Zeta Aquilae

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ζ Aquilae
Aquila constellation map.svg
Red circle.svg
Location of ζ Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 05m 24.60802s[1]
Declination +13° 51′ 48.5182″[1]
Apparent magnitude (V) 2.983[2]
Spectral type A0 Vn[3]
U−B color index +0.080[2]
B−V color index +0.009[2]
Radial velocity (Rv) –25[4] km/s
Proper motion (μ) RA: -.25[1] mas/yr
Dec.: –95.56[1] mas/yr
Parallax (π) 39.28 ± 0.16[1] mas
Distance 83.0 ± 0.3 ly
(25.5 ± 0.1 pc)
Absolute magnitude (MV) +0.96[5]
Mass 2.37[6] M
Radius 2.27[7] R
Luminosity 39.4[7] L
Surface gravity (log g) 4.17[8] cgs
Temperature 9,620 ± 20[7] K
Metallicity [Fe/H] −0.52±0.04[5] dex
Rotational velocity (v sin i) 317[9] km/s
Age 100 ± 50[7] Myr
Other designations
Deneb el Okab, ζ Aql, 17 Aql, BD+13 3899, FK5 716, GJ 4095, HD 177724, HIP 93747, HR 7235, SAO 104461.[10]
Database references

Zeta Aquilae, Latinized from ζ Aquilae, is a double star in the equatorial constellation of Aquila. It has the traditional name Deneb el Okab, meaning "the tail of the eagle". As a third magnitude star,[2] Zeta Aquilae is readily visible with the naked eye. Parallax measurements place it at a distance of approximately 83 light-years (25 parsecs) from Earth.[1]


Zeta Aquilae has a stellar classification of A0 Vn,[3] with the luminosity class 'V' indicating is a main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. It has more than double the mass and twice the radius of the Sun,[6][7] and is radiating more than 39 times the Sun's luminosity.[7] The effective temperature of the star's outer envelope is about 9620 K,[7] which gives it the white hue typical of A-type stars. The estimated age of this star is 50–150 million years.[6]

This star is rotating rapidly, with a projected rotational velocity of 317 km s−1 giving a lower bound on the azimuthal velocity along the equator.[9] As a result, it has a pronounced equatorial bulge, causing the star to assume an oblate spheroidal shape. The equatorial radius is about 30.7% greater than the polar radius.[6] Because of the Doppler effect, this rapid rotation makes the absorption lines in the star's spectrum broaden and smear out, as indicated by the 'n' suffix in the stellar class.

Astronomers use Zeta Aquilae as a telluric standard star.[11] That is, the spectrum of this star is used to correct for telluric contamination from the Earth's atmosphere when examining the spectra of neighboring stars.[12] Observation of this star in the infrared band during the 2MASS survey appeared to reveal excess emission. However, the distribution of this emission couldn't be readily explained by a conjectured disk of circumstellar dust.[6] Instead, the detection was later ascribed to errors caused by saturation of the near-infrared detectors.[7]


Several faint nearby stars have been listed as companions to ζ Aquilae. The Catalog of Components of Double and Multiple Stars lists two 12th magnitude star at 6.5" and 160".[13] The Washington Double Star Catalog lists the same two 12th magnitude stars at 7.5" and 160", plus an 11th magnitude star separated by 200" and a more distant 16th magnitude star.[14]

In 2014 the star at 7.5" was identified as a binary companion with a mass of 0.5 M separated by 185 AU from the primary. The 16th magnitude star was also considered to be a co-moving companion with a mass of 0.14 M 38000 AU from the primary.[15]


It has the traditional names Deneb el Okab, from an Arabic term ذنب العقاب Dhanab Al-uqab meaning "the tail of the eagle", and the Mandarin names Woo and Yuë, derived from and represent the state Wu (吳), an old state was located at the mouth of the Yangtze River, and Yue (越), an old state in Zhejiang province[16] (together with 19 Capricorni in Ian Ridpath's version[17] or ψ Capricorni in R.H.Allen's version,[18] in Twelve States asterism). According to the R.H. Allen's works, it shares names with ε Aquilae.[19]

In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the left borderline of the enclosure, consisting of ζ Aquilae, δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, θ1 Serpentis, η Serpentis, ν Ophiuchi, ξ Serpentis and η Ophiuchi.[20] Consequently, ζ Aquilae itself is known as 天市左垣六 (Tiān Shì Zuǒ Yuán liù, English: the Sixth Star of Left Wall of Heavenly Market Enclosure), represent the states which have mentioned above.[21]

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Dzeneb al Tair (from ذنب الطائر - ðanab aṭ-ṭā’ir), which was translated into Latin as Cauda (Vulturis) Volantis, meaning the eagle's tail.[22]

In culture[edit]

The system is depicted in the computer games Descent II[23] and Elite: Dangerous.


  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 Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publ. Dept. Astron. Univ. Chile, Publicaciones Universidad de Chile, Department de Astronomy, 1: 1–17, Bibcode:1966PDAUC...1....1G 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819 
  4. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and their Applications. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E. 
  5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  6. ^ a b c d e Absil, O.; et al. (September 2008), "A near-infrared interferometric survey of debris disc stars. II. CHARA/FLUOR observations of six early-type dwarfs", Astronomy and Astrophysics, 487 (3): 1041–1054, arXiv:0806.4936Freely accessible, Bibcode:2008A&A...487.1041A, doi:10.1051/0004-6361:200810008 
  7. ^ a b c d e f g h Plavchan, Peter; et al. (June 2009), "New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope", The Astrophysical Journal, 698 (2): 1068–1094, arXiv:0904.0819Freely accessible, Bibcode:2009ApJ...698.1068P, doi:10.1088/0004-637X/698/2/1068 
  8. ^ Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M 
  9. ^ 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/0610785Freely accessible, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224 
  10. ^ "zet Aql -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-13 
  11. ^ Kiss, László L.; Vinkó, József (May 2000), "A photometric and spectroscopic study of the brightest northern Cepheids - III. A high-resolution view of Cepheid atmospheres", Monthly Notices of the Royal Astronomical Society, 314 (2): 420–432, arXiv:astro-ph/9912438Freely accessible, Bibcode:2000MNRAS.314..420K, doi:10.1046/j.1365-8711.2000.03375.x 
  12. ^ Niessen, P. E. (2008). "Quantitative spectroscopy with the UVES". In Kaufer, Andreas; Kerber, Florian. The 2007 ESO Instrument Calibration Workshop: Proceedings of the ESO Workshop Held in Garching, Germany, 23-26 January 2007. Eso Astrophysics Symposia. Springer. pp. 365–374. ISBN 3-540-76962-5. 
  13. ^ Dommanget, J; Nys, O (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. De l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D. 
  14. ^ Mason, Brian D; Wycoff, Gary L; Hartkopf, William I; Douglass, Geoffrey G; Worley, Charles E (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. 
  15. ^ De Rosa, R. J; Patience, J; Wilson, P. A; Schneider, A; Wiktorowicz, S. J; Vigan, A; Marois, C; Song, I; MacIntosh, B; Graham, J. R; Doyon, R; Bessell, M. S; Thomas, S; Lai, O (2014). "The VAST Survey - III. The multiplicity of A-type stars within 75 pc". Monthly Notices of the Royal Astronomical Society. 437 (2): 1216. arXiv:1311.7141Freely accessible. Bibcode:2014MNRAS.437.1216D. doi:10.1093/mnras/stt1932. 
  16. ^ (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived August 10, 2010, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. ^ Ian Ridpath's Startales - Capricornus the Sea Goat
  18. ^ Star Names - R.H.Allen p.142
  19. ^ Star Names - R.H.Allen p.61
  20. ^ (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.
  21. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived September 29, 2009, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
  22. ^ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429–438. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429. 
  23. ^ https://www.youtube.com/watch?v=KQCLZjyg07M#t=178s

External links[edit]