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 1981 illustrated below lies 0.5 degrees north NGC 1977 (Running
Man Nebula) and slightly over one degree north of M42-M43 (Orion Nebula). It is comprised of approximately 20 member
stars lossely scattered across a field measuring 0.5° by 0.5° and with at least eight bright stars ranging in magnitude
from 6.5 to 8.1 dominating the field of view. The cluster is approximately 1,200 light-years away with an apparent
diameter of 10 light-years across. Although no estimates as to the age of this cluster exist, other clusters within Orion
(NGC 1976 and Collinder 69-70) have been dated to be only 10 to 13 million years old. The nebulosity in the lower portion
of the cluster is from the reflection/emission nebula NGC 1977. The cluster is best viewed during winter and can easily
be located using binoculars just to the south of Orion's belt.
Please click on the image below to display in higher resolution (1200 x 900)