Messier 50
Open cluster in the constellation Monoceros
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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]
| 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 |
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]
