Globular Cluster Messier 80 (M80)

This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way Galaxy. Located about 32,600 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster are believed to have the same age (about 15 billion years) but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives. Astronomers have found a large population of "blue stragglers" in the core of the cluster. These stars appear to be unusually young and more massive than the other stars in a globular cluster. However, stellar collisions can occur in dense stellar regions like the core of M80, and in some cases, the collisions can result in the merger of two stars. This produces an unusually massive single star, which mimics a normal, young star. Based on the number of blue stragglers, the stellar collision rate in the core of M80 appears to be exceptionally high.