| Messier 50 | |
|---|---|
| Open Messier 50 in Monoceros | |
| Observation data (J2000 epoch) | |
| Right ascension | 07h 02m 47.5s [1] |
| Declination | −08° 20′ 16″ [1] [a] |
| Distance | 2,870 ly (881 pc) [2] |
| Apparent magnitude (V) | 5.9 [3] |
| Apparent dimensions (V) | 16.0′ [3] |
| Physical characteristics | |
| Mass | > 285 M☉ [4] M☉ |
| Radius | 8.9 ly (2.73 pc) [4] |
| Estimated age | 158 [5] Myr |
| Other designations | M50, NGC 2323, Cr 124, C 0700-082, OCl 559 [6] |
| Associations | |
| Constellation | Monoceros |
Messier 50 or M 50, also known as NGC 2323 or the Heart-shaped Cluster, is an open cluster of stars in the constellation Monoceros. It was recorded by G. D. Cassini before 1711 and independently discovered by Charles Messier in 1772 [b] while observing Biela's Comet. It is sometimes described as a 'heart-shaped' figure or a blunt arrowhead. [3]
M50 is about 2,900 light-years away from Earth [2] and is near to but narrowly not estimated to be gravitationally tied to the Canis Major (CMa) OB1 association. [4] It has a core radius of 5.9 ly (1.8 pc) [7] and spans 17.8 ly (5.46 pc). [4] The cluster has 508 confirmed and 109 probable members – their combined mass is more than 285 M☉ , the mean stellar density would thus be 1.3 stars per cubic parsec. [4] It is around 140 million years old, [1] with two high-mass white dwarfs [8] and two chemically peculiar stars. [9]
Traditionally considered to be a single star cluster, in 2025 it was found to consist of two separate sub-clusters (NGC 2323-a and NGC 2323-b), making it a binary cluster. [5]