Epsilon1 Arae

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Epsilon1 Arae
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
Cercle rouge 100%.svg
The location of ε1 Arae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ara
Right ascension 16h 59m 35.04880s[1]
Declination –53° 09′ 37.5713″[1]
Apparent magnitude (V) +4.068[2]
Spectral type K3 III[3]
U−B color index +1.71[4]
B−V color index +1.45[4]
Radial velocity (Rv) +23.1[5] km/s
Proper motion (μ) RA: +2.16[1] mas/yr
Dec.: +22.04[1] mas/yr
Parallax (π) 9.04 ± 0.27[1] mas
Distance 360 ± 10 ly
(111 ± 3 pc)
Absolute magnitude (MV) –0.79 ± 0.16[6]
Mass 1.74 ± 0.24[7] M
Radius 33.7 ± 3.4[7] R
Surface gravity (log g) 1.80[2] cgs
Temperature 4,176[2] K
Metallicity [Fe/H] 0.08 ± 0.05[2] dex
Age 1.70 ± 0.57[7] Gyr
Other designations
CPD–52° 10372, FK5 632, HD 152980, HIP 83153, HR 6295, SAO 244331.[8]
Database references

Epsilon1 Arae1 Ara, ε1 Arae) is the Bayer designation for a star in the constellation Ara, the Altar. It is visible to the naked eye with an apparent visual magnitude of +4.1[2] Based upon an annual parallax shift of 9.04 mas,[1] this star is around 360 light-years (110 parsecs) distant from the Earth.

ε1 Arae is an evolved giant star[7] with a stellar classification of K3 III.[3] It is around 74% more massive than the Sun. At an age of about 1.7 billion years, the outer envelope of the star has expanded to almost 34 times the Sun's radius.[7] It is radiating energy into space at an effective temperature of 4,176 K,[2] giving it the orange-hued glow of a K-type star.[9]

ε1 Arae was known as 龜一 (meaning: "the 1st (star) of Guī") in traditional Chinese astronomy.[10][11] Allen erroneously called it as Tso Kang (左更).[12] He probably confused constellation "Ara" with "Ari". Tso Kang was lain[clarification needed] in Aries.[10][11]


  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:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f Soubiran, C.; Le Campion, J.-F.; Cayrel de Strobel, G.; Caillo, A. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069Freely accessible, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247. 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H. 
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  5. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W. 
  6. ^ Setiawan, J.; et al. (July 2004), "Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch", Astronomy and Astrophysics, 421: 241–254, Bibcode:2004A&A...421..241S, doi:10.1051/0004-6361:20041042-1. 
  7. ^ a b c d e da Silva, L.; et al. (November 2006), "Basic physical parameters of a selected sample of evolved stars", Astronomy and Astrophysics, 458 (2): 609–623, arXiv:astro-ph/0608160Freely accessible, Bibcode:2006A&A...458..609D, doi:10.1051/0004-6361:20065105. 
  8. ^ "eps01 Ara". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-28. 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-07-21. 
  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.(in 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. 

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, 326.(in Japanese)

External links[edit]