Coma Cluster of galaxies
Almost every object you see in this image, especially in its central part, is a galaxy. The Coma Cluster of galaxies (Abell 1656) is one of the richest galaxy clusters known, located in the faint constellation Coma Berenices, visible in medium to large amateur telescopes. The Coma Cluster contains over 1,000 identified galaxies. Along with the Leo Cluster (Abell 1367), it is one of the two major clusters comprising the Coma Supercluster, which is just a small part of the large structure of the Universe .
The main body of the Coma cluster has a diameter of about 25 million light-years, but enhancements above the background can be traced out to a supercluster of a diameter of about 200 million light-years. The central part of Coma Cluster of galaxies covers a roughly circular area about a degree and a half across (9 times the area of a full moon). An old but beautiful name for this region of sky is the Realm of the Galaxies. The Coma cluster is flying away from us at the rate of about 6,900 km/second .
The Coma cluster is significant historically as the first place where there was an indication of dark matter in addition to the calculated visible masses of the galaxies. In 1933 Fritz Zwicky used calculated masses and observed speeds to conclude that the galaxies were moving too fast to be accounted for by the visible masses of the galaxies .
The cluster's mean distance from Earth is 321 million light years, which means its light is reaching us now and originated at period of time when Earth was in the midst of Carboniferous geological period, well before first dinosaurs ruled the Earth (when Pangea supercontinent begun to form and massive swamps cooked, over tens of millions of years, into today's vast reserves of coal and natural gas, when Oxygen made up a much higher percentage of the earth's atmosphere than it does today, fueling the growth of terrestrial megafauna, including dog-sized insects) [3, 9].
The central region is dominated by two supergiant elliptical galaxies: NGC 4874 and NGC 4889. Most of the galaxies that inhabit the central portion of the Coma Cluster are ellipticals. Both dwarf and giant ellipticals are found in abundance in the Coma Cluster, although majority belongs to dwarf galaxies .
NGC 4874 (Coma A) is a giant elliptical galaxy, about ten times larger than the Milky Way. It was discovered by William Herschel in 1785, who catalogued it as a bright patch of nebulous feature. The second-brightest galaxy within the Coma Cluster, it is located at a distance of 350 million light-years from Earth. The galaxy is surrounded by an immense stellar halo that extends up to one million light-years in diameter. It is also enveloped by a huge cloud of interstellar medium that is currently being heated by action of infalling material from its central supermassive black hole at the centre of the Coma Galaxy Cluster. With its strong gravitational pull, NGC 4874 is able to hold onto more than 30 000 globular clusters of stars, more than any other galaxy that we know of, and even has a few dwarf galaxies in its grasp.
NGC 4889 (also known as Coma B) is a supergiant elliptical galaxy, also discovered in 1785 by William Herschel. The brightest galaxy within the Coma Cluster, it is located at a median distance of 308 million light years from Earth.
NGC 4921 spiral galaxy is very unusual one; it was imaged by HST and described in video  showing an extraordinary rich background of more remote galaxies stretching back to the early Universe.
In the low right corner there is bluish irregular galaxy, NGC 4789A, which contains a huge amount of atomic hydrogen and has a very large ratio of dark matter to ordinary matter but, for some reasons, has a very low star formation rate .
Imaged from Negev Desert
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