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 7243 in Lacerta is a young cluster estimated to be around 115 million years-old and as suggested by the plethora of bright bluish stars in the image below. It is comprised of approximately 100 member stars and dominated by a handful of magnitude 8 and 9 stars and which includes an impressive bright double star system at its center (mags 9.25 and 9.68) whose separation is under 10 arc-seconds. It is well-detached from the backround sky with a slight horizontal concentration in a field spanning the apparent diameter of the full moon. The cluster has been estimated to lie at a distance of 2,635 light-years away. NGC 7243 was discovered by William Herschel in 1788.