Coma Star Cluster

Melotte 111 or the Coma Berenices star cluster, is an open star cluster in the constellation Coma Berenices, which can be observed with the naked eye. The cluster forms with its 37 individual stars the main part of the constellation Coma Berenices. Moreover, it was the impression of this cluster with the naked eye probably its name to the constellation.

The expansion of the star cluster is about 4.5 °, respectively - at a distance of 288 light years - about 20 light-years. The brightest star of the cluster is γ Com like with a brightness of 4.3, the total brightness of the cluster is about 1.8 mag. The heap contains no stars that are weaker than 10.5 mag. One possible explanation for this is that the smallest members of this cluster have already escaped.

Due to its size and brightness of this star cluster has been known since ancient times and has been cataloged for the first time by Ptolemy. Like many star clusters that have a very small distance from the Earth, and therefore a large apparent diameter possess (eg, the Ursa Major group or the Hyades ), he was not included in the modern standard catalogs Messier, NGC and IC. Only P. J. Melotte took the pile of 1915 in his catalog of open star clusters. Under the name of the cluster Cr 256 is also to be found in the catalog of Per Collinder.

The cluster is called a bunch of movement, that is, the stars all have a similar proper motion (on average -12.4 mas in right ascension and -9.4 mas in declination ). Since the mean of the proper motions, however, almost exactly tangent is (mean radial velocity of -1.17 km / s), allows this movement (as opposed to well-known example of the Hyades ) not an easy determination of distance by the star Tromp Aral Laxe.