Astronomy:Delta Arae

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Short description: Star in the constellation Ara
Delta Arae
Ara constellation map.png
δ Arae (lower center) in the Ara Constellation
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ara
Right ascension  17h 31m 05.91272s[1]
Declination –60° 41′ 01.8522″[1]
Apparent magnitude (V) 3.62[2]
Spectral type B8 Vn[3] + G8 V[4]
U−B color index –0.31[2]
B−V color index –0.10[2]
Radial velocity (Rv)+10[5] km/s
Proper motion (μ) RA: –54.01[1] mas/yr
Dec.: –99.25[1] mas/yr
Parallax (π)16.48 ± 0.34[1] mas
Distance198 ± 4 ly
(61 ± 1 pc)
Absolute magnitude (MV)−0.31[6]
Mass3.56[7] M
Radius3.12 ± 0.15[8] R
Luminosity214[6] L
Surface gravity (log g)3.81 ± 0.06[8] cgs
Temperature11,962 ± 86[8] K
Rotational velocity (v sin i)255[4] km/s
Age125[9] Myr
Other designations
δ Ara, CPD –60° 6842, FK5 648, HD 158094, HIP 85727, HR 6500, SAO 253945.[10]
Database references

Delta Arae, Latinized from δ Arae, is the Bayer designation for a double star in the southern constellation Ara. It has an apparent visual magnitude of 3.62[2] and is visible to the naked eye. Based upon an annual parallax of 16.48 mas, it is about 198 light-years (61 parsecs) distant from the Earth.[1]

Delta Arae is massive B-type main sequence star with a stellar classification of B8 Vn.[3] The 'n' suffix indicates the absorption lines are spread out broadly because the star is spinning rapidly. It has a projected rotational velocity of 255 km/s, resulting in an equatorial bulge with a radius 13% larger than the polar radius.[4] It has a magnitude 9.5 companion G-type main sequence star that may form a binary star system with Delta Arae.[7]

There is a 12th magnitude optical companion located 47.4 arcseconds away along a position angle of 313°.[9]


Delta Arae was known as 龜三 (meaning: "the 3rd (star) of Guī") in traditional Chinese astronomy.[11][12]

Allen erroneously called both Delta and Zeta Arae "Tseen Yin" (天陰).[13] He probably confused the constellation "Ara" with "Ari", as 天陰 is actually in Aries.[11][12]

See also

  • Ara (Chinese astronomy)
  • Aries (Chinese astronomy)


  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 Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series 34: 1–49, Bibcode1978A&AS...34....1N. 
  3. 3.0 3.1 Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Ann Arbor : Dept. Of Astronomy (Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan) 1, 
  4. 4.0 4.1 4.2 van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode2012A&ARv..20...51V. 
  5. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, 30, University of Toronto: International Astronomical Union, pp. 57, Bibcode1967IAUS...30...57E. 
  6. 6.0 6.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode2012AstL...38..331A. 
  7. 7.0 7.1 Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement 192 (1): 2, doi:10.1088/0067-0049/192/1/2, Bibcode2011ApJS..192....2S. 
  8. 8.0 8.1 8.2 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, doi:10.1086/427855, Bibcode2005AJ....129.1642F. 
  9. 9.0 9.1 Ehrenreich, D. et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics 523: A73, doi:10.1051/0004-6361/201014763, Bibcode2010A&A...523A..73E. 
  10. "del Ara". SIMBAD. Centre de données astronomiques de Strasbourg. 
  11. 11.0 11.1 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.
  12. 12.0 12.1 伊世同 (Yi Shi Tong) (1981): 『中西対照恒星図表』科学出版社.(in Chinese)
  13. 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. 

Further reading

  • 大崎正次 (1987): 「中国の星座・星名の同定一覧表」『中国の星座の歴史』 雄山閣出版, pp. 312, 328.(in Japanese)

External links