Astronomy:Zeta Arae

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Short description
Star in the constellation Ara.
ζ Arae
Ara constellation map.svg
Red circle.svg
Location of ζ Arae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ara
Right ascension  16h 58m 37.21217s[1]
Declination –55° 59′ 24.5203″[1]
Apparent magnitude (V) 3.13[2]
Spectral type K3 III[3]
U−B color index +1.96[2]
B−V color index +1.60[2]
Radial velocity (Rv)–6.0[4] km/s
Proper motion (μ) RA: –17.80[1] mas/yr
Dec.: –36.67[1] mas/yr
Parallax (π)6.71 ± 0.19[1] mas
Distance490 ± 10 ly
(149 ± 4 pc)
Absolute magnitude (MV)–3.95[5]
Mass7-8[6] M
Radius114[6] R
Luminosity3,800[6] L
Surface gravity (log g)1.20[6] cgs
Temperature4,246[6] K
Metallicity [Fe/H]–0.40[7] dex
Other designations
Tseen Yin, GJ 9581, SAO 244315, HD 152786, FK5 631, HIP 83081, HR 6285, CPD−55° 7766[8]
Database references

Zeta Arae (ζ Ara, ζ Arae) is the third-brightest star in the southern constellation Ara.[9] The apparent visual magnitude of this star is 3.1,[2] which can be seen from suburban skies in the southern hemisphere. From the parallax measurements, it is located at a distance of 490 light-years (150 parsecs) from Earth.[1]

The spectrum of this star matches a stellar classification of K3 III.[3] The luminosity class of 'III' indicates this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. It is radiating energy from its outer atmosphere at an effective temperature of 4,246 K which is what gives it the orange hue of a K-type star.[10] This star displays an excess of infrared emission that may indicate circumstellar matter.[11]

In Chinese, (Guī), meaning Tortoise, refers to an asterism consisting of ζ Arae, ε1 Arae, γ Arae, δ Arae and η Arae.[12] Consequently, the Chinese name for ζ Arae itself is 龜五 (Guī wǔ, English: the Fifth Star of Tortoise.)[13]

Allen called it Tseen Yin /ˌsnˈjɪn/, together with δ Arae, from the Chinese 天陰 (Mandarin pronunciation tiānyīn) "dark sky".[14] However, 天陰 is in Aries.[15][16] so Allen probably confused constellation "Ara" with "Ari".


  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, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V 
  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): 99, Bibcode1966CoLPL...4...99J 
  3. 3.0 3.1 Houk, Nancy (1978), "Michigan catalogue of two-dimensional spectral types for the HD stars", University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0 (Ann Arbor: Dept. of Astronomy, University of Michigan) 1, 
  4. Wielen, R. et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb (Astronomisches Rechen-Institut Heidelberg) 35 (35): 1, Bibcode1999VeARI..35....1W 
  5. Jasniewicz, G. et al. (February 1999), "Late-type giants with infrared excess. I. Lithium abundances", Astronomy and Astrophysics 342: 831–838, Bibcode1999A&A...342..831J 
  6. 6.0 6.1 6.2 6.3 6.4 Cruzalèbes, P.; Jorissen, A.; Rabbia, Y.; Sacuto, S.; Chiavassa, A.; Pasquato, E.; Plez, B.; Eriksson, K. et al. (2013). "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER". Monthly Notices of the Royal Astronomical Society 434 (1): 437. doi:10.1093/mnras/stt1037. Bibcode2013MNRAS.434..437C. 
  7. Jones, K. L. et al. (June 1992), "Spectroscopic investigation of cool giants and the authenticity of their reported microwave emission", Monthly Notices of the Royal Astronomical Society 256 (3): 535–544, doi:10.1093/mnras/256.3.535, Bibcode1992MNRAS.256..535J 
  8. "zet Ara -- Star", SIMBAD (Centre de Données astronomiques de Strasbourg),, retrieved 2012-01-05 
  9. Kaler, Jim (13 July 2012). "Zeta Arae". University of Illinois. 
  10. "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004,, retrieved 2012-01-16 
  11. Plets, H. et al. (July 1997), "Giants with infrared excess", Astronomy and Astrophysics 323: 513–523, Bibcode1997A&A...323..513P 
  12. (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.
  13. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 1 日
  14. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc.. p. 64. ISBN 0-486-21079-0. 
  15. Chevalier, S., and Tsuchihashi, P., (1911): "Catalogue d'Étoiles fixes, observés a Pekin sous l'Empereur Kien Long (Qianlong (Chien-Lung)), XVIIIe siecle", Annales de l'Observatoire Astronomique de Zô-Sé.
  16. 伊世同 (Yi Shi Tong) (1981): 『中西対照恒星図表』科学出版社.(in Chinese)

External links