Abstract
Stars form in clusters. The most common star clusters form in the discs of galaxies; they are young, not very concentrated and open. They dilute and break up rapidly. Globular clusters, on the other hand, are much richer, more concentrated and strongly bound by gravity. They form under violent conditions during galaxy interactions, when huge quantities of gas collide and compress. In our galaxy, most globular clusters have been gradually destroyed by interaction with the disk, and by tidal tails that have accumulated in the stellar halo.
