Coma galaxy cluster (Abell 1656), optical image. The Coma cluster is a group of over 1000 galaxies that lies around 450 million light years from Earth in the constellation Coma Berenices. The two dominant members of the cluster are NGC 4889 (just below centre) and NGC 4874 (above and right of NGC 4889). The bright object at upper centre is an unrelated foreground star. These two galaxies are enormous, each some 300,000 light years in diameter, some three times the diameter of our Milky Way galaxy.