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 . ... 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. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...