[3][9][10] Its ten brightest spiral galaxies have apparent magnitudes of 12–14 that are observable with amateur telescopes larger than 20 cm.

[16][17][18] The Coma Cluster is one of the first places where observed gravitational anomalies were considered to be indicative of unobserved mass.

The distribution of dark matter throughout the cluster, however, is poorly constrained[clarification needed].

[21] An extended X-ray source centered at 1300+28 in the direction of the Coma cluster of galaxies was reported before August 1966.

[24] As the source is extended, with a size of about 45', this argues against the possibility that a single galaxy is responsible for the emission.