what is this cluster?
It is a spherical collection of stars that orbits a galactic core.
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core.
some globular clusters have three main sequence tracks. this indicates UNANSWERABLE
wiki:7717054
Globular cluster [SEP] Introduction
A globular cluster is a spherical collection of stars that orbits a galactic core. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes, and relatively high stellar densities toward their centers. The name of this category of star cluster is derived from the Latin, "globulus"—a small sphere. Occasionally, a globular cluster is known simply as a "globular". Globular clusters are found in the halo of a galaxy and contain considerably more stars, and are much older than the less dense open clusters, which are found in the disk of a galaxy. Globular clusters are fairly common; there are about 150 to 158 currently known globular clusters in the Milky Way, with perhaps 10 to 20 more still undiscovered.