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 6940 in Vulpecula has been estimated to be approximatelty 700 million years-old, thus making this bright and rich open cluster with over 100 member stars of intermediate age. The cluster lies approximately 2,500 light-years away and near the border border between Vulpecula and Cygnus. As indicated by the image below, the cluster is well detached from the background sky and without a central concentration with the reddish star HIP 101527 (FG Vul, mag 9.13) marking its approximate center (also note the impressive double star to the southwest with a separation of 4.5 arc-seconds). NGC 6940 was discovered by William Herschel in 1784.