The Double Cluster in Perseus, NGC 869 and NGC 884
Distance - 7,000 light years.
The two dense groupings of stars in the image above are known as open clusters [sometimes also known as a "galactic cluster"]. Open clusters are believed to originate in the same general area of space from the same local gas clouds.
The famous double cluster in Perseus was known in historic times (probably even pre-historically), and first cataloged by the Greek astronomer Hipparcos.
Both clusters are situated in the Perseus OB 1 association, and also only a few hundred light-years apart, at a distance of over 7000 light years. They are both quite young: NGC 869 is listed at 5.6, NGC 884 at 3.2 million years (Sky Catalog 2000); their hottest main sequence stars are of spectral type B0. They are approaching us at 22 (NGC 869) and 21 (NGC 884) km/sec, respectively.
December 9, 2012
1.5 hour exposure - 30 minutes per each color channel.
Blair Valley, Anza-Borrego Desert State Park, San Diego County, California
Optics - Takahashi Epsilon 160
Mount - Astro-Physics 1200 GTO
Camera - SBIG STL-11000M