Messier 39 is a relatively young open cluster estimated to be around 250 to 300 million years old. It contains about 30 bright blue-white stars spread over a wide area, giving it a coarse and loose appearance. The cluster is easily visible in binoculars, and even under dark skies, it can be detected with the naked eye as a faint hazy patch. For astrophotographers, M39 is a rewarding target due to its large size and placement in the rich star fields of the Milky Way.
Names and Catalog numbers
- Pyramid Cluster
- Messier 39
- NGC 7092
- Melotte 236
- Collinder 438
Position and the cosmic neighborhood
Messier 39 lies in the northern part of the constellation Cygnus, about 9° east-northeast of the bright star Deneb (Alpha Cygni). It is embedded in one of the most photogenic regions of the Milky Way, full of faint background stars that enhance its visual appeal in wide-field astrophotography. Nearby celestial landmarks include the Cocoon Nebula (IC 5146) and the open cluster NGC 7082, making this region a rich target area for deep-sky imaging. Observers often frame M39 within the Cygnus star fields to capture its contrast against the dense galactic background.
Nice to Know
- Messier 39 was discovered by Guillaume Le Gentil in 1749, 15 years before Charles Messier added it to his catalog.
- The cluster’s distinctive triangular formation has inspired the nickname “Pyramid Cluster.”
- M39 includes several binary star systems and a handful of chemically peculiar stars.
- The cluster’s stars are gradually dispersing as they drift apart over millions of years due to gravitational interaction with the galaxy.
Brightness, distance and size
Messier 39 shines with an apparent magnitude of about 4.6, making it easily visible without optical aid in dark skies. Its distance ranges from approximately 800 to 1,010 light-years from Earth. The cluster spans around 7 light-years across, corresponding to an angular size of roughly 29 to 32 arcminutes—about the same apparent size as the full Moon. This broad extent makes M39 an ideal object for astrophotography with short focal length telescopes or camera lenses capturing large portions of the Cygnus Milky Way.
