The Coma Supercluster

The Coma supercluster is a very famous supercluster. This map below is a plot of the brightest galaxies (from the Principal Galaxies Catalogue) in this region of the sky. Dominating this picture is the Virgo cluster - the nearest rich cluster in the universe and the dominant cluster in the the Virgo supercluster. Above the Virgo cluster and much further away are two much richer clusters - A1367 and A1656. These are the two main clusters in the Coma supercluster.

The Coma Supercluster

Below is a list of the major clusters in the Coma Supercluster. The supercluster contains only two major clusters of galaxies. They are both very rich clusters with a richness class of 2, although A1656 is larger and richer than A1367.

   1             2       3        4         5       6      7         
 Abell           Equatorial    Redshift  Distance  Rich  Notes       
 Number         Coordinates       z        Mly                       
                RA       Dec                                         
 A1367        11 44.5  +19 50   .0208      290      2    Leo cluster 
 A1656        12 59.8  +27 59   .0219      305      2    Coma cluster

Below is a list of some of the other major groups in the vicinity of the Coma supercluster. Some of these groups are foreground groups that lie between the Virgo and Coma superclusters. These two superclusters are connected to each other through some minor walls of galaxies.

   1             2       3        4         5       6      7         
 Group           Equatorial    Redshift  Distance  Rich  Notes       
 Name           Coordinates       z        Mly                       
                RA       Dec                                         
IC 698        11 28.7  +09 04   .0210      290                       
UGC6583       11 36.9  +19 58   .0214      295           A1367-West  
NGC3801       11 40.9  +17 27   .0108      150                       
NGC3902       11 50.5  +25 59   .0120      165                       
NGC3995       11 57.0  +32 19   .0106      145                       
NGC4005       11 58.2  +25 11   .0153      210                       
NGC4017       11 58.4  +27 46   .0114      160                       
NGC4065       12 04.5  +20 18   .0235      325                       
NGC4169       12 12.1  +29 07   .0127      175                       
NGC4213       12 15.8  +23 58   .0233      320                       
NGC4956       13 06.4  +35 14   .0160      220                       
NGC5056       13 21.7  +31 35   .0214      295           A1656-East  
NGC5127       13 24.6  +31 30   .0162      225                       
NGC5174       13 29.5  +11 44   .0232      320                       
IC 944        13 52.0  +14 05   .0234      325                       
IC4342        13 55.4  +25 05   .0293      405                       
Column 1: The name/number of the cluster or group.
Column 2: The Right Ascension for epoch 2000.
Column 3: The Declination for epoch 2000.
Column 4: The redshift of the cluster.
Column 5: The distance in millions of light years assuming H=70km/s/Mpc.
Column 6: The 'richness' class of the cluster (for Abell clusters only).
Column 7: Additional names and notes.

Abell G, Corwin H, Olowin R, (1989), A catalogue of Rich Clusters of Galaxies, 
          Astrophys J Supp, 70, 1.
Struble M, Rood H, (1999), A compilation of redshifts and velocity dispersions for 
          ACO clusters, Astrophys J, 125, 35.
Garcia A, (1993), General study of group membership. II. Determination of nearby groups.
          Astron Astrophys Supp, 100, 47.
Giuricin G, Marinoni C, Ceriani L, Pisani A, (2000), Nearby optical galaxies: selection
          of the sample and identification of groups. Astrophys J, 543, 178.
Geller M, Huchra J, (1983), Groups of Galaxies. III. The CfA Survey. 
          Astrophys J Supp, 52, 61.
White R, Bliton M, Bhavsar S, Bornmann P, Burns J, Ledlow M, Loken C, (1999), Catalog 
          of nearby poor clusters of galaxies.  Astron J, 118, 2014.

A1656 - The Coma Cluster

The Coma cluster (A1656) is one of the most famous clusters of galaxies. It has received a huge amount of scientific research. This is partly because it is a very rich cluster containing thousands of galaxies. Another reason is that the Coma cluster lies a long way from the plane of our Galaxy (unlike the Perseus cluster, or the A3627 cluster) and it is largely unobscured by any gas and dust or any foreground stars.

The Coma cluster is dominated by two enormous elliptical galaxies. These are NGC4874 (right) and NGC4889 (left), they both have a diameter larger than 250 000 light years and they are much more massive than any galaxies in the Virgo supercluster. There is also one obvious foreground star in this image, HD112887, an eighth magnitude star 265 light years away - less than one millionth of the distance to the Coma cluster.

A1656 - from the Digitized Sky Survey
A map of the Coma cluster

This is a map of the central area of the Coma cluster. This map shows the positions of 118 of the brightest galaxies in the core of this cluster. It is immediately obvious that there are very few spiral galaxies, and no bright irregular galaxies. Nearly all of the galaxies here are elliptical and lenticular galaxies. One of the most popular theories on how elliptical and lenticular galaxies form is that they form from the merger of smaller galaxies. In the dense enviroment of the Coma cluster there have probably been many galaxy mergers over billions of years, and the result is a cluster with a very low number of spiral and irregular galaxies.

A map of the Coma cluster

This is a second map of the Coma cluster. This map has a width of four degrees (the previous map had a width of two-thirds of a degree). The blue points show the spiral galaxies and irregular galaxies, they are clearly more numerous in the outer parts of the cluster. This is very common in very rich clusters - the elliptical/lenticular galaxies are usually found in the centre, and the spiral/irregular galaxies are usually found in the outer regions.

The Scientific Study of the Coma Supercluster

The Coma supercluster has played a very important role in our knowledge of the structure of the universe. It was one of the first superclusters discovered. At the same time as Mihkel Jõeveer and Jaan Einasto in Estonia were suggesting that the universe was filled with superclusters and voids (see the page on the Perseus-Pisces supercluster), Stephen Gregory and Laird Thompson in the USA were also accumulating similar evidence. In 1978 they submitted a paper to the Astrophysical Journal entitled The Coma/A1367 supercluster and its environs. The paper contains a map of the supercluster showing how the two main clusters are contained within a larger supercluster. Laird Thompson has written a web page explaining about their Discovery of Superclusters and Voids.

In 1986, Valérie de Lapparent, Margaret Geller and John Huchra produced probably the most famous map of the structure of the universe ever made. In a paper called A slice of the universe they produced a famous map of the Coma supercluster. This picture was published in newspapers and magazines around the world because it showed the Coma cluster (looking like a strange stick-man figure) at the centre of a Great Wall of galaxies with a length of about six hundred million light years. It confirmed that the galaxies in the universe are arranged in sheets and walls surrounding large nearly-empty voids.

Since 1986, The Center for Astrophysics (CfA) at Harvard University has continued surveying this region of the sky. John Huchra has written a web page explaining about the survey.

The Coma cluster (A1656) has also played a very important role in our understanding of the universe. William Herschel discovered this cluster in 1785. In 1933, Fritz Zwicky submitted a paper to a Swiss Journal (Helvetica Physica Acta 6, 110) with the title: Die Rotverschiebung von extragalaktischen Nebeln, (The redshift of extragalactic nebulae). By studying the velocities of the galaxies in the cluster he showed that the cluster contained much more dark, invisible matter than visible matter. He later summarised his results in a paper (mainly in section 3) published in the Astrophysical Journal in 1937. Although he was correct, his research was ignored by other astronomers until the 1970's when astronomers began to realise that most of the matter in the universe must be of a dark, unseen type. The precise nature of this dark matter is still a mystery but it probably consists of enormous amounts of tiny subatomic particles which are present throughout the entire universe.

A huge amount of scientific research is directed at the Coma cluster. Only the Virgo cluster has received a similar amount of attention. In the five years from 1997 to 2001 approximately 125 papers were published about the Coma cluster, (almost identical to the number published about the Virgo cluster in the same period).

The Leo cluster (A1367) is also a very rich cluster, but because it is not as rich as the Coma cluster it is not studied as much. (Between 1997 and 2001 approximately 11 papers were written about this cluster).

A1367 - The Leo Cluster

Below is a picture of part of the Leo cluster. It is not as famous as the Coma cluster because it is slightly smaller and it contains fewer galaxies. The bright elliptical galaxy in the centre is NGC 3842 and the large spiral galaxy on the left is NGC 3861.

A1367 - from the Digitized Sky Survey
The nearest superclusters Back to the Neighbouring Superclusters page