M53 + ngc5053 - Globular Clusters in Coma Berenices
Discovered 1775 by Johann Elert Bode.
Globular star cluster Messier 53 (M53, NGC 5024), top left in this image, is one of the more outlying globulars, being about 60,000 light years away from the Galactic center, and almost the same distance (about 58,000 light years) from out Solar system. At this distance, its apparent angular diameter of 13' corresponds to a linear diameter of roughly 220 light years. It is rapidly approaching us at a velocity given by Mallas as 112 km/s, by Harris as 79 km/s. M53 has a bright compact central nucleus of about 2' in diameter, although its stars are not very concentrated toward the center when compared to other globulars, and a gradually decreasing density profile to the outer edges.At only about 1 degree separation to the east (down and right in the image above), the faint and quite loose globular cluster NGC 5053 comes into the field of view, which is at roughly the same distance as M53 (53,500 light years), indicating that these clusters are also physically rather close together. NGC 5053 contains significantly less stars than M53, in particular doesn't have such a densely populated, compact bright center, so that its classification as globular was doubted in the past (now it was confirmed by spectroscopy).