Delta Arae

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Delta Arae
Ara constellation map.png
δ Arae (lower center) in the Ara Constellation
Observation data
Epoch J2000.0      Equinox J2000.0
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
Distance 198 ± 4 ly
(61 ± 1 pc)
Mass 3.56[6] M
Radius 3.12 ± 0.15[7] R
Surface gravity (log g) 3.81 ± 0.06[7] cgs
Temperature 11,962 ± 86[7] K
Rotational velocity (v sin i) 255[4] km/s
Age 125[8] Myr
Other designations
CPD –60° 6842, FK5 648, HD 158094, HIP 85727, HR 6500, SAO 253945.[9]

Delta Arae (δ Arae, δ Ara) 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.[6]

There is a 12th magnitude optical companion located 47.4 arcseconds away along a position angle of 313°.[8]


Delta Arae was known as 龜三 (meaning: "the 3rd (star) of Guī") in traditional Chinese astronomy.[10][11]

Allen erroneously called it with ζ Arae as Tseen Yin (天陰).[12] He probably confused constellation "Ara" with "Ari". Tseen Yin was lain[clarification needed] in Aries.[10][11]

See also[edit]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N. 
  3. ^ a b 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. ^ a b c van Belle, Gerard T., Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572free to read, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2. 
  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, p. 57, Bibcode:1967IAUS...30...57E. 
  6. ^ a b 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, arXiv:1007.0425free to read, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2. 
  7. ^ a b c 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/0412542free to read, Bibcode:2005AJ....129.1642F, doi:10.1086/427855. 
  8. ^ a b Ehrenreich, D.; et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics, 523: A73, arXiv:1007.0002free to read, Bibcode:2010A&A...523A..73E, doi:10.1051/0004-6361/201014763. 
  9. ^ "del Ara -- Star in double system", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-27. 
  10. ^ a b 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.
  11. ^ a b 伊世同 (Yi Shi Tong) (1981): 『中西対照恒星図表』科学出版社.(Chinese)
  12. ^ 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. [1]

Further reading[edit]

  • 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.(Japanese)

External links[edit]