NGC 2323

Messier 50 (NGC 2323) is an open star cluster in the constellation Monoceros (the Unicorn), located approximately 3,000 light-years from Earth and spanning about 20 light-years across. It was possibly first discovered by Giovanni Cassini around 1711, making it one of a handful of Messier objects with pre-Messier records; Charles Messier catalogued it independently on April 5, 1772. NGC 2323 contains some 200 stars and is estimated to be between 78 and 100 million years old — a relatively young cluster in which the hottest original members have barely begun to evolve off the main sequence. More fanciful observers have described its overall star pattern as heart-shaped.

NGC 2323 lies in a region of the Milky Way between Sirius and the three stars of Orion's Belt, placing it in a rich swath of the winter sky. Its stellar population is dominated by hot blue-white stars, reflecting its youth, with a scattered handful of brighter orange giants that have already evolved off the main sequence. The cluster is moderately concentrated, with a slightly denser core fading into a more diffuse outer region. A bright, reddish-orange star near the center of the cluster — a K-type giant — provides a striking color contrast against the blue-white majority.

In binoculars M50 appears as a moderate-brightness condensation in the rich winter Milky Way; a small telescope resolves it into a compact, attractive gathering of roughly 50 brighter stars over a granular background of fainter members. This approximately true-color image was assembled from twelve BVR exposures taken in September 1997 at the Burrell Schmidt telescope of Case Western Reserve University's Warner and Swasey Observatory on Kitt Peak.