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 7092 is the brightest and most populous of the many open clusters one can encounter in Cygnus with a magnitude of 4.6. Dominated by multiple member stars ranging in magnitude from 7 to 8, this cluster lies approximately 825 light-years away and spans about 7 light-years. As revealed by the image below, the presence of various bright blue stars indicates that this cluster is not very advanced in age and is estimated to be approximately 230 million years old. The cluster was first discovered by Le Gentil in 1750 and later first observed by Messier in 1764. However, some believe the cluster was known and observed in antiquity by Aristotle. The cluster lies approximately nine degrees from Deneb (á-Cyg, mag 1.33) and can be visible with the naked eye under dark skies. Messier 29 (NGC 6913) is the other Messier open cluster in Cygnus. Both clusters are best observed using low magnifications during summer and early fall where they are placed directly overhead when looking due east.
Please click on the image below to display in higher resolution (1200 x 900)
M39, Cr 438, Mel 236
III 2 m
RA / Dec:
21h 31m 57s /
48° 25' 15"
31' x 31'
Aug 20-21, 2011
21:50 - 00:15 UT+3
AP 305/f3.8 Riccardi-Honders
AP 1200GTO GEM
SBIG LRGB filters
1.25" per pixel