Messier 39 (NGC 7092): A Larger Cluster of Straggling Stars in Cygnus

Messier 39 is an open star cluster in the constellation of Cygnus, best viewed in summer or late autumn. The astronomer Guillaume Le Gentil first recorded the stellar object in 1749 with Charles Messier adding it to his collection almost 20 years later in 1764.

M39 and M29 are the sole Messier objects in Cygnus. To fully appreciate M39, one should use binoculars or low magnification on a telescope as the cluster’s diameter in the sky is nearly the same as the moon. M39 lies only 800-1000 light years away, making it one of the nearer star clusters to us.

My Observations

A handful (7-10) of stars stand out brightly in contrast to a swarm of Milky Way faint stars in the background. Upon observing this cluster for the second time in my life (on October 8, 2021), I have to say this is becoming one of my favorite clusters. The bright white and blue stars are like prominent jewels. The 32mm eyepiece works well with this cluster.

I also observed M39 on October 8, 2021, at 8:40 p.m.

Key Stats

Constellation	Cygnus
Best Viewing	Autumn
Visual Magnitude	+4.6
Absolute Magnitude	-2.9
Distance from Earth	900 ly
Diameter	9 ly
Apparent Size	29 arcmin
Milky Way Location	Orion Spur
My Viewing Grade	A-

Historical Observations

Charles Messier on the evening of October 24 to 25, 1764

“I observed a cluster of stars near the tail of Cygnus: One distinguishes them with an ordinary (nonachromatic) refractor of 3 and a half feet; they don’t contain any nebulosity; its extension can occupy a degree of arc. I have compared it with the star Alpha Cygni, and I have found its position in right ascension of 320d 57′ 10″, and its declination of 47d 25′ 0″ north.”

Sources and Notes

Photo of M39 is by Christian van Endern. The photo is shared and licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Quote from Charles Messier sourced from https://www.messier.seds.org/