Messier 39 (M39) is a large open cluster located in the constellation Cygnus, the Swan.
The cluster has an apparent magnitude of 5.5 and lies at a distance of 824.4 light years from Earth. It has the designation NGC 7092 in the New General Catalogue.
Messier 39 has an estimated age of 200 to 300 million years. All its confirmed members are still on the main sequence, still burning hydrogen in their core, and have yet to evolve into red giants.
Messier 39 is a relatively loose cluster with 30 confirmed members occupying an area about 7 light years in diameter. The cluster is approaching us at 28 km/s.
Facts about M39 by Keith Turnecliff
M39 is also known as NGC7092.
The cluster is slightly larger than a full moon, so well suitable for binocular users.
The best time of year to observe M39 is in the summer months, when Cygnus is high overhead.