Open Cluster Messier 50

Messier 50
Messier 50: Section of the STScI Digitized Sky Survey [147]


The star cluster was discovered in 1709 by the Italian astronomer Giovanni Cassini. When Charles Messier observed Comet Biela on April 5, 1772, he encountered the star cluster again. In order to avoid confusing such nebulous stars with comets in the future, he added it as the 50th object on his list. The German astronomer Johann Bode found the star cluster again on February 12, 1774 when he was looking for Cassini's observation.

Physical Properties

M 50 is of the Trumpler type II3m and about 10 minutes of arc in diameter. A few further outlying stars reach up to 20x15 arc minutes. About 200 stars belong to the cluster. Robert Burnham Jr. describes «curving arcs of stars make a heart-shaped outline, nicely highlighted by a single reddish star about 7' south of the center of the cluster». Distance measurements give a distance of 881 pc to 902 pc (2873 to 2942 light years). The true diameter of the cluster is therefore about 9 light years. [4, 145, 196]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 2323
TypeOCL (II3m)
Right Ascension07h 02m 47.8s
Declination-08° 22' 33"
Diameter15.00 arcmin
Visual magnitude5.9 mag
Dreyer Description! Cl, vL, Ri, pC, E, st 12…16
IdentificationM 50, OCL 559

Finder Chart

M 50 lies in the constellation Monoceros (unicorn). It is located approximately on the first third of the line Sirius (α Canis Majoris) - Procyon (α Canis Minoris), or approximately in the middle of Sirius (α Canis Majoris) - δ Monocerotis. The best time for observation is November to March.

Chart Messier 50
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]


4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
196Celestial Atlas by Curtney Seligman; (2020-12-28)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)