... M39: Open Cluster in Cygnus . ... Spanning an angle larger than the Moon , M39's relatively few stars lie only about 800 light years distant toward the constellation of Cygnus . ... 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 . ... Publications with keywords: open cluster - Cygnus . Publications with words: open cluster - Cygnus . ...