Globular Cluster M22 from CFHT
The globular cluster M22 , pictured above , contains over 100,000 stars. These stars formed together and are gravitationally bound. Stars orbit the center of the cluster, and the cluster orbits the center of our Galaxy . So far, about 140 globular clusters are known to exist in a roughly spherical halo around the Galactic center . Globular clusters do not appear spherically distributed as viewed from the Earth, and this fact was a key point in the determination that our Sun is not at the center of our Galaxy . Globular clusters are very old . There is a straightforward method of determining their age , and this nearly matches the 13.7 billion-year age of our entire universe .