Eta Aquarii

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Eta Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.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
Distance 168 ± 2 ly
(51.5 ± 0.7 pc)
Details
Radius 2.9[5] R
Temperature 11,219 ± 82[5] K
Rotational velocity (v sin i) 291[6] km/s
Other designations
62 Aquarii, BD-00 4384, FK5 850, HD 213998, HIP 111497, HR 8597, SAO 146181.[7]

Eta Aquarii (η Aqr, 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.[6] This is causing an equatorial bulge, giving the star an oblate figure with a 24% larger radius at the equator than at the poles.[8] 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.

Etymology[edit]

This star sometimes called with the name Hydria, from the Greek word ‘υδρια (hudria), meaning "water jar".[9] Another name of this star is Deli, derived from Hebrew word דלי (dali) literally meaning "hard".[10][unreliable source?]

This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and ζ Aqr (Sadaltager / Achr al Achbiya), were al Aḣbiyah (الأخبية), the Tent.[11][12][13]

In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of η Aquarii, γ Aquarii, ζ Aquarii, π Aquarii.[14] Consequently, η Aquarii itself is known as 墳墓三 (Fén Mù sān, English: the Third Star of Tomb.)[15]

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 (35), Astronomisches Rechen-Institut Heidelberg, 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), Bibcode:1966CoLPL...4...99J. 
  5. ^ 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: 601–605, Bibcode:1979MNRAS.189..601U. 
  6. ^ 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. 
  7. ^ "eta Aqr -- Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-06-30. 
  8. ^ 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. 
  9. ^ (Turkish) YILDIZ ADLARI SÖZLÜĞÜ - Mustafa Pultar (Hydria)
  10. ^ (Turkish) YILDIZ ADLARI SÖZLÜĞÜ - Mustafa Pultar (Deli)
  11. ^ Davis Jr., G. A., "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names,"Popular Astronomy, Vol. LII, No. 3, Oct. 1944, p. 12.
  12. ^ 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. 
  13. ^ γ Aqr as Aoul al Achbiya or Prima Tabernaculorum (the first of luck of the homes or tents), π Aqr as Wasat al Achbiya or Media Tabernaculorum (the middle of luck of the homes or tents) and ζ Aqr as Achr al Achbiya or Postrema Tabernaculorum (the end of luck of the homes or tents). η Aqr should be designated as al Achbiya consistently, but it was not designated as the Arabian name except the name Hydria (Greek) or Deli (Hebrew)
  14. ^ (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.
  15. ^ (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]