This article lists somegalaxy groups andgalaxy clusters.
Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to theMilky Way tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.
Some clusters exhibiting strong evidence ofdark matter.
| Galaxy cluster | Notes |
|---|---|
| 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.[2] |
| 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.[3] |
| 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.[4][5] |
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 of1E 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 isRCS2 J2327, agalaxy cluster with the mass of 2 quadrillion suns. | Also has a systematic designation ofACT-CL J0102-4915.[6][7][8] |
| Musket Ball Cluster | Named in comparison to theBullet Cluster, as this one is older and slower galaxy cluster merger than theBullet Cluster. | Also has a systematic designation ofDLSCL J0916.2+2951.[9] |
| 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 ofAbell 2744.[10] |
| Galaxy group | Origin of name | Notes |
|---|---|---|
| Local Group | The galaxy group that includes the Milky Way. | |
| Bullet Group | Named in comparison with theBullet Cluster, being of similar formation, except smaller. | Also has a systematic catalogue nameSL2S 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.[11][12] |
| Burbidge Chain | ||
| Copeland Septet | Discovered by British astronomerRalph Copeland in 1874. | |
| Deer Lick Group | Coined byTom 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 theNGC 7331 Group, after the brightest member of the group.[13] |
| 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 theVirgo Cluster. | |
| Robert's Quartet | It was named byHalton Arp andBarry F. Madore, who compiledA Catalogue of Southern Peculiar Galaxies and Associations in 1987. | Thiscompact 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 theNGC 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 — atidal stream caused by the merger. The group is, therefore, more properly calledHCG 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 calledHCG 92, because the name refers to a visual collection and not a group. Thus, the real group is also calledStephan's Quartet. |
| Wild's Triplet | Named after the British-born and Australia-based astronomerPaul Wild (1923–2008), who studied the trio in the early 1950s.[14] | |
| Zwicky's Triplet |
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.
TheLocal 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 twoMagellanic 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 theMilky Way'sspiral arms.
| Galaxy group | Visiblegalaxies | Notes |
|---|---|---|
| Local Group | 5 | Apart from theMilky Way, only 4 galaxies are visible to the naked eye.[15] |
| Centaurus A/M83 Group | 2 | TheCentaurus A galaxy has been spotted with the naked eye by Stephen James O'Meara[16][17] andM83 has also reportedly been seen with the naked eye.[18] |
| M81 Group | 1 | OnlyBode's Galaxy (M81, NGC 3031) is visible to the naked eye.[15][19] |
| First discovered | Name | Date | Notes |
|---|---|---|---|
| Galaxy cluster | Virgo Cluster | 1784 | Discovered by Charles Messier.[21] |
| Galaxy group | |||
| Compact group | The four brightest members ofStephan's Quintet | 1877 | Discovered by Edouard Stephan. |
| Proto-cluster | |||
| Double galaxy | Magellanic Clouds | antiquity |
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| Title | Name | Data | Notes | time |
|---|---|---|---|---|
| Most distant galaxy cluster | CL J1001+0220 | redshift z=2.506 | Announced August 2016. | [22] |
| Nearest galaxy cluster | Virgo Cluster | The Virgo Cluster is at the core of theVirgo Supercluster. TheLocal Group is a member of the supercluster, but not the cluster. | ||
| Most distant galaxy group | ||||
| Nearest galaxy group | Local Group | 0 distance | This is thegalaxy group that our galaxy belongs to. | |
| Nearest neighbouring galaxy group | IC 342/Maffei Group | |||
| Most distant proto-cluster | A2744z7p9OD | z=7.88 | [23] | |
| Nearest proto-cluster | ||||
| Most distant massive proto-cluster | z66OD | z=6.585 | At time of discovery in 2019, the object had 12 members, includingHimiko. | [24][25][26] |
| Least massive galaxy group | ||||
| Most massive galaxy cluster | RX J1347.5-1145 | mass= 2.0 ± 0.4 × 1015 MSun |
|
| 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 theVirgo Supercluster. TheLocal Group is a member of the supercluster, but not the cluster.[30] |
| Fornax Cluster (Abell S 373,AM 0336-353,MCL 52) | 19 Mpc (62 Mly) | 0.0046 | 1379 | [30] |
| Antlia Cluster (Abell S 636) | 40.7 Mpc (133 Mly) | 0.0087 | 2608 | Also called theAntlia Group. |
| Centaurus Cluster (Abell 3526,Cl 1247-4102) | 52.4 Mpc | 0.0110 | 3298 | [30] |
| Hydra Cluster (Hydra I Cluster,Abell 1060,Cl 1034-2716) | 58.3 Mpc | 0.0114 | 3418 | [30] |
| ||||
| Galaxy cluster | Distance | Notes | |
|---|---|---|---|
| No entries yet | |||
| |||
| Galaxy cluster | Date | Redshift (z) | Recession Velocity (km/s) | Notes |
|---|---|---|---|---|
| CL J1001+0220 | 2016 − | 2.506 | [22] | |
| CL J1449+0856 (ClG J1449+0856) | 2011–2016 | 2.07 | [31][32][33] | |
| JKCS 041 | 2009–2011 | 1.9 | ||
| 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.[34][35] | |
| ISCS J143809+341419 | 2005–2006 | 1.41 | [36][37] | |
| XMMU J2235.3-2557 | 2005 | 1.393 | [38][39][40][41] | |
| RDCS 0848+4453 (RDCS0848.6+4453,RX J0848+4453,ClG 0848+4453 ) | 1997– | 1.276 | ClG 0848+4453 forms a double-cluster supercluster withRDCS J0849+4452[42][43][44][45][46] | |
| galaxy cluster around3C 324 (3C 234 Cluster) | 1984– | 1.206 | At the time, the BCG,3C324 was the most distant non-quasar galaxy.[47] | |
| Cl 1409+524 | 1960–1975 | 0.461 | The measurement of3C295's redshift in 1960 also defined its cluster's position. 3C 295 was also the most distant galaxy of the time.[48][49] | |
| Abell 732 (fainter Hydra ClusterCl 0855+0321) | 1951–1960 | 0.2 | 61 000 | Attempts at measuring the redshift of thebrightest 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.[48][50][51][52] |
| Abell 1930 (Bootes Cluster) | 1936–1951 | 0.13 | 39 000 | The BCG of this cluster was also the most distant galaxy of the time.[51][53] |
| Gemini Cluster (Abell 568) | 1932 − 1936 | 0.075 | 23 000 | The BCG of this cluster was the most distant galaxy at the time.[53][54] |
| WH Christie's Leo Cluster | 1931–1932 | 19 700 | The BCG of this cluster was the most distant galaxy known at the time.[51][54][55][56][57] | |
| Baede's Ursa Major Cluster | 1930–1931 | 11 700 | The BCG of this cluster was the highest redshift galaxy of the time.[57][58] | |
| Coma Cluster | 1929–1930 | 0.026 | 7 800 | This cluster's distance was determined by one of the NGC objects lying in it,NGC4860.[58][59] |
| 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.[60] |
| 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.[60][61][62][63] |
| Virgo Cluster | 1784–1921 | 59 Mly (18 Mpc) z=0.003 | 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.[21] |
| ||||
| Galaxy protocluster | Distance | Notes | |
|---|---|---|---|
| No entries yet | |||
| |||
| Galaxy protocluster | Date | Redshift (z) | Notes |
|---|---|---|---|
| BoRG-58 | 2012 | ~ 8 | [72] |
| COSMOS-AzTEC3 | 2011– | 5.3 | Located inSextans, the cluster appears to contain 11 young small galaxies.[73][74] |
| Protocluster around radio-galaxyTN J1338-1942 | 2002– | 4.11 | It was described as the most distant cluster.[75][76][77][78] |
| Protocluster around3C 368 | 1982– | 1.13 | [79] |
| |||
Sometimes clusters are put forward that are not genuine clusters or superclusters. Through the researching of member positions,distances,peculiar velocities, andbinding mass, former clusters are sometimes found to be the product of a chance line-of-sight superposition.
| Formercluster | Notes |
|---|---|
| Cancer Cluster | The Cancer Cluster was found to be a random assortment of galaxy groups, and not a true cluster.[21] |
| Coma-Virgo Cloud | The early identification of theComa-Virgo Cloud of Nebulae was actually a mistaken identification due to the superposition of theVirgo Supercluster andComa Supercluster, and not aComa-Virgo Supercluster |
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