Globular Cluster

Globular Cluster, compact, spherical group of stars, containing many thousands or even millions of stars.

Astronomers have found more than 200 globular clusters in the Milky Way Galaxy (the earth’s galaxy). Most galaxies contain globular clusters and some galaxies contain thousands of such clusters. Most of the known globular clusters in the Milky Way move around the center of the galaxy in orbits that take them far outside the Milky Way. By finding the center of their orbits, the American astronomer Harlow Shapley of Harvard University located the Milky Way’s center in 1918.

Globular clusters are the oldest structures associated with our galaxy. They contain only Population II stars—the oldest stars in the universe. All globular clusters in the Milky Way and the neighboring Andromeda Galaxy seem to be about the same age, suggesting they were created by conditions within galaxies while the galaxies were young.

The diameters of globular clusters average about 50 light-years. The stars within a cluster are very densely packed near its center and may be only a few billion kilometers away from each other.