Star cluster is a group of stars detained jointly
since regards the result of gravitation. Star clusters are classified into two
groups: open clusters, which have no definite shape, and globular clusters,
which are spherical or nearly spherical. The open consist of a few hundred
young stars, while globular clusters contain more than a thousand times that
amount, and are generally very old stars. Globular clusters form a halo around
our galaxy, the Milky Way, while the open is located in the spiral arms. Open
clusters are much more numerous than globular: about 1,000 are known in our
galaxy and there are only 140 globular.
