NGC 3201

NGC 3201 (aka Caldwell 79) is a globular cluster with a radius of 40 ly and a presumed age of more than 10 gigayears (one determination is 10.24 Gy). It is of interest because a probable black hole has been identified, using the radial velocity of a star that indicates it is orbiting something unseen and very massive (more mass than would be possible for a neutron star, white dwarf or red dwarf). It is assumed that globular clusters generally host multiple stellar-mass black holes, simply based upon the large number of resident stars, but currently they can only be identified when specific clues are available, such as in this case.