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Eta Arae

Eta Arae is a single[7] star in the southern constellation of Ara. Its name is a Bayer designation that is Latinized from η Arae, and abbreviated Eta Ara or η Ara. This star is visible to the naked eye with an apparent visual magnitude of 3.76.[2] Based on parallax measurements, it is approximately 305 light-years (94 parsecs) distance from Earth.[1] The star is moving away from the Sun with a radial velocity of +9 km/s.[4]

The spectrum of this star matches a stellar classification of K5 III,[3] indicating that, at an estimated age of five billion years,[4] it has reached the giant star stage of its evolution. With 1.12 times the mass of the Sun, it has an outer envelope that has expanded to 40 times the Sun's radius.[4] The star is now spinning so slowly that it takes more than eleven years to complete a single rotation.[8] Eta Arae is radiating energy into space from its photosphere with 575 times the Sun's luminosity at an effective temperature of 4,147 K,[4] giving it the orange-hued glow of a K-type star.[9]

It has a magnitude 13.5 optical companion, located 23.4 arcseconds away along a position angle of 118°, as of 2000.[10]

References

  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b c d 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. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H.
  4. ^ a b c d e f Jofré, E.; et al. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574: A50, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, S2CID 53666931.
  5. ^ 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/0608160, Bibcode:2006A&A...458..609D, doi:10.1051/0004-6361:20065105, S2CID 9341088.
  6. ^ "eta Ara", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2024-01-28.
  7. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  8. ^ 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 (1): 241–254, Bibcode:2004A&A...421..241S, doi:10.1051/0004-6361:20041042-1.
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-06-24.
  10. ^ Mason, B. D.; Wycoff, G. L. I.; Hartkopf, W. I. (2008), Washington Visual Double Star Catalog, 2006.5 (WDS), U. S.Naval Observatory, Washington D.C., archived from the original on 2011-02-14, retrieved 2017-12-08.