M39: Open Cluster in Cygnus.

Lying just at the limit of human perception is a picturesque starfield containing one of the larger open clusters on the northern sky. Spanning an angle larger than the Moon , M39's relatively few stars lie only about 800 light years distant toward the constellation of Cygnus . The above picture of M39 is a mosaic of 33 images taken by the WIYN telescope on Kitt Peak in Arizona , USA . The stars in M39 are all about 300 million years old, much younger than the 5000 million years of our Sun . Open clusters, also called galactic clusters , contain fewer and younger stars than globular clusters . Also unlike globular clusters, open clusters are generally confined to the plane of our Galaxy .