Zeta Centauri

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Zeta Centauri
Centaurus IAU.svg
Red circle.svg
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  mas [1]
Distance 382 ± 6  ly
(117 ± 2  pc)
Absolute magnitude  (MV)−2.79 [5]
Orbit [6]
Period (P)8.024 days
Semi-major axis (a)0.0014" [7]
Eccentricity (e)0.5
Periastron epoch (T)2413719.321  JD
Argument of periastron (ω)
(secondary)		290°
Details
Mass 7.8±0.1 [3]   M☉
Radius 5.80±0.53 [8]   R☉
Luminosity 5,884 [5]   L☉
Surface gravity (log g)3.84±0.08 [8]   cgs
Temperature 23561±283 [8]   K
Rotational velocity (v sin i)235 [9]  km/s
Age 39.8±5.7 [3]   Myr
Other designations
Leepwal, ζ Cen, CD−46 8949, CPD−46 6560, HD 121263, HIP 68002, HR 5231, SAO 224538 [10]
Database references
SIMBAD data

Zeta Centauri is a binary star system in the southern constellation of Centaurus. It has the proper name Leepwal; [11] Zeta Centauri is its Bayer designation. 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] It is drifting further away with a radial velocity of +6.5 km/s. [4]

ζ Cen is a double-lined spectroscopic binary system, [12] 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. [6] The estimated angular separation of the pair is 1.4  mas. [7]

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 [8] times the Sun's radius. This star is rotating rapidly with a projected rotational velocity of 235 km s−1. [9]

Nomenclature

Zeta Centauri, Latinized from ζ Centauri, is the star's Bayer designation. Along with other modern Bayer designations in Centaurus, it was assigned by Nicolas Louis de Lacaille in his 1756 star catalog; the star referred to as ζ Centauri in Bayer's Uranometria of 1603 is Acrux in the Southern Cross, then considered part of Centaurus. [13]

This star has been referred to by the proper name Alnair /æˈnɛər/ , from Arabic : نير بطن قنطورس, romanized: nayyir baṭan qanṭūris, lit.  'the bright (star) of the body of the centaur ', [14] [15] though this was originally a name for Acrux (see above). [16] [13] Alnair is also the proper name of α Gruis and was officially approved by the IAU as the name of that star. [11] This star has also been referred to as Baten Kentaurus, from the same Arabic source. [17]

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. [18] Consequently, the Chinese name for ζ Centauri itself is 庫樓一 (Kù Lóu yī, English: the First Star of Arsenal.) [19] (See also ι Centauri.)

In Marshallese, this star is named Ļeepwal (pronounced leyepwal), the third of the ten sons of Lōktañūr (Capella). [20] The IAU Working Group on Star Names approved the name Leepwal for Zeta Centauri A on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names. [11]

References

  1. 1 2 3 4 5 6 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
  2. 1 2 3 4 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
  3. 1 2 3 4 5 6 Tetzlaff, N.; et al. (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
  4. 1 2 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
  5. 1 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. XHIP record for this object at VizieR.
  6. 1 2 Maury, A. C. (1922), "The Orbit of the Spectroscopic Binary ζ Centauri", Harvard College Observatory Circular, 233: 1–4, Bibcode:1922HarCi.233....1M
  7. 1 2 Halbwachs, J. L. (April 1981), "List of Estimated Angular Separations of Spectroscopic Binaries", Astronomy and Astrophysics Supplement, 44: 47, Bibcode:1981A&AS...44...47H
  8. 1 2 3 4 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
  9. 1 2 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
  10. ↑ "* zet Cen", SIMBAD , Centre de données astronomiques de Strasbourg , retrieved 2012-03-01.
  11. 1 2 3 IAU Catalog of Star Names , retrieved 22 February 2025.
  12. ↑ van Rensbergen, W.; et al. (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
  13. 1 2 Ridpath, Ian, Star Tales - Crux , retrieved 26 July 2025.
  14. ↑ 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
  15. ↑ ibid., p.28.
  16. ↑ Allen, R.H. (1899), Star Names: Their Lore and Meaning, p. 154
  17. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
  18. ↑ (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.
  19. ↑ (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
  20. ↑ "Leepwal", All Skies Encyclopaedia, IAU Working Group on Star Names , retrieved 12 May 2025.
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