Globular cluster

A globular cluster is a spherical bundle of stars that orbits a galaxy as a satellite. Globular clusters are very tightly gravitationally bound, which gives them their spherical shape, and extremely dense (in relative terms) towards their core.

Globular clusters are usually composed of hundreds of thousands of old stars. They are are fairly numerous; there are about 150 currently known globulars of the Milky Way (with perhaps 10-20 more undiscovered)