List of galaxy groups and clusters


This page 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.

Clusters exhibiting strong evidence of dark matter

Some clusters exhibiting strong evidence of dark matter.
Galaxy clusterNotes
Bullet ClusterIn 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, collision-less matter is inferred to be present to account for the extra lensing around otherwise low-mass regions.
Abell 520This 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 2142A collision between two massive, X-ray luminous galaxy clusters.
Cl 0024+17
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.

Named groups and clusters

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.

Clusters

Galaxy clusterOrigin of nameNotes
Bullet ClusterThe cluster is named for the merger of two clusters colliding like a bulletAlso has a systematic designation of 1E 0657-56
El GordoNamed for its size, El Gordo is the biggest cluster found in the distant universe, at the time of discovery in 2011, with a mass of 3 quadrillion suns. 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 ClusterNamed 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 ClusterNamed 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.

Groups

Galaxy groupOrigin of nameNotes
Local GroupThe galaxy group that includes the milky way
Bullet GroupNamed 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.
Burbidge Chain
Copeland SeptetDiscovered by British astronomer Ralph Copeland in 1874.
Deer Lick GroupCoined by Tom Lorenzin 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 TripletNamed for the fact it contains only three galaxies.This small group of galaxies lies in the constellation Leo.
Markarian's ChainThis stretch of galaxies forms part of the Virgo Cluster.
Robert's QuartetIt 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 SextetNamed 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 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 TripletNamed after the British-born and Australia-based astronomer Paul Wild, who studied the trio in the early 1950s.
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.

Groups and clusters visible to the unaided eye

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 groupVisible galaxiesNotes
Local Group5Apart from the Milky Way, only 4 galaxies are visible to the naked eye.
Centaurus A/M83 Group2The 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 Group1Only Bode's Galaxy is visible to the naked eye.

First discoveredNameDateNotes
Galaxy clusterVirgo Cluster1784Discovered by Charles Messier.
Galaxy group
Compact groupThe four brightest members of Stephan's Quintet1877Discovered by Edouard Stephan.
Proto-cluster
Double galaxyMagellanic Cloudsantiquity

Extremes

TitleNameDataNotes
Most distant galaxy clusterCL J1001+0220redshift z=2.506Announced August 2016.
Nearest galaxy clusterVirgo ClusterThe 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 groupLocal Group0 distanceThis is the galaxy group that our galaxy belongs to.
Nearest neighbouring galaxy groupIC 342/Maffei Group
Most distant proto-clusterBoRG-58z~=8
Nearest proto-cluster
Most distant massive proto-clusterz66ODz=6.585At time of discovery in 2019, the object had 12 members, including Himiko.
Least massive galaxy group
Most massive galaxy clusterRX J1347.5-1145mass= 2.0 ± 0.4 × 1015 MSun
  • distance: z= 0.451
  • LX-ray = 6.0 ± 0.1 × 1045 erg/s in the keV energy band
  • temperature: kT = 10.0 ± 0.3 keV

Closest groups

Closest clusters

Farthest clusters

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.
Former clusterNotes
Cancer ClusterThe Cancer Cluster was found to be a random assortment of galaxy groups, and not a true cluster.
Coma-Virgo CloudThe 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

Lists of groups and clusters