NGC 381 is an open cluster of stars in the northern constellationofCassiopeia, located at a distance of approximately 3,120 light-years from the Sun.[2] Credit for the discovery of this cluster was given to Caroline Herschel by her brother William in 1787, although she may never have actually seen it.[7]
| NGC 381 | |
|---|---|
 | |
| Observation data (J2000 epoch) | |
| Right ascension | 01h08m 19.9s[1] |
| Declination | +61° 35′ 02″[1] |
| Distance | 3,120 ± 300 ly (957 ± 93 pc)[2] |
| Apparent magnitude (V) | 9.3[3] |
| Apparent dimensions (V) | 6′[1]or7′[3] |
| Physical characteristics | |
| Mass | 32.4+45.2 −18.9[4] M☉ |
| Radius | 15 ly[5] |
| Estimated age | 316+39 −34[2] |
| Other designations | Collinder10[6] |
| Associations | |
| Constellation | Cassiopeia[3] |
| See also: Open cluster, List of open clusters | |
This is a Trumpler class III 1 m cluster of intermediate age,[1] estimated at 316 million years. This class indicates the cluster is relatively weakly concentrated, with a small brightness range and an intermediate richness of stars. A total of 350 probable members have been identified, down to 20th magnitude,[2] and the cluster contains about 32 times the mass of the Sun.[4] The cluster has a core angular radius of 2.99′±0.93′ and an outer cluster radius of 5.6′±0.1′.[2] It has a physical tidal radius of 15 ly (4.7 pc).[5]Nogiant stars have been discovered in this cluster.[1] Four candidate variable stars have been found in the field of NGC 381; one of which is a suspected cluster member.[8] The eclipsing binary OX Cassiopeiae was once thought to be a member, but is now known to be a background star system.[9]