Messier 39 (M39)

Also Known as: NGC 7092, Collinder 438

Object Type: Open Cluster

Constellation: Cygnus

Distance from Earth: 824.4 light years

Apparent Magnitude: 5.5

Coordinates: RA 21H 31M 42S DEC 48 deg 25 min 0 sec

Actual Size: 28 light years in diameter

Apparent Dimensions: 32 arc-minutes

Discovered by: M39 may have been discovered by Guillaume Le Gentil in 1750 and possibly even the Greek philosopher Aristotle as a comet in 325 BC.
Charles Messier catalogued the cluster on October 24, 1764. English astronomer John Herschel catalogued the cluster as h 2126 in September 1829 and later added it to the General Catalogue as NGC 4681. Herschel described M39 as a “cluster; very large; very poor; very little compressed; stars between 7th and 10th magnitude.”

Description: M39 is a large open cluster with an apparent diameter larger than the full Moon.
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.
Messier 39 is one of the nearest Messier objects to Earth. Only the Pleiades (M45), Winnecke 4 (M40), the Beehive Cluster (M44), and possibly the Ptolemy Cluster (M7) are closer to us.
Messier 39 is classified as either Trumpler type III,2,m or III,2,p. This means that it is detached from the surrounding star field but with no central concentration (III), that the stars in the cluster have a moderate range in brightness (2), and that the cluster is either moderately rich, with 50 to 100 stars (m) or poorly populated (p), with fewer than 50 stars.

Messier 39 is located about 9 degrees to the east and a bit north of the bright star Deneb, Alpha Cygni.
The cluster’s apparent size is 32 arc minutes, making it larger than the full Moon, which means that M39 is best observed in binoculars and small telescopes at the lowest magnifications.
The cluster can be resolved in 7x50 binoculars which reveal a triangular shape.

The best time of the year to observe M39 is the summer months (June-August).

Platesolve

M39 Open Cluster

Imaging Details
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