NGC 381

NGC 381 is an open cluster of stars in the northern constellation of Cassiopeia, located at a distance of approximately 3,120 light-years from the Sun.[3] 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)
ConstellationCassiopeia[1]
Right ascension01h 08m 19.9s[2]
Declination+61° 35′ 02″[2]
Distance3,120 ± 300 ly (957 ± 93 pc)[3]
Apparent magnitude (V)9.3[1]
Apparent dimensions (V)6′[2] or 7′[1]
Physical characteristics
Mass32.4+45.2
−18.9[4] M☉
Radius15 ly[5]
Estimated age316+39
−34[3]
Other designationsCollinder 10[6]

This is a Trumpler class III 1 m cluster of intermediate age,[2] 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,[3] 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′.[3] It has a physical tidal radius of 15 ly (4.7 pc).[5] No giant stars have been discovered in this cluster.[2] 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]

References
  1. Finlay, Warren H. (2014). Concise Catalog of Deep-Sky Objects (Second ed.). Springer. p. 155. doi:10.1007/978-3-319-03170-5. ISBN 978-3-319-03169-9.
  2. Ann, H. B.; et al. (February 2002). "BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters". The Astronomical Journal. 123 (2): 905–914. arXiv:astro-ph/0203028. Bibcode:2002AJ....123..905A. doi:10.1086/338309.
  3. Maurya, Jayanand; Joshi, Yogesh Chandra (October 2018). "Photometric study of the open cluster NGC 381". Bulletin de la Société Royale des Sciences de Liège. 88: 291–294. doi:10.25518/0037-9565.9003.
  4. Joshi, Y. C.; et al. (October 2016). "Study of open clusters within 1.8 kpc and understanding the Galactic structure". Astronomy & Astrophysics. 593: 13. arXiv:1606.06425. Bibcode:2016A&A...593A.116J. doi:10.1051/0004-6361/201628944. A116.
  5. Piskunov, A. E.; et al. (January 2008). "Tidal radii and masses of open clusters". Astronomy and Astrophysics. 477 (1): 165–172. Bibcode:2008A&A...477..165P. doi:10.1051/0004-6361:20078525.
  6. "NGC 381". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 22 December 2006.
  7. Hoskin, Michael (August 2006). "Caroline Herschel's catalogue of nebulae". Journal for the History of Astronomy. 37: 251–255. Bibcode:2006JHA....37..251H. doi:10.1177/002182860603700301.
  8. Hu, J. -H.; Ip, W. -H. (August 2007). Search for Exoplanets and Variables in the Open Cluster NGC 381. Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, International Astronomical Union. Symposium no. 240, held 22-25 August, 2006 in Prague, Czech Republic, S240. p. 333. Bibcode:2007IAUS..240..333H.
  9. Crinklaw, Greg; Etzel, Paul B. (October 1989). "A Photometric Analysis of the Eclipsing Binary OX Cassiopeiae". Astronomical Journal. 98: 1418. Bibcode:1989AJ.....98.1418C. doi:10.1086/115228.

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