|Most distant galaxy cluster||CL J1001+0220||redshift z=2.506||Announced August 2016.|
|Nearest galaxy cluster||Virgo Cluster||The Virgo Cluster is at the core of the Virgo Supercluster. The Local Group is a member of the supercluster, but not the cluster.|
|Most distant galaxy group|
|Nearest galaxy group||Local Group||0 distance||This is the galaxy group that our galaxy belongs to.|
|Nearest neighbouring galaxy group||IC 342/Maffei Group|
|Most distant proto-cluster||BoRG-58||z~=8|
|Most distant massive proto-cluster||z66OD||z=6.585||At time of discovery in 2019, the object had 12 members, including Himiko.|
|Least massive galaxy group|
|Most massive galaxy cluster||RX J1347.5-1145||mass= 2.0 ± 0.4 × 1015 MSun|
|Galaxy group||Distance||Redshift (z)||Recession velocity (km/s)||Notes|
|Local Group||-||-||-||Our Galaxy, the Milky Way, belongs to the Local Group.|
|LGG 104 (IC 342/Maffei Group, IC 342 / Maffei 1 Group, IC 342 Maffei 1-2 Group)||0.000868||260||The IC 342/Maffei Group contains two subgroups, the IC 342 subgroup (IC 342 Group) and the Maffei 1 subgroup (Maffei subgroup, Maffei 1 Group, Maffei Group).|
|M81 Group (NGC 3031 Group)||3.5 Mpc (11.4 Mly )||0.001115||334|
|Centaurus A/M83 Group (Centarus A Group, M83 Group)||3.66 Mpc (11.9 Mly )||0.000999||299||The Centaurus A/M83 Group contains two subgroups, the Centaurus A subgroup (Centaurus A Group, NGC 5128 Group, LGG 344) and the M83 subgroup (M83 Group, NGC 5236 Group, LGG 355).|
|Sculptor Group (South Polar Group)||3.9 Mpc (12.7 Mly )|
|Canes Venatici Group (Canes Venatici I Group, Canes I Group, M94 Group, NGC 4736 Group, LGG 291)||4 Mpc (13.0 Mly )||0.001612||483|
|NGC 1023 Group (LGG 70)||6.12 Mpc (20.0 Mly )||0.002926||877|
|M101 Group (NGC 5457 Group, LGG 371)||7.33 Mpc (23.9 Mly )||0.001288||386|
|NGC 2997 Group (LGG 180)||7.66 Mpc (25.0 Mly )||0.002615||784|
|Canes Venatici II Group (Canes II Group)||8 Mpc (26.1 Mly )|
|M51 Group (NGC 5194 Group, LGG 347)||9.5 Mpc (31.0 Mly )||0.001850||555|
|Leo Triplet (M66 Group, NGC 3627 Group, LGG 231)||10.75 Mpc (35.1 Mly )||0.002207||662|
|Leo Group (Leo I Group, M96 Group, NGC 3379 Group, LGG 217)||11.66 Mpc (38.0 Mly )||0.002267||680|
|Draco Group||12.25 Mpc (40.0 Mly )|
|LGG 396 (NGC 5866 Group, NGC 5907 Group)||0.003020||905|
|Ursa Major Group (Ursa Major I Group, M109 Group, NGC 3992 Group, NGC 3726 Group, LGG 258)||16.88 Mpc (55.1 Mly )||0.003388||1016|
|Galaxy cluster||Distance||Redshift (z)||Recession velocity (km/s)||Notes|
|Virgo Cluster||18 Mpc (59 Mly )||0.0038||1139||The Virgo Cluster is at the core of the Virgo Supercluster. The Local Group is a member of the supercluster, but not the cluster.|
|Fornax Cluster (Abell S 373, AM 0336-353, MCL 52)||19 Mpc (62 Mly )||0.0046||1379|
|Antlia Cluster (Abell S 636)||40.7 Mpc (133 Mly )||0.0087||2608||Also called the Antlia Group.|
|Centaurus Cluster (Abell 3526, Cl 1247-4102)||52.4 Mpc||0.0110||3298|
|Hydra Cluster (Hydra I Cluster, Abell 1060, Cl 1034-2716)||58.3 Mpc||0.0114||3418|
|No entries yet|
|Galaxy cluster||Date||Redshift (z)||Recession Velocity |
|CL J1001+0220||2016 −||2.506|
| CL J1449+0856 |
|XMMXCS 2215-1738 (XMMXCS 2215.9-1738)||2006–2009||1.45||XMM-XCS 2215-1738 was also the most massive early cluster so far discovered.|
|RDCS 0848+4453 ( RDCS0848.6+4453, RX J0848+4453, ClG 0848+4453 )||1997–||1.276||ClG 0848+4453 forms a double-cluster supercluster with RDCS J0849+4452|
|galaxy cluster around 3C 324 (3C 234 Cluster)||1984–||1.206||At the time, the BCG, 3C324 was the most distant non-quasar galaxy.|
|Cl 1409+524||1960–1975||0.461||The measurement of 3C295's redshift in 1960 also defined its cluster's position. 3C 295 was also the most distant galaxy of the time.|
|Abell 732 (fainter Hydra Cluster Cl 0855+0321)||1951–1960||0.2||61 000||Attempts at measuring the redshift of the brightest cluster galaxy of this Hydra Cluster had been attempted for years before it had been successfully achieved. The BCG was also the most distant galaxy of the time.|
|Abell 1930 (Bootes Cluster)||1936–1951||0.13||39 000||The BCG of this cluster was also the most distant galaxy of the time.|
|Gemini Cluster (Abell 568)||1932 − 1936||0.075||23 000||The BCG of this cluster was the most distant galaxy at the time.|
|WH Christie's Leo Cluster||1931–1932||19 700||The BCG of this cluster was the most distant galaxy known at the time.|
|Baede's Ursa Major Cluster||1930–1931||11 700||The BCG of this cluster was the highest redshift galaxy of the time.|
|Coma Cluster||1929–1930||0.026||7 800||This cluster's distance was determined by one of the NGC objects lying in it, NGC4860.|
|Pegasus Group (LGG 473, NGC 7619 Group)||1929||0.012||3 779||The BCG for this group was used to measure its redshift. Shortly after this was publicized, it was accepted that redshifts were an acceptable measure of inferred distance.|
|Cetus Group (Holmberg 45, LGG 27)||1921–1929||0.006||1 800||NGC 584 (Dreyer 584) was measured for the redshift to this galaxy group.|
|Virgo Cluster||1784–1921||59 Mly (18 Mpc) |
|1 200||This was the first noted cluster of "nebulae" that would become galaxies. The first redshifts to galaxies in the cluster were measured in the 1910s. Galaxies were not identified as such until the 1920s. The distance to the Virgo Cluster would have to wait until the 1930s.|
|No entries yet|
|Galaxy protocluster||Date||Redshift (z)||Notes|
|COSMOS-AzTEC3||2011–||5.3||Located in Sextans, the cluster appears to contain 11 young small galaxies.|
|Protocluster around radio-galaxy TN J1338-1942||2002–||4.11||It was described as the most distant cluster.|
|Protocluster around 3C 368||1982–||1.13|
Sometimes clusters are put forward that are not genuine clusters or superclusters. Through the researching of member positions, distances, peculiar velocities, and binding mass, former clusters are sometimes found to be the product of a chance line-of-sight superposition.
|Cancer Cluster||The Cancer Cluster was found to be a random assortment of galaxy groups, and not a true cluster.|
|Coma-Virgo Cloud||The early identification of the Coma-Virgo Cloud of Nebulae was actually a mistaken identification due to the superposition of the Virgo Supercluster and Coma Supercluster, and not a Coma-Virgo Supercluster|
A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest known structures of the universe. The Milky Way is part of the Local Group galaxy group, which in turn is part of the Virgo Supercluster, which is part of the Laniakea Supercluster. The large size and low density of superclusters means that they, unlike clusters, expand with the Hubble expansion. The number of superclusters in the observable universe is estimated to be 10 million.
Serpens is a constellation of the northern hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations defined by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput to the west and Serpens Cauda to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in Serpens Caput and Nu Serpentis in Serpens Cauda.
Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. As a branch of astronomy, star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function. Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy approximately 2.5 million light-years from Earth and the nearest major galaxy to the Milky Way. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the Ethiopian princess who was the wife of Perseus in Greek mythology.
Lynx is a constellation named after the animal, usually observed in the Northern Celestial Hemisphere. The constellation was introduced in the late 17th century by Johannes Hevelius. It is a faint constellation, with its brightest stars forming a zigzag line. The orange giant Alpha Lyncis is the brightest star in the constellation, and the semiregular variable star Y Lyncis is a target for amateur astronomers. Six star systems have been found to contain planets. Those of 6 Lyncis and HD 75898 were discovered by the Doppler method; those of XO-2, XO-4, XO-5 and WASP-13 were observed as they passed in front of the host star.
Abell 2218 is a cluster of galaxies about 2 billion light-years away in the constellation Draco.
Messier 32 is a dwarf "early-type" galaxy about 2,650,000 light-years (810,000 pc) from our star system, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749. Its true size is about 3⁄4 of the radius of the Sun from the local galactic centre, 6,300–6,700 light-years (1,900–2,100 pc) at its quite unpronounced widest.
Redshift quantization, also referred to as redshift periodicity, redshift discretization, preferred redshifts and redshift-magnitude bands, is the hypothesis that the redshifts of cosmologically distant objects tend to cluster around multiples of some particular value. In standard inflationary cosmological models, the redshift of cosmological bodies is ascribed to the expansion of the universe, with greater redshift indicating greater cosmic distance from the Earth. This is referred to as cosmological redshift. Ruling out errors in measurement or analysis, quantized redshift of cosmological objects would either indicate that they are physically arranged in a quantized pattern around the Earth, or that there is an unknown mechanism for redshift unrelated to cosmic expansion, referred to as "intrinsic redshift" or "non-cosmological redshift".
In astronomy, a Lyman-alpha blob (LAB) is a huge concentration of a gas emitting the Lyman-alpha emission line. LABs are some of the largest known individual objects in the Universe. Some of these gaseous structures are more than 400,000 light years across. So far they have only been found in the high-redshift universe because of the ultraviolet nature of the Lyman-alpha emission line. Since the Earth's atmosphere is very effective at filtering out UV photons, the Lyman-alpha photons must be redshifted in order to be transmitted through the atmosphere.
NGC 4536 is an intermediate spiral galaxy in the constellation Virgo located about 10° south of the midpoint of the Virgo cluster. However, it is not considered a member of the cluster but is a member of the Virgo II Groups which form a southern extension of the Virgo Cluster. The morphological classification in the De Vaucouleurs system is SAB(rs)bc, which indicates it is a weakly barred spiral galaxy with a hint of an inner ring structure plus moderate to loosely wound arms. It does not have a classical bulge around the nucleus.
In cosmology, galaxy filaments are the largest known structures in the universe, consisting of walls of gravitationally bound galaxy superclusters. These massive, thread-like formations can reach 80 megaparsecs h−1 and form the boundaries between large voids.
NGC 4921 is a barred spiral galaxy in the Coma Cluster, located in the constellation Coma Berenices. It is about 320 million light-years from Earth. The galaxy has a nucleus with a bar structure that is surrounded by a distinct ring of dust that contains recently formed, hot blue stars. The outer part consists of unusually smooth, poorly distinguished spiral arms.
MACS J0647.7+7015 is a galaxy cluster with a redshift z = 0.592, located at J2000.0 right ascension 06h 47m 42s declination +70° 15′. It lies between the Big Dipper and Little Dipper in the constellation Camelopardalis. It is part of a sample of 12 extreme galaxy clusters at z > 0.5 discovered by the MAssive Cluster Survey (MACS).
NGC 4494 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 45 million light years from Earth, which, given its apparent dimensions, means that NGC 4494 is about 60,000 light years across. It was discovered by William Herschel in 1785.
NGC 3860 is a spiral galaxy located about 340 million light-years away in the constellation Leo. NGC 3860 was discovered by astronomer William Herschel on April 27, 1785. The galaxy is a member of the Leo Cluster and is a low-luminosity AGN (LLAGN). Gavazzi et al. however classified NGC 3860 as a strong AGN which may have been triggered by a supermassive black hole in the center of the galaxy.
NGC 4278 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4278 is about 65,000 light years across. It was discovered by William Herschel on March 13, 1785. NGC 4278 is part of the Herschel 400 Catalogue and can be found about one and 3/4 of a degree northwest of Gamma Comae Berenices even with a small telescope.