Explanation:
Lying just at the limit of
human perception is a
picturesque starfield containing one of the larger
open clusters on the northern sky.
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 above picture of
M39 is a mosaic of 33 images taken by the
WIYN telescope on
Kitt Peak in
Arizona,
USA.
The stars in M39 are all about 300 million years old,
much younger than the 5,000 million years of our
Sun.
Open clusters, also called
galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike globular clusters,
open clusters are generally confined to the
plane of our Galaxy.
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