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 2301 in Monoceros illustrated below is within a few degrees of two other bright and large open clusters (NGC 2286 and 2324) and to the immediate west of δ-Monocerotis (mag 4.14). Lying at a distance of 2,450-2,840 light-years away depending on the source, NGC 2301 is estimated to be 160 million years old. Comprised of approximately 100 member stars spanning approximately 14 arc-minutes in diameter, this cluster is well detached from the background sky owing to the fair number of bright member stars running vertically. NGC 2301 is best observed during winter and early spring when it is above the southern meridian at the end of astronomical twilight and thereafter.