Globular clusters are massive assemblies of stars.
More than 100 such clusters are known in the Milky Way galaxy and most of them harbor several million stars. Globular clusters are among the oldest objects known, with estimated ages of 11 to 15 billion years. All stars in a globular cluster were formed at nearly the same moment, and from the same parent cloud of gas and dust. The original chemical composition of all stars is therefore the same. Such stars have about the same mass as our Sun and, like the Sun, they evolve very slowly.