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: Open cluster NGC 1647 in Taurus depicted below is a bright and rich open cluster comprised of over 100 member stars which are well interspersed and detached from the background sky. The cluster is dominated by many mag 8 and mag 9 stars with its brightest star being mag 8.3 (SAO 94100). The cluster spans 40 arc-minutes in diameter, lies 1760 light-years away and has been estimated to be about 145 million years-old. The cluster is best observed using low magnifications (50-100x) during winter when it is directly overhead and can be found to lie just to the northeast of Aldebaran (α-Tau, mag 0.87). NGC 1647 was discovered by Friedrich Wilhelm Herschel (1738-1822) in 1784.

Note: There exist faint traces of nebulosity around the brighter stars and which may be misinterpreted as light pollution.