21 Aquilae

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21 Aquilae
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 13m 42.70359s[1]
Declination +02° 17′ 37.3403″[1]
Apparent magnitude (V) 5.140[2]
Spectral type B8 II-III[3]
U−B color index –0.399[2]
B−V color index –0.065[2]
Variable type α2 CVn
Radial velocity (Rv) –5.2[4] km/s
Proper motion (μ) RA: +6.95[1] mas/yr
Dec.: –3.28[1] mas/yr
Parallax (π) 4.59 ± 0.29[1] mas
Distance 710 ± 40 ly
(220 ± 10 pc)
Radius 4.3[5] R
Surface gravity (log g) 3.27[3] cgs
Temperature 13,175[3] K
Metallicity [Fe/H] –0.14[3] dex
Other designations
V1288 Aql, BD+02° 3824, FK5 3537, HD 179761, HIP 94477, HR 7287, SAO 124408.[6]
Database references

21 Aquilae (abbreviated 21 Aql) is a star in the equatorial constellation of Aquila. 21 Aquilae is its Flamsteed designation. Its apparent magnitude is 5.14[2] and it is located at a distance of around 710 light-years (220 parsecs) from Earth, give or take a 40 light-year margin of error.[1] The stellar classification of this star is B8 II-III,[3] with the luminosity class of II-III suggesting that the spectrum displays elements of both a giant star and a bright giant. The outer atmosphere has an effective temperature of 13,175 K;[3] this searing heat gives it the blue-white glow of a B-type star.[7]


  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 Stepien, K. (December 1968), "Photometric behavior of magnetic stars", Astrophysical Journal, 154: 945, Bibcode:1968ApJ...154..945S, doi:10.1086/149815. 
  3. ^ a b c d e f Cenarro, A. J.; et al. (January 2007), "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters", Monthly Notices of the Royal Astronomical Society, 374 (2): 664–690, arXiv:astro-ph/0611618Freely accessible, Bibcode:2007MNRAS.374..664C, doi:10.1111/j.1365-2966.2006.11196.x. 
  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, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E. 
  5. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  6. ^ "V1288 Aql -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-26. 
  7. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16 

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