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: Although estimates vary dramatically, open cluster NGC 188 has been estimated to be anywhere from 5 to 24 billion years old, thus making this widely dispersed cluster one of the oldest open clusters known in the Milky Way. With slightly over 100 member stars lying approximately 5000 light-years away, the cluster lies three degrees from the north celestial pole and, technically, falls within the constellation of Cepheus. The cluster's discovery has been attributed to Herschel (1831) and is currently catalogued in multiple sources. Being effectively a circumpolar cluster, its observation is not dependent on season and/or time.