Coma Cluster
| Coma Cluster | |
|---|---|
Map of the central part of the Coma Cluster | |
| Observation data (Epoch ) | |
| Other designations | |
| Abell 1656 |
The Coma Cluster (Abell 1656) is an huge galaxy cluster and the prototypical rich cluster with over a thousand member galaxies known. Besides these, some thousands of smaller systems and a lot of dark matter is supposed.
Structure of the galaxy cluster
The Cluster's mean distance from Earth is 140 Mpc (450 million light years). Its 10 brightest spiral galaxies have apparent magnitudes of 12-14 mag which already can be made out by amateur telescopes larger than 20 cm.
The image shows the central region, dominated by two giant Ellipticals and therefore is of type B (binary core): The two central cD galaxies, NGC 4874 and NGC 4889, are truly extraordinary, each with a diameter of approximately 300 000 light years - three times that of our own galaxy.
Around the galaxies is a cloud of very hot gas plasma which shows up both in X-ray observations and also in Sunyaev-Zeldovich observations with the Very Small Array. The mass of this cloud of gas is much higher than the mass of the stars in all the galaxies in the cluster.
Cluster members and foreground galaxies
As is usual for clusters of this richness, the galaxies are overwhelmingly elliptical and S0 galaxies, with only a few spirals of younger age, and many of them probably near the outskirts of the cluster. Most of the objects in the picture above are galaxies; only the very bright objects with diffraction spikes and the smallest circular dots are foreground stars of our own Galaxy.
The large dimension of the Galaxy cluster was detected not till than in the 1950ies, mainly by astronomers of the Mount Palomar observatory. But in the cluster's foreground, some bright single galaxies are known for more than 200 years and about 10 times closer to our milky way. Most of them are Messier objects, e.g. M85, M88, M98, M99 and M100 with distances of approximarely 20 to 40 million light years.
Another well known galaxy cluster is the Virgo Cluster, located in the neighbouring constellation Virgo some degrees to the south. Although many of its member galaxies have been known since the time of Messier, the fact that these galaxies are associated was not discovered until the middle of the 20th century. The Virgo contains some 3000 - 4000 members.
See also:
References
- The dynamical state of the Coma cluster with XMM-Newton
- Very Small Array observations of the Sunyaev-Zel'dovich effect in nearby galaxy clusters
External links
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