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 2422 is one of three major open clusters in Puppis (along with M46 and M93). The cluster is very young with an estimated age of only 78 million years old. Its apparent diameter is similar to that of the full moon, spanning 12 light-years across and at a distance of 1,600 light-years. It is comprised of approximately 50 member stars including several bright members whose magnitude ranges from 9 to 10 and includes three yellow giants (SAO 135668 at mag 8.19, HIP 40362 at mag 9.47 and GSC 4855:1359 at mag 8.2). The cluster was first discovered by Giovanni Batista Hodierna in 1654 and later independently rediscoverd by Charles Messier in 1771. The cluster lies to the east of Sirius and within the immediate vicinity of M46. NGC 2422 is best observed in winter as it approaches the southern meridian just before midnight.