Zeta Centauri

Zeta Centauri
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings


Location of ζ Centauri (circled)

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 55m 32.38565s[1]
Declination −47° 17′ 18.1482″[1]
Apparent magnitude (V) +2.55[2]
Characteristics
Spectral type B2.5 IV[3]
U−B color index −0.91[2]
B−V color index −0.22[2]
Astrometry
Radial velocity (Rv)+6.5[4] km/s
Proper motion (μ) RA: −57.37[1] mas/yr
Dec.: −44.55[1] mas/yr
Parallax (π)8.54 ± 0.13[1] mas
Distance382 ± 6 ly
(117 ± 2 pc)
Orbit[5]
Period (P)8.024 days
Semi-major axis (a)0.0014"[6]
Eccentricity (e)0.5
Periastron epoch (T)2413719.321 JD
Argument of periastron (ω)
(secondary)		290°
Details
Mass7.8 ± 0.1[3] M☉
Radius5.80 ± 0.53[7] R☉
Surface gravity (log g)3.84 ± 0.08[7] cgs
Temperature23,561 ± 283[7] K
Rotational velocity (v sin i)235[8] km/s
Age39.8 ± 5.7[3] Myr
Other designations
Alnair, CD−46 8949, CP−46 6560, HD 121263, HIP 68002, HR 5231, SAO 224538.[9]
Database references
SIMBADdata

Zeta Centauri (ζ Centauri, ζ Cen) is a binary star system in the southern constellation of Centaurus. It has the proper name Alnair, from the scientific-Arabic[10] Nayyir Badan Qanṭūris (ألناير ألبطن ألقنتورس), meaning "The Bright (Star) of the Body of the Centaur".[11] With a combined apparent visual magnitude of +2.55,[2] it is one of the brighter members of the constellation. This system is close enough to the Earth that its distance can be measured directly using the parallax technique. This yields a value of roughly 382 light-years (117 parsecs), with a 1.6% margin of error.[1]

In Chinese, 庫樓 (Kù Lóu), meaning Arsenal, refers to an asterism consisting of ζ Centauri, η Centauri, θ Centauri, 2 Centauri, HD 117440, ξ1 Centauri, γ Centauri, τ Centauri, D Centauri and σ Centauri.[12] Consequently, ζ Centauri itself is known as 庫樓一 (Kù Lóu yī, English: the First Star of Arsenal.)[13]

ζ Cen is a double-lined spectroscopic binary system,[14] which indicates that the orbital motion was detected by shifts in the absorption lines of their combined spectra caused by the Doppler effect. The two stars orbit each other over a period of slightly more than eight days with an orbital eccentricity of about 0.5.[5] The estimated angular separation of the pair is 1.4 mas.[6]

At an estimated age of 40 million years,[3] the primary component of this system appears to be in the subgiant stage of its evolution with a stellar classification of B2.5 IV.[3] It is a large star with nearly 8[3] times the mass of the Sun and close to 6[7] times the Sun's radius. This star is rotating rapidly with a projected rotational velocity of 235 km s−1.[8]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 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
  2. ↑ 2.0 2.1 2.2 2.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
  4. ↑ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W
  5. ↑ 5.0 5.1 Maury, A. C. (1922), "The Orbit of the Spectroscopic Binary ζ Centauri", Harvard College Observatory Circular 233: 1–4, Bibcode:1922HarCi.233....1M
  6. ↑ 6.0 6.1 Halbwachs, J. L. (April 1981), "List of Estimated Angular Separations of Spectroscopic Binaries", Astronomy and Astrophysics Supplement 44: 47, Bibcode:1981A&AS...44...47H
  7. ↑ 7.0 7.1 7.2 7.3 Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal 129 (3): 1642–1662, arXiv:astro-ph/0412542, Bibcode:2005AJ....129.1642F, doi:10.1086/427855
  8. ↑ 8.0 8.1 Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago 239 (1), Bibcode:1970CoAsi.239....1B
  9. ↑ "zet Cen -- Spectroscopic binary", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-03-01
  10. ↑ Kunitzsch, P.; Smart, T. (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd revised ed.), Cambridge, MA: Sky Pub, p. 4, ISBN 978-1-931559-44-7
  11. ↑ ibid., p.28.
  12. ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日
  14. ↑ van Rensbergen, W.; De Loore, C.; Jansen, K. (February 2006), "Evolution of interacting binaries with a B type primary at birth", Astronomy and Astrophysics 446 (3): 1071–1079, Bibcode:2006A&A...446.1071V, doi:10.1051/0004-6361:20053543