Astronomy:Iota Aquilae

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Short description: Star in the constellation Aquila
Iota Aquilae
Location of ι Aquilae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aquila[1]
Right ascension  19h 36m 43.2777s[2]
Declination −01° 17′ 11.759″[2]
Apparent magnitude (V) 4.364[3]
Characteristics
Spectral type B5 III[4] or B6 IV[5]
U−B color index −0.428[3]
B−V color index −0.083[3]
R−I color index −0.08[6]
Astrometry
Radial velocity (Rv)−21.34±3.63[2] km/s
Proper motion (μ) RA: −1.426[2] mas/yr
Dec.: −21.644[2] mas/yr
Parallax (π)5.6673 ± 0.1947[2] mas
Distance580 ± 20 ly
(176 ± 6 pc)
Absolute magnitude (MV)−1.01[1]
Details
Mass4.8±0.3[7] M☉
Radius7.8±0.9[8] R☉
Luminosity851[7] L☉
Surface gravity (log g)3.64±0.05[7] cgs
Temperature14,500±600[8] K
Metallicity [Fe/H]0.09±0.04[1] dex
Rotational velocity (v sin i)55[9] km/s
Age100 ± 8[7] Myr
Other designations
Al Thalimain, ι Aquilae, Iota Aql, ι Aql, 41 Aql, GC 27103, HD 184930, HIP 96468, HR 7447, SAO 143597, PPM 180738, WDS J19367-0117A[10]
Database references
SIMBADdata

Iota Aquilae is a star in the equatorial constellation of Aquila. Its identifier is a Bayer designation that is Latinized from ι Aquilae, and abbreviated Iota Aql or ι Aql. The star has the traditional name Al Thalimain, pronounced /ælˌθælɪˈmeɪn/, which it shares with λ Aquilae. The name is derived from the Arabic term الظليمین al-ẓalīmayn meaning "The Two Ostriches".[11] With an apparent visual magnitude of 4.364,[3] this star is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 5.67±0.19 mas,[2] it is located at a distance of around 580 light-years (180 parsecs) from Earth.[2] The visual magnitude of the star is diminished by 0.15 from extinction caused by intervening gas and dust.[7]

In 1968, this star was assigned a stellar classification of B5III,[4] which suggests it has exhausted its hydrogen supply at its core and evolved into a blue giant. However, stellar models from 2002 indicate it is around 100 million years old and has thus far spent 91% of its allotted lifetime on the main sequence.[7] In 2024, a study of standard stars suggested that Iota Aquilae be classified as B6 IV, matching a subgiant star.[5]

Iota Aquilae has nearly five times the mass of the Sun[7] and eight times the Sun's radius.[8] It is emitting 851 times the luminosity of the Sun from its outer atmosphere[7] at an effective temperature of 14,500 K,[12] giving it the blue-white hue of a B-type star.[13] The projected rotational velocity of this star is 55 km/s.[9]

Nomenclature

In Chinese, 右旗 (Yòu Qí), meaning Right Flag, refers to an asterism consisting of ι Aquilae, μ Aquilae, σ Aquilae, δ Aquilae, ν Aquilae, 42 Aquilae, HD 184701, κ Aquilae and 56 Aquilae.[14] Consequently, the Chinese name for ι Aquilae itself is 右旗五 (Yòu Qí wu, English: the Fifth Star of Right Flag.)[15]

This star, together with η Aql, θ Aql, δ Aql, κ Aql and λ Aql were once part of the obsolete constellation Antinous.[16]

References

  1. ↑ 1.0 1.1 1.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series 61: 387–405, Bibcode: 1985A&AS...61..387K. 
  4. ↑ 4.0 4.1 Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement 17: 371, doi:10.1086/190179, Bibcode: 1968ApJS...17..371L. 
  5. ↑ 5.0 5.1 Negueruela, I. et al. (2024), "The IACOB project: XII. New grid of northern standards for the spectral classification of B-type stars", Astronomy and Astrophysics 690: id. A176, doi:10.1051/0004-6361/202449298, Bibcode: 2024A&A...690A.176N. 
  6. ↑ Mallama, A. (2014), "Sloan Magnitudes for the Brightest Stars", Journal of the American Association of Variable Star Observers (Jaavso) 42 (2): 443, Bibcode: 2014JAVSO..42..443M. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Lyubimkov, Leonid S. et al. (June 2002), "Surface abundances of light elements for a large sample of early B-type stars - II. Basic parameters of 107 stars", Monthly Notices of the Royal Astronomical Society 333 (1): 9–26, doi:10.1046/j.1365-8711.2002.05341.x, Bibcode: 2002MNRAS.333....9L. 
  8. ↑ 8.0 8.1 8.2 Gordon, Kathryn D. et al. (March 2019), "Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array", The Astrophysical Journal 873 (1): 91, doi:10.3847/1538-4357/ab04b2, Bibcode: 2019ApJ...873...91G. 
  9. ↑ 9.0 9.1 Abt, Helmut A. et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 
  10. ↑ "iot Aql". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=iot+Aql. 
  11. ↑ "Patronage for Star #96165 | Patronize a star | OpenSea". https://opensea.io/ja/assets/ethereum/0xfbdc912795b7c5ba61a39d1c1b6d7277b008a79a/12. 
  12. ↑ 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, doi:10.1093/mnras/189.3.601, Bibcode: 1979MNRAS.189..601U. 
  13. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16. 
  14. ↑ Script error: The function "in_lang" does not exist. 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. ↑ "AEEA 天文教育資訊網". http://aeea.nmns.edu.tw/2006/0607/ap060703.html. 
  16. ↑ Ridpath, Ian, "Antinous", Ian Ridpath's Star Tales, http://www.ianridpath.com/startales/antinous.html, retrieved 2025-04-18. 



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