Open star clusters are widely distributed in our galaxy and represent a loose collection of stars which number from a few dozen to a few hundred stars and are weakly-held gravitationally. Perhaps the three most famous such open clusters are the Pleiades (M45) in Taurus, the Beehive (M44) in Cancer and the double cluster in Perseus. They are all characterized with a handful of hot and white prominent stars and nebular material surrounding these stars.

Note: The open cluster NGC 129 in Cassiopeia is a relatively young cluster whose age has been estimated to be around 77 million years old and as suggested by the predominance of bluish white stars in the image below. It is believed to be comprised of approximately 35 members stars which are detached from the background sky and without any concentration. Lying at a distance of 5,300 light-years away, the cluster is characterized with a handful of magnitude 8 and 9 stars with the remaining member stars generally being magnitude 10 and 11. NGC 129 lies at the midpoint between β-Cas (Caph, mag 2.26) and γ-Cas (mag 2.17) and is generally visible year-round owing to the fact it is effectively a circumpolar cluster. The cluster's discovery has been attributed to Herschel (1788) and is currently catalogued in multiple sources.