Editing Star cluster (section)

{{short description|Group of stars}}
[[File:M44 47x300s-10°C O30 G0 PM RGB 03032022.jpg|thumb|upright=1.4|[[Messier 44]], a cluster in the [[constellation]] of [[Cancer (constellation)|Cancer]]]]

A '''star cluster''' is a group of [[star]]s held together by [[self-gravitation]]. Two main types of star clusters can be distinguished: [[globular cluster]]s, tight groups of ten thousand to millions of old stars which are [[gravitation]]ally bound; and [[open cluster]]s, less tight groups of stars, generally containing fewer than a few hundred members.

As they move through the [[galaxy]], over time, open clusters become disrupted by the gravitational influence of [[giant molecular cloud]]s, so that the clusters we observe are often young. Even though they are no longer gravitationally bound, they will continue to move in broadly the same direction through space and are then known as [[stellar association]]s, sometimes referred to as ''moving groups''.  Globular clusters, with more members and more mass, remain intact for far longer and the globular clusters we observe are usually billions of years old.

Star clusters visible to the naked eye include the [[Pleiades]] and [[Hyades (star cluster)|Hyades]] open clusters, and the globular cluster [[47 Tucanae]].