Eta Aquarii

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η Aquarii
Aquarius constellation map.svg
Red circle.svg
Location of η Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  22h 35m 21.38126s[1]
Declination –00° 07′ 02.9888″[1]
Apparent magnitude (V) 4.04[2]
Characteristics
Spectral type B9IV-Vn[3]
U−B color index –0.28[4]
B−V color index –0.10[4]
Astrometry
Radial velocity (Rv)–8.0[2] km/s
Proper motion (μ) RA: +89.74[1] mas/yr
Dec.: –56.10[1] mas/yr
Parallax (π)19.43 ± 0.25[1] mas
Distance168 ± 2 ly
(51.5 ± 0.7 pc)
Absolute magnitude (MV)+0.48[5]
Details
Radius2.9[6] R
Luminosity91[5] L
Temperature11,219 ± 82[6] K
Rotational velocity (v sin i)291[7] km/s
Other designations
η Aqr, 62 Aquarii, BD-00 4384, FK5 850, HD 213998, HIP 111497, HR 8597, SAO 146181.[8]
Database references
SIMBADdata

Eta Aquarii, Latinized from η Aquarii, is the Bayer designation for a star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.04.[2] The distance to this star, as determined by parallax measurements, is about 168 light-years (52 parsecs).[1] Eta Aquarii is near the radiant of a meteor shower named after it.

Eta Aquarii has a stellar classification of B9IV-Vn,[3] which may indicate that it is beginning to evolve away from the main sequence into a subgiant as the supply of hydrogen at its core becomes exhausted, it is spinning rapidly with a high projected rotational velocity of 291 km/s.[7] This is causing an equatorial bulge, giving the star an oblate figure with a 24% larger radius at the equator than at the poles;[9] the Doppler effect from the rapid rotation is causing the absorption lines in the star's spectrum to blur, as indicated by the 'n' suffix in the star's classification.

Naming[edit]

This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and ζ Aqr (Sadaltager / Achr al Achbiya), were al Aḣbiyah (الأخبية), the Tent.[10][11]

In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of η Aquarii, γ Aquarii, ζ Aquarii, π Aquarii.[12] Consequently, the Chinese name for η Aquarii itself is 墳墓三 (Fén Mù sān, English: the Third Star of Tomb.)[13]

References[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:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b c Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, Astronomisches Rechen-Institut Heidelberg, 35 (35), Bibcode:1999VeARI..35....1W.
  3. ^ a b Cowley, A. (November 1972), "Spectral classification of the bright B8 stars", Astronomical Journal, 77: 750–755, Bibcode:1972AJ.....77..750C, doi:10.1086/111348.
  4. ^ a b 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.
  5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. ^ a b Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601.
  7. ^ a b Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  8. ^ "eta Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-30.
  9. ^ van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.
  10. ^ Davis, George R (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 8. Bibcode:1944PA.....52....8D.
  11. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 52. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  12. ^ ‹See Tfd›(in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ^ ‹See Tfd›(in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日

External links[edit]