2 Centauri

2 Centauri is a single[11] star in the southern constellation of Centaurus, located approximately 183 light years from Earth.[1] It has the Bayer designation g Centauri;[10] 2 Centauri is the Flamsteed designation. This object is visible to the naked eye as faint, red-hued star with an apparent visual magnitude of 4.19.[2] It is moving away from the Earth with a heliocentric radial velocity of +41 km/s.[6] The star is a member of the HD 1614 supercluster.[12]

This article is about g Centauri. It is not to be confused with G Centauri.
2 Centauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 49m 26.72175s[1]
Declination −34° 27′ 02.7929″[1]
Apparent magnitude (V) 4.19[2] (4.16 – 4.26)[3]
Characteristics
Spectral type M5 III[4]
U−B color index +1.44[5]
B−V color index +1.49[5]
Variable type SRb[3]
Astrometry
Radial velocity (Rv)+40.7±0.7[6] km/s
Proper motion (μ) RA: −41.68±0.23[1] mas/yr
Dec.: −59.77±0.18[1] mas/yr
Parallax (π)17.82 ± 0.21[1] mas
Distance183 ± 2 ly
(56.1 ± 0.7 pc)
Absolute magnitude (MV)+0.51[7]
Details
Radius70[8] R☉
Luminosity71.96[2] L☉
Temperature3,398[9] K
Other designations
g Centauri, 2 Cen, V806 Cen, CD−33° 9358, GC 18666, HD 120323, HIP 67457, HR 5192, SAO 204875[10]
Database references
SIMBADdata

This is an evolved red giant star with a stellar classification of M5 III.[4] It is classified as a semiregular variable star and its brightness varies from magnitude +4.16 to +4.26[3] with a period of 12.57 days.[13] The star has around 70[8] times the Sun's radius and is radiating 72[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,398 K.[9]

References
  1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  7. Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440, S2CID 12136256.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)". Astronomy and Astrophysics (Third ed.). 367: 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451. S2CID 425754.
  9. McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–357, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352
  10. "2 Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-06.
  11. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  12. Eggen, Olin J. (June 1998). "The HR 1614 Group and HIPPARCOS Astrometry". The Astronomical Journal. 115 (6): 2453–2458. Bibcode:1998AJ....115.2453E. doi:10.1086/300380.
  13. Ruban, E. V.; Arkharov, A. A.; Hagen-Thorn, E. I.; Novikov, V. V. (September 2009). "Physical parameters of the semiregular variable red giant 2 Cen". Astrophysics. 52 (3): 383–394. Bibcode:2009Ap.....52..383R. doi:10.1007/s10511-009-9075-3. S2CID 121256121.
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