Kappa Aquilae

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Kappa Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Cercle rouge 100%.svg

Location of κ Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 36m 53.44952s[1]
Declination –7° 01′ 38.9176″[1]
Apparent magnitude (V) +4.957[2]
Spectral type B0.5 III[3]
U−B color index –0.861[2]
B−V color index –0.028[2]
Radial velocity (Rv) –19.4[4] km/s
Proper motion (μ) RA: +1.63[1] mas/yr
Dec.: –2.65[1] mas/yr
Parallax (π) 1.94 ± 0.20[1] mas
Distance approx. 1,700 ly
(approx. 520 pc)
Mass 15.50 ± 0.61[5] M
Radius 12.5[6] R
Luminosity 52,630[5] L
Surface gravity (log g) 3.5[7] cgs
Temperature 26,500[5] K
Rotational velocity (v sin i) 265[8] km/s
Age 11.1 ± 0.5[3] Myr
Other designations
39 Aquilae, BD–07 5006, FK5 737, HD 184915, HIP 96483, HR 7446, SAO 143600.[9]

Kappa Aquilae (κ Aql, κ Aquilae) is the Bayer designation for a star in the equatorial constellation of Aquila. It is a faint star at apparent visual magnitude +4.957,[2] but bright enough to be seen with the naked eye in dark suburban skies. The annual parallax is only 1.94 mas,[1] which equates to a distance of approximately 1,700 light-years (520 parsecs) from Earth (with a 10% margin of error).

The spectrum of Kappa Aquilae matches a stellar classification of B0.5 III,[3] where the luminosity class of III is typically associated with evolved giant stars. This is a huge star with 15.50[5] times the Sun's mass and 12.5[6] times the radius of the Sun. Massive stars like this blaze brightly; it is radiating 52,630-fold[5] the Sun's luminosity from its outer atmosphere with a scorching effective temperature of 26,500 K,[5] giving it the intense blue-white glow of a B-type star. It is only 11 million years of age[3] and is spinning rapidly with a projected rotational velocity of 265 km/s.[8]


  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, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G. 
  3. ^ a b c d Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x. 
  4. ^ 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. 
  5. ^ a b c d e f Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335Freely accessible, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355. 
  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: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601. 
  7. ^ Frémat, Y.; et al. (September 2005), "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars", Astronomy and Astrophysics, 440 (1): 305–320, arXiv:astro-ph/0503381Freely accessible, Bibcode:2005A&A...440..305F, doi:10.1051/0004-6361:20042229. 
  8. ^ a b Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590. 
  9. ^ "kap Aql -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-13 

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