Messier 39 is a large open cluster in Cygnus.

It has an apparent size of 31 arcminutes, which is larger than the full Moon, and an apparent magnitude of 4.6. It is possible that the cluster was noted by Aristotle in 325 B.C.E., although most credit its discovery to Charles Messier in 1764.

At an estimated distance of 800 light-years, its true size in space would be 7.5 light-years in diameter.

Like most open clusters, its stars are relatively young, with an estimated age of between 230 million and 300 million years.

M39 is a very sparse and loose open cluster that contains 30 stars. a dozen of these are brighter than 9th magnitude with the brightest being magnitude 6.57 with a spectral-type of B. Most of the other brightest stars are spectral-type A.

North is to the top in the above image.

Messier 39 Catalogs: M39, NGC 7092 Object Type: Open Cluster Magnitude: 4.6v Size: 31' Constellation: Cygnus Image Field Centered At: RA: 21h 31m 58s Dec: +48° 28' 08"