Eta Columbae

Eta Columbae is a solitary[8] star near the southern boundary of the constellation Columba.[9] It is visible to the naked eye, having an apparent visual magnitude of 3.96.[2] Based upon an annual parallax shift of 6.91 mas,[1] it lies at a distance of roughly 472 light years from the Sun.

η Columbae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Columba
Right ascension 05h 59m 08.80519s[1]
Declination −42° 48′ 54.4822″[1]
Apparent magnitude (V) 3.96[2]
Characteristics
Spectral type G8/K1 II[3] or K0 III[4]
U−B color index +1.08[2]
B−V color index +1.14[2]
Astrometry
Radial velocity (Rv)+17.0[4] km/s
Proper motion (μ) RA: +18.39[1] mas/yr
Dec.: −10.87[1] mas/yr
Parallax (π)6.91 ± 0.12[1] mas
Distance472 ± 8 ly
(145 ± 3 pc)
Absolute magnitude (MV)−2.10[5]
Details[4]
Mass3.33 M☉
Radius38.6[6] R☉
Luminosity708 L☉
Surface gravity (log g)1.72 cgs
Temperature4,620±54 K
Metallicity [Fe/H]−0.01 dex
Other designations
η Col, CD−42° 2266, FK5 229, HD 40808, HIP 28328, HR 2120, SAO 217650.[7]
Database references
SIMBADdata

This is an orange-hued[9] K-type giant star with a stellar classification of K0 III,[4] or possibly a bright giant with a crossover class of G8/K1 II.[3] The measured angular diameter of this star, after correction for limb darkening, is 2.48±0.03 mas.[10] At the estimated distance of this star, this yields a physical size of about 38.6 times the radius of the Sun.[6] It has an estimated 3.33 times the mass of the Sun and radiates 708 times the solar luminosity from its outer atmosphere at an effective temperature of 4,620 K.[4]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. 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.
  3. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88.
  5. Böhm-Vitense, Erika; et al. (December 2000), "Ultraviolet Emission Lines in BA and Non-BA Giants", The Astrophysical Journal, 545 (2): 992–999, Bibcode:2000ApJ...545..992B, doi:10.1086/317850.
  6. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  7. "eta Col -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-12-23.
  8. 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.
  9. Kambic, Bojan (2009), Viewing the Constellations with Binoculars: 250+ Wonderful Sky Objects to See and Explore, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 260, ISBN 0387853553.
  10. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
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