Location of ζ Centauri (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13 55 32.38565 |
| Declination | −47° 17′ 18.1482″ |
| Apparent magnitude (V) | +2.55 |
| Characteristics | |
| Spectral type | B2.5 IV |
| U−B color index | −0.91 |
| B−V color index | −0.22 |
| Astrometry | |
| Radial velocity (Rv) | +6.5 km/s |
| Proper motion (μ) | RA: −57.37 mas/yr Dec.: −44.55 mas/yr |
| Parallax (π) | 8.54 ± 0.13 mas |
| Distance | 382 ± 6 ly (117 ± 2 pc) |
| Absolute magnitude (MV) | −2.79 |
| Orbit | |
| Period (P) | 8.024 days |
| Semi-major axis (a) | 0.0014" |
| Eccentricity (e) | 0.5 |
| Periastron epoch (T) | 2413719.321 JD |
| Argument of periastron (ω) (secondary) | 290° |
| Details | |
| Mass | 7.8±0.1 M☉ |
| Radius | 5.80±0.53 R☉ |
| Surface gravity (log g) | 3.84±0.08 cgs |
| Temperature | 23561±283 K |
| Rotational velocity (v sin i) | 235 km/s |
| Age | 39.8±5.7 Myr |
| Other designations | |
| Alnair, ζ Cen, CD−46 8949, CPD−46 6560, HD 121263, HIP 68002, HR 5231, SAO 224538 | |
| Database references | |
| SIMBAD | data |
Zeta Centauri, Latinized from ζ Centauri, is a binary star system in the southern constellation of Centaurus. It has the proper name Alnair /æˈnɛər/, from Arabic: نير بطن قنطورس, romanized: nayyir baṭan qanṭūris, lit. 'the bright (star) of the body of the centaur'. With a combined apparent visual magnitude of +2.55, 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. It is drifting further away with a radial velocity of +6.5 km/s.
In Chinese, 庫樓 (Kù Lóu), meaning Arsenal, refers to an asterism consisting of ζ Centauri, η Centauri, θ Centauri, 2 Centauri, HD 117440, ξ Centauri, γ Centauri, τ Centauri, D Centauri and σ Centauri. Consequently, the Chinese name for ζ Centauri itself is 庫樓一 (Kù Lóu yī, English: the First Star of Arsenal.)
ζ Cen is a double-lined spectroscopic binary system, 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. The estimated angular separation of the pair is 1.4 mas.
At an estimated age of 40 million years, the primary component of this system appears to be in the subgiant stage of its evolution with a stellar classification of B2.5 IV. It is a large star with nearly 8 times the mass of the Sun and close to 6 times the Sun's radius. This star is rotating rapidly with a projected rotational velocity of 235 km s.
References
- ^ 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, S2CID 18759600
- ^ Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
- ^ 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, S2CID 118629873
- ^ Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W
- 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.
- ^ Maury, A. C. (1922), "The Orbit of the Spectroscopic Binary ζ Centauri", Harvard College Observatory Circular, 233: 1–4, Bibcode:1922HarCi.233....1M
- ^ Halbwachs, J. L. (April 1981), "List of Estimated Angular Separations of Spectroscopic Binaries", Astronomy and Astrophysics Supplement, 44: 47, Bibcode:1981A&AS...44...47H
- ^ 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, S2CID 119512018
- ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B
- "* zet Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-01.
- 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
- ibid., p.28.
- (in 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.
- (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日 Archived 2011-05-22 at the Wayback Machine
- 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
