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 1027 in Cassiopeia, discovered by William Herschel in 1787, is well-detached from the background sky and is comprised of 50-100 member stars with a wide range in magnitude which surround the bright central star SAO 12402 (mag 7.03). The cluster is characterized with an apparent diameter of twenty arc-minutes across, lies at a distance of 2,520 light-years away and is estimated to be only 160 million years old. The immediate area is characterized with faint nebulosity and hence for the brownish background sky in the image below. NGC 1027 is best observed using low-power magnifications during late fall and winter.