Clusters

Star Clusters are groups of stars that were formed at the same time. There are two basic types of star clusters: open clusters and globular clusters.

Open clusters usually are contained in a region less than 30 light years across. Some Open Clusters are clusters by appearance only (they just happen to be optically aligned, the stars were formed at different times).

A Sky Chart of the Pleiades open star cluster in Taurus

Globular clusters may contain hundreds of thousands of stars of the same origin. The name Globular is given due to their globe-like appearance. Globular cluster M13 in Hercules is one of the most impressive examples of a globular star cluster. Because of its brightness, it is a good target for small telescopes.

Globular cluster M13