This Hubble Space Telescope image shows M80, one of the densest of the 147 known globular star clusters in the Milky Way galaxy. This cluster is located about 28,000 light-years from Earth in the constellation Scorpius. It contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are extremely useful for studying the evolution of stars, because all of the stars in the cluster have the same age, but cover a range of different masses. The stars in M80 are believed to be about 15 billion years old.