Globular star clusters collections of thousands to millions
of stars and are among the oldest objects
in the Universe. These star clusters are almost spherical
in shape and are held together by gravity.
There are more than 120 such clusters known
in the Milky Way, yet the nearby Andromeda galaxy, M31,
has more than 400, and some giant elliptical
galaxies contain well over a thousand. The oldest
globuar clusters trace the formation histories of the
haloes of galaxies. New globular clusters are thought to
form when galaxies merge.
Star Clusters in M31