Kappa Cygni

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

Location of κ Cygni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 19h 17m 06.16865s[1]
Declination +53° 22′ 06.4534″[1]
Apparent magnitude (V) 3.814[2]
Characteristics
Spectral type G9 III[3]
U−B color index +0.767[2]
B−V color index +0.965[2]
Astrometry
Radial velocity (Rv) –29.3[4] km/s
Proper motion (μ) RA: +60.07[1] mas/yr
Dec.: +122.83[1] mas/yr
Parallax (π) 26.27 ± 0.10[1] mas
Distance 124.2 ± 0.5 ly
(38.1 ± 0.1 pc)
Details
Radius 8–9[5] R
Surface gravity (log g) 2.7[6] cgs
Temperature 4,920[6] K
Metallicity [Fe/H] 0.13 ± 0.07[7] dex
Rotational velocity (v sin i) 3.7[6] km/s
Other designations
1 Cyg, BD+53 2216, FK5 726, HR 7328, HD 181276, SAO 31537, HIP 94779.

Kappa Cygni (κ Cyg) is a star in the northern constellation of Cygnus. It has an apparent visual magnitude of 3.8,[2] which is bright enough to be seen with the naked eye. In the constellation, it forms the tip of Cygnus the swan's left wing.[8] The radiant of the minor Kappa Cygnids meteor shower is located about 5° north of this star.[9]

Examination of this star's spectrum show it to match a stellar classification of G9 III,[3] with the 'III' luminosity class revealing that it has consumed the hydrogen fuel at its core and expanded into the giant star stage of its stellar evolution. It is known to vary in luminosity, but only by about 0.01 to 0.02 magnitudes.[10] The measured angular diameter of this star, after correction for limb darkening, is 2.07 ± 0.09 mas.[11] At an estimated distance of 124.2 light-years (38.1 parsecs) based on parallax measurements,[1] this yields a physical size of about 8–9 times the radius of the Sun.[5] The outer envelope has an effective temperature of 4,920 K,[6] giving it the yellow-orange hue of a star near the transition from a G- to a K-type classification.[12]

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 d Jennens, P. A.; Helfer, H. L. (September 1975), A new photometric metal abundance and luminosity calibration for field G and K giants., Monthly Notices of the Royal Astronomical Society 172: 667–679, Bibcode:1975MNRAS.172..667J 
  3. ^ a b Morgan, W. W.; Keenan, P. C. (1973), Spectral Classification, Annual Review of Astronomy and Astrophysics 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333 
  4. ^ Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions 35, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
    \begin{align} 2\cdot R_*
 & = \frac{(10^{-3}\cdot 38.1\cdot 2.07)\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
 & \approx 17\cdot R_{\bigodot}
\end{align}
  6. ^ a b c d Massarotti, Alessandro et al. (January 2008), Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity, The Astronomical Journal 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209 
  7. ^ Puzeras, E. et al. (October 2010), High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements, Monthly Notices of the Royal Astronomical Society 408 (2): 1225–1232, arXiv:1006.3857, Bibcode:2010MNRAS.408.1225P, doi:10.1111/j.1365-2966.2010.17195.x 
  8. ^ Consolmagno, Guy; Davis, Dan M. (2011), Turn Left at Orion: Hundreds of Night Sky Objects to See in a Home Telescope - and How to Find Them (4th ed.), Cambridge University Press, p. 134, ISBN 0-521-15397-2 
  9. ^ Stegmüller, Wolfgang (1979), The structuralist view of theories: a possible analogue of the Bourbaki programme in physical science, Astronomers' Observing Guides, Springer, p. 82, ISBN 0-387-09460-1 
  10. ^ Adelman, Saul J. (2001), On the Photometric Variability of Red Clump Giants, Baltic Astronomy 10: 593–597, Bibcode:2001BaltA..10..593A 
  11. ^ Richichi; Percheron, I.; Khristoforova, M. (February 2005), CHARM2: An updated Catalog of High Angular Resolution Measurements, Astronomy and Astrophysics 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039 
  12. ^ The Colour of Stars, Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16