the double cluster
the double cluster Back to Index Page Previous Image Next Image
Recorded by early observers as far back as Hipparchus, the great Double Cluster of Perseus is one of the more popular deep-sky objects in all of the heavens. The open star clusters NGC 869 and NGC 884 combine to form a most distinct faint, fuzzy glow that is easily visible to the unaided eye. In a pair of common binoculars or small telescope, however, the individual clusters simply come alive with an abundance of stars flowing in every direction and spanning more than one degree of sky! Modern scientific measurements place the age of the Double Cluster at just over 10 million years, which is fairly typical for such objects. One of the more distinct features of the clusters is the proliferation of rather massive, hot blue-supergiant type stars, which appear to dominate the image above. However, this is merely a small sampling of the actual brilliance of the brighter members, as the entire cluster area is reddened by interstellar extinction by an average of two full magnitudes. This extinction is caused by the dense strands of dust located between us and the cluster members, and it can be seen in this image as distinct voids or "holes" along the outer edges of the clusters. During the winter, when I get tired of straining my eyes attempting to glimpse objects at the edge of visibilty, I often turn my 17.5-inch Dob towards the Double Cluster using a 35mm Panoptic. One of my favorite things to do is hunt down the many red stars that can be seen in stark contrast against the myriad of blue diamonds. Also of note is the peculiar nature of the double star strands located just south of the core of NGC 884 (the one on the left in this image). It is suspected that more than 700 members inhabit the two clusters, which appear to contain in total more than 7000 times the mass of our very own Sun! Image taken with homemade 8-inch f/5.4 astrograph and SBIG STL-11000XM. RGB image composed of 30 minutes each R,G,B. Please click on the image above for the high resolution version.