M39 in the Constellation Cygnus

The open star cluster M39 as photographed from our backyard last summer

As the Milky Way runs through Cygnus the Swan, M39 is seen against a background of stars.
The 50 or so stars that make up M39 probably condensed from a common molecular cloud some 270 million years ago.  The loose open cluster is approximately 7 light years across and can be seen, with individual stars resolved, through 7x50 mm. binoculars.

All the stars in M39 have been determined main sequence stars on the Hertzsprung- Russell diagram, with the brighter members being on the threshold of becoming red giant stars.

The whole cluster has a proper motion of 0.024 seconds per year and is moving towards us at 28km/sec.



Hertzsprung- Russel Diagram (Credit Wikipedia)