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Alpha Centauri

For other uses, see Alpha Centauri (disambiguation). "α Centauri" redirects here. Not to be confused with a Centauri, A Centauri or Centaurus A. "Toliman" redirects here. For other uses, see Toliman (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, circled in red. The bright star system to the right is Beta Centauri.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
α Centauri A
Right ascension 14h 39m 36.49400s[1]
Declination −60° 50′ 02.3737″
Apparent magnitude (V) +0.01[2]
α Centauri B
Right ascension 14h 39m 35.06311s[1]
Declination −60° 50′ 15.0992″
Apparent magnitude (V) +1.33[2]
Characteristics
A
Spectral type G2V[3]
U−B color index +0.24[citation needed]
B−V color index +0.71[2]
B
Spectral type K1V[3]
U−B color index +0.68[citation needed]
B−V color 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
Temperature5,891[8] K
Metallicity [Fe/H]0.21[8] dex
Rotation28.3±0.5 d[9]
Rotational velocity (v sin i)2.7±0.7[10] km/s
Age4.85 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
Temperature5,151[8] K
Metallicity [Fe/H]0.12[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
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 triple 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 (1.3020 pc).

α Centauri A and B 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.

α Centauri A has 1.1 times the mass and 1.5 times the luminosity of the Sun, while α Centauri B is smaller and cooler, at 0.9 solar mass and less than 0.5 solar luminosity.[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.

α Centauri C, or 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. Currently, 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 two confirmed planets: Proxima b, an Earth-sized planet in the habitable zone discovered in 2016, and Proxima d, a candidate sub-Earth which orbits very closely to the star, announced in 2022.[18] The existence of Proxima c, a mini-Neptune 1.5 AU away discovered in 2019, is controversial.[19] α Centauri A 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] α Centauri B has no known planets: Planet α Cen Bb, purportedly discovered in 2012, was later disproven,[21] and no other planet has yet been confirmed.


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 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 Gomes da Silva, J.; Santos, N. C.; Adibekyan, V.; Sousa, S. G.; Campante, T. L.; Figueira, P.; Bossini, D.; Delgado-Mena, E.; Monteiro, M. J. P. F. G.; de Laverny, P.; Recio-Blanco, A.; Lovis, C. (1 February 2021). "Stellar chromospheric activity of 1674 FGK stars from the AMBRE-HARPS sample. I. A catalogue of homogeneous chromospheric activity". Astronomy and Astrophysics. 646: A77. arXiv:2012.10199. doi:10.1051/0004-6361/202039765. 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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