Messier 39 – or NGC 7092 – is a large open star cluster in the constellation Cygnus, about 800 lightyears away.
Open star clusters are relatively young objects, in astronomical terms. M39 could be as young as 250 million years old. Some globular clusters, for example, are older than 11 billion years old.
M39 was catalogued by French astronomer Charles Messier in his famous Messier Catalogue of deep-sky objects in the 18th century.
M39 by Tom Howard, Crawley, Sussex, UK. Equipment: Nikon D7000, Meade 5000 127mm refractor, EQ6 mount.
Messier 39 can be seen with the naked eye under very dark conditions, and even binoculars and a small telescope will provide a good view of the cluster. Locate it in the sky near bright star Deneb, Alpha Cygni.
Below is a selection of images of Messier 39 captured by BBC Sky at Night Magazine readers and astrophotographers.
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Open Cluster – M39 by Danny Lee, Kent, UK. Equipment: Skywatcher Explorer 150p, EQ5 Pro GOTO mount, Nikon D40.
M39 by William McSorley, Leeds, UK. Equipment: SW 150P Reflector, EQ5 GoTo Mount, QHY8L cooled CCD, SW ST80, Philips SPC900 webcam.
M39 is 800 light years distant, and its stars are about 300 million years old. It has between 30 and 50 stars forming an attractive triangular shape.