The Coma Cluster
Richer and denser than the Virgo Cluster and containing thousands of galaxies, the Coma Cluster (Abell 1656) is a telescopic wonderland that takes its name from its parent constellation, Coma Berenices. More than a hundred visible galaxies are packed into an area only a little greater than 3° in size; as many as 50 are visible through a 40-cm telescope. Exploring beyond its two dominant members is a challenge, though. At almost six times farther than the Virgo Cluster, its members are three or four times fainter. You can enjoy the sample tour I describe here with hardly more than a nudge of your telescope: The objects are contained in a single field of view of less than 1°.
The Coma Cluster lies is officially the brightest galaxy in the cluster at magnitude 11.5, but neighbouring has a slightly higher surface brightness and appears more brilliant to the eye. Both have significantly brighter cores surrounded by large, luminous halos, with NGC 4889 being noticeably more elongated. The two galaxies each anchor their own group of smaller, fainter companions and stand out strikingly among the many neighbours that cluster around them.
