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Alpha Centauri

This article is about α Centauri, the multi-star system in the constellation Centaurus and is not to be confused with a Centauri, A Centauri, or Centaurus A. For other uses, see Alpha Centauri (disambiguation).

Alpha Centauri AB[a]
Two bright stars against a dense background of fainter stars, with one of the fainter stars circled in red
Alpha Centauri AB (left) forms a triple star system with Proxima Centauri (below, south of, α Centauri AB), circled in red. The bright star to the right is Beta Centauri.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
α Centauri A (Rigil Kentaurus)
Right ascension 14h 39m 36.49400s[1]
Declination −60° 50′ 02.3737″[1]
Apparent magnitude (V) +0.01[2]
α Centauri B (Toliman)
Right ascension 14h 39m 35.06311s[1]
Declination −60° 50′ 15.0992″[1]
Apparent magnitude (V) +1.33[2]
Characteristics
A
Spectral type G2V[3]
B−V colour index +0.71[2]
B
Spectral type K1V[3]
B−V colour index +0.88[2]
Astrometry
A
Radial velocity (Rv)−21.4±0.76[4] km/s
Proper motion (μ) RA: −3679.25[1] mas/yr
Dec.: +473.67[1] mas/yr
Parallax (π)750.81±0.38 mas[5]
Distance4.344 ± 0.002 ly
(1.3319 ± 0.0007 pc)
Absolute magnitude (MV)4.38[6]
B
Radial velocity (Rv)−18.6±1.64[4] km/s
Proper motion (μ) RA: −3614.39[1] mas/yr
Dec.: +802.98[1] mas/yr
Parallax (π)750.81 ± 0.38 mas[5]
Distance4.344 ± 0.002 ly
(1.3319 ± 0.0007 pc)
Absolute magnitude (MV)5.71[6]
Orbit[5]
PrimaryA
CompanionB
Period (P)79.762±0.019 yr
Semi-major axis (a)17.493±0.0096″
Eccentricity (e)0.51947±0.00015
Inclination (i)79.243±0.0089°
Longitude of the node (Ω)205.073±0.025°
Periastron epoch (T)1875.66±0.012
Argument of periastron (ω)
(secondary)		231.519±0.027°
Details
α Centauri A
Mass1.0788±0.0029[5] M☉
Radius1.2175±0.0055[5] R☉
Luminosity1.5059±0.0019[5] L☉
Surface gravity (log g)4.30[7] cgs
Temperature5,804±13[8] K
Metallicity [Fe/H]0.20±0.01[8] dex
Rotation28.3±0.5 d[9]
Rotational velocity (v sin i)2.7±0.7[10] km/s
Age>4.8 Gyr
α Centauri B
Mass0.9092±0.0025[5] M☉
Radius0.8591±0.0036[5] R☉
Luminosity0.4981±0.0007[5] L☉
Surface gravity (log g)4.37[7] cgs
Temperature5,207±12[8] K
Metallicity [Fe/H]0.24±0.01[8] dex
Rotation36.7±0.3 d[11]
Rotational velocity (v sin i)1.1±0.8[12] km/s
Age5.3±0.3[13] Gyr
Other designations
Gliese 559, FK5 538, CD−60°5483, CCDM J14396-6050, GC 19728
α Cen A: Rigil Kentaurus, Rigil Kent, α1 Centauri, HR 5459, HD 128620, GCTP 3309.00, LHS 50, SAO 252838, HIP 71683
α Cen B: Toliman, α2 Centauri, HR 5460, HD 128621, LHS 51, HIP 71681
Database references
SIMBADAB
A
B
Exoplanet Archivedata
ARICNSdata

Alpha Centauri (α Centauri, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus (α Centauri A), Toliman (α Centauri B), and Proxima Centauri (α Centauri C).[14] Proxima Centauri is the closest star to the Sun at 4.2465 light-years (ly) which is 1.3020 pc.

Rigil Kentaurus and Toliman are Sun-like stars (class G and K, respectively) that together form the binary star system α Centauri AB. To the naked eye, these two main components appear to be a single star with an apparent magnitude of −0.27. It is the brightest star in the constellation and the third-brightest in the night sky, outshone by only Sirius and Canopus.

Rigil Kentaurus has 1.1 times the mass (M☉) and 1.5 times the luminosity of the Sun (L☉), while Toliman is smaller and cooler, at 0.9 M☉ and less than 0.5 L☉.[15] The pair orbit around a common centre with an orbital period of 79 years.[16] Their elliptical orbit is eccentric, so that the distance between A and B varies from 35.6 astronomical units (AU), or about the distance between Pluto and the Sun, to 11.2 AU, or about the distance between Saturn and the Sun. One astronomical unit is the distance from Earth to the Sun, 150 million kilometers.

Proxima Centauri is a small faint red dwarf (class M). Though not visible to the naked eye, Proxima Centauri is the closest star to the Sun at a distance of 4.24 ly (1.30 pc), slightly closer than α Centauri AB. The distance between Proxima Centauri and α Centauri AB is about 13,000 AU (0.21 ly),[17] equivalent to about 430 times the radius of Neptune's orbit.

Proxima Centauri has one confirmed planet: Proxima b, an Earth-sized planet in the habitable zone (though it is unlikely to be habitable), one candidate planet, Proxima d, sub-Earth which orbits very closely to the star,[18] and the controversial Proxima c, a mini-Neptune 1.5 astronomical units away.[19] Rigil Kentaurus may have a Neptune-sized planet in the habitable zone, though it is not yet known with certainty to be planetary in nature and could be an artifact of the discovery mechanism.[20] Toliman has no known planets.[21]


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

  1. ^ a b c d e f g h 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.
  2. ^ a b c d Ducati, J. R. (2002). Catalogue of Stellar Photometry in Johnson's 11 color system. VizieR Online Data Catalog (Report). CDS/ADC Collection of Electronic Catalogues. Vol. 2237. Bibcode:2002yCat.2237....0D.
  3. ^ a b Torres, C.A.O.; Quast, G.R.; da Silva, L.; de la Reza, R.; Melo, C.H.F.; Sterzik, M. (2006). "Search for associations containing young stars (SACY)". Astronomy and Astrophysics. 460 (3): 695–708. arXiv:astro-ph/0609258. Bibcode:2006A&A...460..695T. doi:10.1051/0004-6361:20065602. ISSN 0004-6361. S2CID 16080025.
  4. ^ a b Valenti, Jeff A.; Fischer, Debra A. (2005). "Spectroscopic properties of cool stars (SPOCS) I. 1040 F, G, and K dwarfs from Keck, Lick, and AAT planet search programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500. ISSN 0067-0049.
  5. ^ a b c d e f g h i Akeson, Rachel; Beichman, Charles; Kervella, Pierre; Fomalont, Edward; Benedict, G. Fritz (20 April 2021). "Precision millimeter astrometry of the α Centauri AB system". The Astronomical Journal. 162 (1): 14. arXiv:2104.10086. Bibcode:2021AJ....162...14A. doi:10.3847/1538-3881/abfaff. S2CID 233307418.
  6. ^ a b Cite error: The named reference Wiegert was invoked but never defined (see the help page).
  7. ^ a b Gilli, G.; Israelian, G.; Ecuvillon, A.; Santos, N.C.; Mayor, M. (2006). "Abundances of refractory elements in the atmospheres of stars with extrasolar planets". Astronomy and Astrophysics. 449 (2): 723–736. arXiv:astro-ph/0512219. Bibcode:2006A&A...449..723G. doi:10.1051/0004-6361:20053850. S2CID 13039037. libcode 2005astro.ph.12219G.
  8. ^ a b c d Soubiran, C.; Creevey, O. L.; Lagarde, N.; Brouillet, N.; Jofré, P.; Casamiquela, L.; Heiter, U.; Aguilera-Gómez, C.; Vitali, S.; Worley, C.; de Brito Silva, D. (1 February 2024). "Gaia FGK benchmark stars: Fundamental Teff and log g of the third version". Astronomy and Astrophysics. 682: A145. arXiv:2310.11302. Bibcode:2024A&A...682A.145S. doi:10.1051/0004-6361/202347136. ISSN 0004-6361. Alpha Centauri's database entry at VizieR.
  9. ^ Huber, Daniel; Zwintz, Konstanze; et al. (the BRITE team) (July 2020). "Solar-like oscillations: Lessons learned & first results from TESS". Stars and Their Variability Observed from Space: 457. arXiv:2007.02170. Bibcode:2020svos.conf..457H.
  10. ^ Bazot, M.; et al. (2007). "Asteroseismology of α Centauri A. Evidence of rotational splitting". Astronomy and Astrophysics. 470 (1): 295–302. arXiv:0706.1682. Bibcode:2007A&A...470..295B. doi:10.1051/0004-6361:20065694. S2CID 118785894.
  11. ^ Dumusque, Xavier (December 2014). "Deriving Stellar Inclination of Slow Rotators Using Stellar Activity". The Astrophysical Journal. 796 (2): 133. arXiv:1409.3593. Bibcode:2014ApJ...796..133D. doi:10.1088/0004-637X/796/2/133. S2CID 119184190.
  12. ^ Raassen, A.J.J.; Ness, J.-U.; Mewe, R.; van der Meer, R.L.J.; Burwitz, V.; Kaastran, J.S. (2003). "Chandra-LETGS X-ray observation of α Centauri: A nearby (G2V + K1V) binary system". Astronomy & Astrophysics. 400 (2): 671–678. Bibcode:2003A&A...400..671R. doi:10.1051/0004-6361:20021899.
  13. ^ Joyce, M.; Chaboyer, B. (2018). "Classically and asteroseismically constrained 1D stellar evolution models of α Centauri A and B using empirical mixing length calibrations". The Astrophysical Journal. 864 (1): 99. arXiv:1806.07567. Bibcode:2018ApJ...864...99J. doi:10.3847/1538-4357/aad464. S2CID 119482849.
  14. ^ Cite error: The named reference WGSN was invoked but never defined (see the help page).
  15. ^ Kervella, Pierre; Thevenin, Frederic (15 March 2003). "A family portrait of the Alpha Centauri system" (Press release). European Southern Observatory. p. 5. Bibcode:2003eso..pres...39. eso0307, PR 05/03.
  16. ^ Cite error: The named reference SixthCatOrbVisBin was invoked but never defined (see the help page).
  17. ^ Kervella, P.; Thévenin, F.; Lovis, C. (January 2017). "Proxima's orbit around α Centauri". Astronomy & Astrophysics. 598: L7. arXiv:1611.03495. Bibcode:2017A&A...598L...7K. doi:10.1051/0004-6361/201629930. S2CID 50867264.
  18. ^ Cite error: The named reference Faria2022 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Artigau2022 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference WagnerBoehle2021 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Rajpaul2016 was invoked but never defined (see the help page).

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