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List of galaxy groups and clusters

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This page lists some of the more interesting galaxy clusters and groups.

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.

Nearby groups and clusters

List of named clusters

This is a list of galaxy clusters and groups 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
Local Group This is the galaxy group that we belong to.
Bullet Cluster This is actually two galaxy clusters in collision.
Leo Triplet This is named for the fact it contains only three galaxies. This small group of galaxies lies in the constellation Leo.
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 is a compact group of galaxies.
Seyfert's Sextet This is named after its discoverer, Carl Seyfert, and at the time it appeared to contain six external nebulae. There are actually only five galaxies in the sextet, and only four galaxies in the compact group. The group is therefore more properly called HCG 79, because the name refers to a visual collection and not a cluster.
Stephan's Quintet This is named after its discoverer, Édouard Stephan. There are actually only four galaxies in the compact group, the other galaxy is a background galaxy. The group is therefore more properly called HCG 92, because the name refers to a visual collection and not a cluster.

List of naked-eye groups

There is only one galaxy group or cluster visible to the naked eye, that would be our group of galaxies, the Local Group, if the requirement of visually sighting a cluster requires two or more galaxies. If the requirement also requires that the galaxies been somewhat close together in the sky, then no group or cluster is visually identifiable. However, the Magellanic Clouds, as a pair of galaxies, is visually discernable.

Galaxy cluster Number of visible galaxies Notes
Local Group 5 If we exclude the Milky Way Galaxy, only 4 galaxies are visible to the naked-eye. [1]
M81 Group 1 Only Bode's Galaxy (M81, NGC 3031) is visible to the naked-eye. [1] [2]

Closest groups and clusters

5 Closest Clusters
Galaxy cluster Distance Notes
Local Group 0 This is the galaxy group that our galaxy belongs to.

  • Mly represents millions of light-years, a measure of distance.
  • Distances are measured from Earth, with Earth being at zero.

Closest Cluster Recordholder
Galaxy cluster Date Distance Notes
Local Group always


1936 − eternity

0 Components of the Local Group have always been visible in the night sky. However, the Local Group as a group was identified in 1936. [3]
Virgo Cluster 1784 - 59 Mly (18Mpsc) This was the first noted cluster of "nebulae" that would become galaxies. Galaxies were not identified as such until the 1920's. [3]

  • Mly represents millions of light-years, a measure of distance.
  • Distances are measured from Earth, with Earth being at zero.

Farthest clusters

5 Furthest Clusters
Galaxy cluster Distance Notes

  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion
Remotest Cluster Titleholder
Galaxy cluster Date Distance Notes
XMMXCS 2215-1738 2006 - z=1.45
XMMU J2235.3-2557 2005 - z=1.393 [4] [5] [6]
RDCS 1252-29 z=1.24 [6] [4]
Cl 1409+524 1960 - z=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 - z=0.2 (V=61000km/s) Attempts at measuring the redshift of the brightest cluster galaxy of this Hydra Cluster had been attempted for years before it had been sucessfully acheived. The BCG was also the most distant galaxy of the time.
Abell 1930 (Bootes Cluster) 1936 - z=0.13 (V=39000km/s) The BCG of this cluster was also the most distant galaxy of the time.
Virgo Cluster 1784 - 59 Mly (18Mpsc)
z= (V=1200km/s) 		This was the first noted cluster of "nebulae" that would become galaxies. Galaxies were not identified as such until the 1920's. The distance to the Virgo Cluster would have to wait until the 1930's. [3]

  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion

False clusters

Through researching of galaxy association, sometimes clusters are put forward that are not genuine clusters or superclusters, but rather random collections of groups that chance alignment makes it seem is a cluster.

Galaxy cluster Notes
Cancer Cluster The Cancer Cluster was found to be a random assortment of galaxy groups, and not a true cluster. [3]
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

Lists of groups and clusters

Citations

  1. ^ a b http://www.uitti.net/stephen/astro/essays/farthest_naked_eye_object.shtml
  2. ^ SEDS, Messier 81
  3. ^ a b c d Template:PDF arXiv, FROM MESSIER TO ABELL: 200 YEARS OF SCIENCE WITH GALAXY CLUSTERS
  4. ^ a b New Scientist, Most distant galaxy cluster yet is revealed, 08:00 02 March 2005
  5. ^ [http://www.astro.lsa.umich.edu/~cmullis/research/xmmuj2235/index.html The Most Distant X-ray Massive Galaxy Cluster XMMU J2235.3-2557 z=1.4]
  6. ^ a b Template:PDF MAX-PLANCK-INSTITUT FÜR EXTRATERRESTRISCHE PHYSIK, GARCHING, GERMANY ; DEPARTMENT OF ASTRONOMY, UNIVERSITY OF MICHIGAN, ANN ARBOR, USA ; ESO, ASTROPHYSIKALISCHES INSTITUT, POTSDAM, GERMANY ; GALAXY CLUSTER ARCHAEOLOGY ; HANS BÖHRINGER, CHRISTOPHER MULIS, PIERO ROSATI, GEORG LAMER, RENE FASSBENDER, AXEL SCHWOPE, PETER SCHUECKER

See also

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