31 Comae Berenices

31 Comae Berenices (31 Com) is a yellow giant star in the constellation Coma Berenices. Its apparent magnitude is about 4.9 and slightly variable. It is a rare FK Comae Berenices variable, a variable star that spins rapidly and has large starspots on its surface.^[5] It is currently in the Hertzsprung gap and its outer envelope has just begun convection.^[3] In 1989 it was given as a spectral standard for the class G0IIIp.^[6]

31 Comae Berenices

Observation data Epoch J2000      Equinox J2000
Constellation	Coma Berenices
Right ascension	12h 51m 41.91900s[1]
Declination	+27° 32′ 26.5683″[1]
Apparent magnitude (V)	4.87 - 4.97[2]
Characteristics
Evolutionary stage	Hertzsprung gap[3]
Spectral type	G0III[4]
Variable type	FK Com[2]
Astrometry
Proper motion (μ)	RA: −10.990[1] mas/yr Dec.: −8.313[1] mas/yr
Parallax (π)	11.4933 ± 0.1828 mas[1]
Distance	284 ± 5 ly (87 ± 1 pc)
Details[4]
Radius	8.9 R☉
Luminosity	74 L☉
Surface gravity (log g)	3.51 cgs
Temperature	5,660 K
Metallicity [Fe/H]	−0.15 dex
Rotation	6.8 d
Rotational velocity (v sin i)	67 km/s
Other designations
31 Com, LS Comae Berenices, BD+28°2156, FK5 1332, HD 111812, HIP 62763, HR 4883, SAO 82537[5]
Database references
SIMBAD	data

31 Com is the north galactic pole star, and occasionally goes by the informal name Polaris Galacticum Borealis, coined by Jim Kaler.^[7]

In Chinese astronomy, 31 Comae Berenices is called 郎將, Pinyin: Lángjiāng, meaning Captain of the Bodyguards, because this star is marking itself and stand alone in Captain of the Bodyguards asterism, Supreme Palace enclosure mansion (see : Chinese constellation).^[8]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
2. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
3. Strassmeier, K. G.; et al. (September 2010), "Rotation and magnetic activity of the Hertzsprung-gap giant 31 Comae", Astronomy and Astrophysics, 520: 14, Bibcode:2010A&A...520A..52S, doi:10.1051/0004-6361/201015023, A52.
4. Aurière, M.; et al. (February 2015), "The magnetic fields at the surface of active single G-K giants", Astronomy & Astrophysics, 574: 30, arXiv:1411.6230, Bibcode:2015A&A...574A..90A, doi:10.1051/0004-6361/201424579, S2CID 118504829, A90.
5. "31 Com". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 13, 2018.
6. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins Catalog of Revised MK Types for the Cooler Stars", The Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
7. "Polaris Galacticum Borealis". Retrieved 2015-12-02.
8. Ian Ridpath's Startales - Coma Berenices the Berenice's Hair