List of galaxy clusters - AbsoluteAstronomy.com

This page lists some of the more interesting galaxy cluster

Galaxy cluster

A galaxy cluster is a compact cluster of galaxies. Basic difference between a galaxy group and a galaxy cluster is that there are many more galaxies in a cluster than in a group. Also, galaxies in a cluster are more compact and have higher velocity dispersion. One of the key features of cluster is...

s and groups.

Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way

Milky Way

The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.

List of groups and clusters

Galaxy cluster	Notes
Bullet Cluster Bullet cluster The Bullet cluster consists of two colliding clusters of galaxies. Studies of the Bullet cluster, announced in August 2006, provide the best evidence to date for the existence of dark matter...	This collision between two galaxy clusters seems to have left a dark matter cluster in the space between them.
Abell 520 Abell 520 The Abell 520 galaxy cluster is an unusual structure resulting from a major merger. It has been popularly nicknamed The Train Wreck Cluster, due to its chaotic structure....	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 Abell 2142 Abell 2142, or A2142, is a huge, X-ray luminous galaxy cluster in the constellation Corona Borealis. It is the result of a still ongoing merger between two galaxy clusters. The combined cluster is six million light years across, contains hundreds of galaxies and enough gas to make a thousand more...	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.

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 Local Group The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...		This is the galaxy group that we belong to.
Bullet Cluster Bullet cluster The Bullet cluster consists of two colliding clusters of galaxies. Studies of the Bullet cluster, announced in August 2006, provide the best evidence to date for the existence of dark matter...		This is actually two galaxy clusters in collision.
Burbidge Chain
Copeland Septet
Deer Lick Group Deer Lick Group NGC 7331 Group group of galaxies in constellation Pegasus. NGC 7331 spiral galaxy is the brightest member of the group. This group is also called the Deer Lick Group -External links:* * *...	Coined by Tomm 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.	It is also called the NGC 7331 Group, after the brightest member of the group.
Leo Triplet Leo Triplet The Leo Triplet is a small group of galaxies about 35 million light-years away in the constellation Leo. This galaxy group consists of the spiral galaxies M65, the M66, and the NGC 3628.-Members:...	This is named for the fact it contains only three galaxies.	This small group of galaxies lies in the constellation Leo.
Markarian's Chain Markarian's Chain Markarian's Chain is a stretch of galaxies that forms part of the Virgo Cluster. It's called a "chain" because, when viewed from Earth, the galaxies lie along a smoothly curved line. It was named after the Armenian astrophysicist, B. E. Markarian, who discovered their common motion in the early...		This stretch of galaxies forms part of the Virgo Supercluster Virgo Supercluster The Virgo Supercluster or Local Supercluster is the irregular supercluster that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs... .
Robert's Quartet Robert's Quartet Robert's Quartet is a compact galaxy group approximately 160 million light-years away in the constellation Phoenix. It is a family of four very different galaxies in the process of colliding and merging. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the...	It was named by Halton Arp Halton Arp Halton Christian Arp is an American astronomer. He is known for his 1966 Atlas of Peculiar Galaxies, which catalogues many examples of interacting and merging galaxies... and Barry F. Madore, who compiled A Catalogue of Southern Peculiar Galaxies and Associations in 1987.	This is compact group of galaxies lies 160 million light-years away in the Phoenix constellation.
Seyfert's Sextet Seyfert's Sextet Seyfert's Sextet is a group of galaxies about 190 million light-years away in the constellation Serpens Caput. The group appears to contain six members, but one of the galaxies is a background object and another "galaxy" is actually a separated part of one of the other galaxies. The gravitational...	This is named after its discoverer, Carl Seyfert, and at the time it appeared to contain six external nebulae. It is also called the NGC 6027 Sextet, after its brightest element.	There are actually only five galaxies in the sextet, and only four galaxies in the compact group, one of the "galaxies" is actually part of another of the galaxies. The group is therefore more properly called HCG 79, because the name refers to a visual collection and not a cluster. HCG 79 lies 190 million light-years away in the Serpens Caput constellation.
Stephan's Quintet Stephan's Quintet Stephan's Quintet in the constellation Pegasus is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group was discovered by Édouard Stephan in 1877 at Marseilles Observatory.... (Stephan's Quartet)	This is 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 cluster. Thus, the real group is also called Stephan's Quartet
Wild's Triplet
Zwicky's Triplet

Major nearby groups and clusters are generally named after the constellation they lie in. Many groups and clusters are named after the leading galaxy in the group or cluster. This represents an ad hoc systematic naming system.

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

Local Group

The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...

, 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

Magellanic Clouds

The two Magellanic Clouds are irregular dwarf galaxies visible in the southern hemisphere, which are members of our Local Group and are orbiting our Milky Way galaxy...

, as a pair of galaxies, is visually discernible. The Maffei Group, the nearest galaxy group, would be visible by the naked eye if it were not obscured by the stars and dust clouds of the galactic nucleus.

Galaxy cluster	Number of visible galaxies	Notes
Local Group Local Group The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...	5	If we exclude the Milky Way Galaxy, only 4 galaxies are visible to the naked-eye.
M81 Group M81 Group The M81 Group is a group of galaxies in the constellation Ursa Major that includes the well-known galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the...	1	Only Bode's Galaxy (M81, NGC 3031) is visible to the naked-eye.
Centaurus A/M83 Group	2	Both Centaurus A Centaurus A Centaurus A 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 and distance... and M83 have been seen with the naked eye
Sculptor Group Sculptor Group The Sculptor Group is a loose group of galaxies near the south galactic pole. The group is one of the closest groups of galaxies to the Local Group; the distance to the center of the group from the Milky Way is approximately 3.9 Mpc.... (South Polar Group)	1	Only the Sculptor Galaxy Sculptor Galaxy The Sculptor Galaxy is an intermediate spiral galaxy in the constellation Sculptor... (NGC 253) can be seen with the naked eye.

Firsts

First	Galaxy cluster	Date	Notes
First galaxy cluster discovered	Virgo Cluster Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...	1784	It was discovered by Charles Messier
First galaxy group discovered
First compact galaxy group discovered	Stephan's Quartet (Stephan's Quintet Stephan's Quintet Stephan's Quintet in the constellation Pegasus is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group was discovered by Édouard Stephan in 1877 at Marseilles Observatory.... )	1877	It was discovered by Edouard Stephan.
First proto-cluster discovered
First double galaxy discovered	Magellanic Clouds Magellanic Clouds The two Magellanic Clouds are irregular dwarf galaxies visible in the southern hemisphere, which are members of our Local Group and are orbiting our Milky Way galaxy...	antiquity

Extremes

Title	Galaxy cluster	Data	Notes
Most distant galaxy cluster	ClG J1449+0856	z Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... =2.07
Nearest galaxy cluster	Virgo Cluster Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...		This cluster is the core cluster of the galaxy supercluster our galaxy group belongs to.
Most distant galaxy group
Nearest galaxy group	Local Group Local Group The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...	0 distance	This is the galaxy group that our galaxy belongs to.
Nearest neighbouring galaxy group
Most distant massive proto-cluster	COSMOS-AzTEC3	z=5.3 12.6 billion light years
Least massive galaxy group
Most massive galaxy cluster	RX J1347.5-1145	mass= 2.0 ± 0.4 × 10¹⁵ M_Sun distance: z= 0.451 L_X-ray = 6.0 ± 0.1 × 10⁴⁵ erg/s in the [2-10] keV energy band temperature: kT = 10.0 ± 0.3 keV
Most massive distant galaxy cluster	2XMM J083026+524133	mass= 5.6 × 10¹⁴ M_Sun distance: z= 0.99 ± 0.03 L_bolometric= 1.8 × 10⁴⁵ erg/s temperature= 8.2 ± 0.9 keV ( ~95 MK for the intra-cluster gas )	The hottest, most X-ray luminous cluster at redshifts z ≥ 1 (z= 0.99 ± 0.03).

Closest groups and clusters

Galaxy Groups closer than the Virgo Cluster
Galaxy cluster	Distance	Spectral shift	Notes
Local Group Local Group The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...	0	0	This is the galaxy group that our galaxy belongs to.
LGG 104 (IC 342/Maffei Group , IC 342 / Maffei 1 Group , IC 342 Maffei 1-2 Group)		z=0.000868	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 1 Group The IC 342/Maffei Group is the nearest group of galaxies to the Local Group. The group can be described as a binary group; the member galaxies are mostly concentrated around either IC 342 or Maffei 1, both of which are the brightest galaxies within the group... , Maffei Group).
M81 Group M81 Group The M81 Group is a group of galaxies in the constellation Ursa Major that includes the well-known galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the... (NGC 3031 Group)	11 Mly (3.5Mpsc)	z=0.001115
Centaurus A/M83 Group (Centarus A Group , M83 Group M83 Group The Centaurus A/M83 Group is a complex group of galaxies in the constellations Hydra, Centaurus, and Virgo. The group may be roughly divided into two subgroups. The Cen A Subgroup, at a distance of 11.9 Mly , is centered around Centaurus A, a nearby radio galaxy... )	12 Mly (3.66Mpsc)	z=0.000999	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 M83 Group The Centaurus A/M83 Group is a complex group of galaxies in the constellations Hydra, Centaurus, and Virgo. The group may be roughly divided into two subgroups. The Cen A Subgroup, at a distance of 11.9 Mly , is centered around Centaurus A, a nearby radio galaxy... , NGC 5236 Group , LGG 355).
Sculptor Group Sculptor Group The Sculptor Group is a loose group of galaxies near the south galactic pole. The group is one of the closest groups of galaxies to the Local Group; the distance to the center of the group from the Milky Way is approximately 3.9 Mpc.... (South Polar Group)	12.75 Mly (3.9Mpsc)
Canes Venatici Group (Canes Venatici I Group , Canes I Group , M94 Group M94 Group The M94 Group is a loose, extended group of galaxies located about 13 million light-years away in the constellations Canes Venatici and Coma Berenices. The group is one of many groups that lies within the Virgo Supercluster The M94 Group (Canes Venatici I Group) is a loose, extended group of... , NGC 4736 Group , LGG 291)	13 Mly (4Mpsc)	z=0.001612
NGC 1023 Group NGC 1023 Group The NGC 1023 group is a group of galaxies about 20.6 million light-years away from Earth. The group resides in the Canes Venatici Cloud in the Virgo Supercluster.-Members:* Probable : DDO 024, DDO 025.... (LGG 70)	20 Mly (6.12Mpsc)	z=0.002926
M101 Group M101 Group The M101 Group is a loose group of galaxies located in Ursa Major. The group is named after the brightest galaxy in the group, the Pinwheel Galaxy . Most of the other members of the group are companions of the Pinwheel Galaxy. The group itself is one of many located within the Virgo Supercluster... (NGC 5457 Group , LGG 371)	24 Mly (7.33Mpsc)	z=0.001288
NGC 2997 Group NGC 2997 Group The NGC 2997 group is a group of galaxies about 24.8 million light-years from Earth containing NGC 2997 as a member. It is a group in the Local Supercluster along with the Local Group.- References :... (LGG 180)	25 Mly (7.66Mpsc)	z=0.002615
Canes Venatici II Group (Canes II Group Canes II Group The Canes II Group or Canes Venatici II Group is a group of galaxies about 26.1 million light-years away from Earth. The group resides in the Local Supercluster... )	26 Mly (8Mpsc)
M51 Group M51 Group The M51 Group is a group of galaxies located in Canes Venatici. The group is named after the brightest galaxy in the group, the Whirlpool Galaxy... (NGC 5194 Group , LGG 347)	31 Mly (9.5Mpsc)	z=0.001850
Leo Triplet Leo Triplet The Leo Triplet is a small group of galaxies about 35 million light-years away in the constellation Leo. This galaxy group consists of the spiral galaxies M65, the M66, and the NGC 3628.-Members:... (M66 Group , NGC 3627 Group , LGG 231)	35 Mly (10.75Mpsc)	z=0.002207
Leo Group (Leo I Group , M96 Group M96 Group The M96 Group is a group of galaxies in the constellation Leo. This group contains between 8 and 24 galaxies, including three Messier objects. The group is one of many groups that lies within the Virgo Supercluster The M96 Group (also known as the Leo I Group) is a group of galaxies in the... , NGC 3379 Group , LGG 217)	38 Mly (11.66Mpsc)	z=0.002267
Draco Group	40 Mly (12.25Mpsc)
LGG 396 (NGC 5866 Group NGC 5866 Group The NGC 5866 Group is a small group of galaxies located in the constellation Draco. The group is named after NGC 5866, the galaxy with the highest apparent magnitude in the group, although some galaxy group catalogs list NGC 5907 as the brightest member.... , NGC 5907 Group)		z=0.003020
Ursa Major Group (Ursa Major I Group , M109 Group , NGC 3992 Group , NGC 3726 Group , LGG 258)	55 Mly (16.88Mpsc)	z=0.003388
Mly represents millions of light-year Light-year A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres... s, a measure of distance. Distances are measured from Earth, with Earth being at zero.

10 Closest Clusters
Galaxy cluster	Distance	Notes
Virgo Cluster Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member... (Virgo I Cluster)	z=0.0038 59 Mly (18Mpsc)	This is the core cluster of the supercluster our galaxy group belongs to.
Fornax Cluster Fornax Cluster At a distance of approximately 62.0 Mly , the Fornax Cluster is the second richest cluster of galaxies within 100 million light-years, although it is much smaller than the Virgo Cluster. It lies primarily in the constellation Fornax, and may be associated with the nearby Eridanus Group... (Abell S 373 , AM 0336-353 , MCL 52)	z=0.0046
Antlia Cluster Antlia Cluster The Antlia Cluster is a cluster of galaxies located in the Hydra-Centaurus Supercluster. The Antlia Cluster is the third nearest to our Local Group after the Virgo Cluster and Fornax Cluster. The cluster's distance from earth is 32.58 - 32.71 Mly away and can be viewed from earth in the... (Abell S 636)	z=0.0087 32.66 Mly (10Mpsc)	Also called the Antlia Group.
Centaurus Cluster Centaurus Cluster The Centaurus Cluster is a cluster of hundreds of galaxies, located approximately 155 million light years away in the Centaurus constellation. The brightest member galaxy is the elliptical galaxy NGC 4696... (Abell 3526 , Cl 1247-4102)	z=0.0110
Hydra Cluster Hydra Cluster The Hydra Cluster is a cluster of galaxies that contains 157 bright galaxies and can be viewed from earth in the constellation Hydra. The cluster spans about ten million light years and has an unusual high proportion of dark matter. The cluster is part of the Hydra-Centaurus Supercluster located... (Hydra I Cluster , Abell 1060 , Cl 1034-2716)	z=0.0114
Mly represents millions of light-year Light-year A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres... s, a measure of distance. z represents redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... , a measure of recessional velocity and inferred distance due to cosmological expansion Distances are measured from Earth, with Earth being at zero.

Closest Neighbouring Cluster or Group Recordholder
Galaxy cluster	Date	Distance	Notes
Local Group Local Group The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...	always (closest group or cluster) 1936 − eternity	0 for reference	Components of the Local Group have always been visible in the night sky. However, the Local Group as a group was identified in 1936. This is the closest cluster to us, as our galaxy is a member of it.
M81 Group M81 Group The M81 Group is a group of galaxies in the constellation Ursa Major that includes the well-known galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the... (NGC 3031 Group)		11 Mly (3.5Mpsc)
M83 Group M83 Group The Centaurus A/M83 Group is a complex group of galaxies in the constellations Hydra, Centaurus, and Virgo. The group may be roughly divided into two subgroups. The Cen A Subgroup, at a distance of 11.9 Mly , is centered around Centaurus A, a nearby radio galaxy... (NGC 5236 Group , LGG 355)			The BCG of this subgroup had its redshift determined early on.
Virgo Cluster Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...	1784 - (group or cluster) 1784 - eternity (cluster)	59 Mly (18Mpsc)	This was the first noted cluster of "nebulae" that would become galaxies. Galaxies were not identified as such until the 1920s. This is still the nearest cluster of galaxies to us.
Mly represents millions of light-year Light-year A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres... s, 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 Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... , a measure of recessional velocity and inferred distance due to cosmological expansion

Remotest Cluster Titleholder
Galaxy cluster	Date	Distance	Notes
CL J1449+0856 (ClG J1449+0856)	2011-	z=2.07
JKCS 041 JKCS 041 JKCS 041 is a group of galaxies with the distinction of being the farthest away group from Earth ever observed, as of 2009. It is estimated to be 10.2 billion light years away, seen at redshift 1.9. The cluster is located in the constellation Cetus at a photometrically determined redshift of z=1.9...	2009–2011	z=1.9
XMMXCS 2215-1738 XMMXCS 2215-1738 XMMXCS 2215-1738 is a galaxy cluster that lies 10 billion light-years away, or redshift z=1.45 . It was discovered by the XMM Cluster Survey in 2006.... (XMMXCS 2215.9-1738)	2006–2009	z=1.45	XMM-XCS 2215-1738 was also the most massive early cluster so far discovered.
ISCS J143809+341419	2005–2006	z=1.41
XMMU J2235.3-2557	2005	z=1.393
RDCS 0848+4453 ( RDCS0848.6+4453 , RX J0848+4453 , ClG 0848+4453 )	1997 -	z=1.276	ClG 0848+4453 forms a double-cluster supercluster with RDCS J0849+4452
galaxy cluster around 3C 324 (3C 234 Cluster)	1984 -	z=1.206	At the time, the BCG, 3C324 was the most distant non-quasar galaxy.
Cl 1409+524	1960 − 1975	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 − 1960	z=0.2 (V=61000 km/s)	Attempts at measuring the redshift of the brightest cluster galaxy Brightest cluster galaxy Brightest cluster galaxy is defined as the brightest galaxy in a cluster of galaxies. BCGs include the most massive galaxies in the universe. They are generally elliptical galaxies which lie close to the geometric and kinematical center of their host galaxy cluster, hence at the bottom of the... 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	z=0.13 (V=39000 km/s)	The BCG of this cluster was also the most distant galaxy of the time.
Gemini Cluster (Abell 568)	1932 − 1936	z=0.075 (V=23000 km/s)	The BCG of this cluster was the most distant galaxy at the time.
WH Christie's Leo Cluster	1931 − 1932	z= (V=19700 km/s)	The BCG of this cluster was the most distant galaxy known at the time.
Baede's Ursa Major Cluster	1930 − 1931	z= (V=11700 km/s)	The BCG of this cluster was the highest redshift galaxy of the time.
Coma Cluster	1929 − 1930	z=0.026 (V=7800 km/s)	This cluster's distance was determined by one of the NGC objects lying in it, NGC4860.
Pegasus Group (LGG 473 , NGC 7619 Group)	1929	z=0.012 (V=3779 km/s)	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	z=0.006 (V=1800 km/s)	NGC 584 NGC 584 NGC 584 is an elliptical galaxy in the constellation Cetus. The galaxy was discovered on 10 September 1785 by the German-British astronomer William Herschel.-External links:*... (Dreyer 584) was measured for the redshift to this galaxy group.
Virgo Cluster Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...	1784 − 1921	59 Mly (18Mpsc) z=0.003 (V=1200 km/s)	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.
z represents redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... , a measure of recessional velocity and inferred distance due to cosmological expansion

In 2003 RDCS 1252-29 (RDCS1252.9–2927) at z=1.237, was found to be the most distant rich cluster, which lasted until 2005.

In 2000, a cluster was announced in the field of quasar QSO 1213-0017 at z=1.31 (the quasar lies at z=2.69)

In 1999, cluster RDCS J0849+4452 (RX J0849+4452, RXJ0848.9+4452) was found at z=1.261

In 1995 and 2001, the cluster around 3C 294 was announced, at z=1.786

In 1992, observations of the field of cluster Cl 0939+4713 found what appears to be a background cluster near a quasar, also in the background. The quasar was measured at z=2.055 and it was assumed that the cluster would be as well.

In 1975, 3C 123 and its galaxy cluster was incorrectly determined to lie at z=0.637 (actually z=0.218)

In 1958, cluster Cl 0024+1654 and Cl 1447+2619 were estimated to have redshifts of z=0.29 and z=0.35 respectively. However, they were not spectroscopically determined.

5 Farthest Protoclusters
Galaxy cluster	Distance	Notes
z represents redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... , a measure of recessional velocity and inferred distance due to cosmological expansion

Most Remote Proto-Cluster Titleholder
Galaxy protocluster	Date	Distance	Notes
COSMOS-AzTEC3	2011 -	z=5.3	Located in Sextans Sextans Sextans is a minor equatorial constellation which was introduced in 1687 by Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his observations.-Notable features:... , the cluster appears to contain 11 young small galaxies.
proto-cluster around radio-galaxy TN J1338-1942	2002 -	z=4.11	It was described as the most distant cluster.
proto-cluster around 3C 368	1982 -	z=1.13
z represents redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... , a measure of recessional velocity and inferred distance due to cosmological expansion

In 2002, a very large, very rich proto-cluster, or the most distant proto-supercluster was found in the field of galaxy cluster MS 1512+36, around the gravitationally lensed galaxy MS 1512-cB58, at z=2.724

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 Cancer cluster Cancer cluster is a term used by epidemiologists, statisticians, and public health workers to define an occurrence of a greater-than-expected number of cancer cases within a group of people in a geographic area over a period of time....	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 Virgo Supercluster The Virgo Supercluster or Local Supercluster is the irregular supercluster that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs... and Coma Supercluster Coma Supercluster The Coma Supercluster is a nearby supercluster of galaxies comprising the Coma Cluster and the Leo Cluster . Located 300 million light-years from Earth, it is in the center of the Great Wall. The Coma Supercluster is the nearest massive cluster of galaxies to our own Virgo Supercluster... , and not a Coma-Virgo Supercluster

Lists of groups and clusters

Local Supercluster
ACO
Abell catalogue
The Abell catalog of rich clusters of galaxies is an all-sky catalog of 4,073 rich galaxy clusters of nominal redshift z 18.0*Galactic-Latitude: Areas of the sky in the neighbourhood of the Milky Way were excluded from the study because the density of stars in those fields—not to mention...

:List of Abell clusters
HCG
Hickson Compact Group
A Hickson Compact Group is a collection of galaxies designated as published by Paul Hickson in 1982.The most famous group on Hickson’s list of 100 objects is HCG 92, Stephan's Quintet....

:List of HCGs

External links

Astrophysical Journal Supplement, vol. 3, p. 211 (1958) The Distribution of Rich Clusters of Galaxies ; Abell's 1957 cluster list