stellar cluster

A stellar cluster or star cluster (sometimes abbreviated SC) is a general term including both globular clusters and open clusters, consisting of groups of stars near each other, with other similarities that suggest their formation is from a single cloud. The distinction between globular versus open clusters is that the former are tightly bound by gravity and the latter is more loosely bound.

A young stellar cluster (YSC) is one showing signs of being young, i.e., ultraviolet indicating early stars. In surveys for finding stellar clusters, possible YSCs have been termed YSCCs for young stellar cluster candidates. An embedded cluster (EC) is a cluster within a gas cloud, i.e., one still residing in the cloud of its formation.

A stellar association is looser than an open cluster but shows signs of common origin, such as similar age and metallicity. Often it is a moving group (aka kinematic group), a group of stars that are generally moving together. Such groups are presumed to be the remnants of stellar clusters, a notion supported by the fact that such groups often show older stars than typical of open clusters.