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 Melotte 15 at the center of the expansive emission nebula IC 1805 (Heart Nebula) in Cassiopeia was discovered by British astronomer Philibert Jacques Melotte (1880-1961) and which was published in 1915 along with his catalog of 245 deep-sky objects comprised of open and globular clusters identified while studying the Franklin-Adams plates. Melotte 15 is comprised of OB-association hot young stars spanning approximately 30 light-years across and which illuminate and sculp the excited ionized hydrogen in the immediate area. The cluster lies 7,500 years away and has been estimated to be quite young at a mere 1.5 million years old. A small sample of the stars which comprise Melotte 15 are characterized with a mass fifty times that of the Sun.
Please click on the image below to display in higher resolution (1200 x 900)
IC 1805, Col 26
II 3 m
RA / Dec:
02h 32m 42s /
61° 27' 48"
Oct 18-19, 2012
23:10 - 03:30 UT+3
AP 305/f3.8 Riccardi-Honders
AP 1200GTO GEM
SBIG LRGB filters
Baader H-a 7nm
1.21" per pixel