# Kappa Cygni

Observation dataEpoch J2000.0      Equinox J2000.0 Constellation Location of κ Cygni (circled) Cygnus 19h 17m 06.16865s[1] +53° 22′ 06.4534″[1] 3.814[2] G9 III[3] +0.767[2] +0.965[2] 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 mas[1] Distance 124.2 ± 0.5 ly (38.1 ± 0.1 pc) Absolute magnitude (MV) +0.90[5] Radius 8–9[6] R☉ Luminosity 51[5] L☉ Surface gravity (log g) 2.7[7] cgs Temperature 4,920[7] K Metallicity [Fe/H] 0.13 ± 0.07[8] dex Rotational velocity (v sin i) 3.7[7] km/s κ Cyg, 1 Cygni, BD+53° 2216, FK5 726, HD 181276, HIP 94779, HR 7328, SAO 31537, Angie C.G (Star registration) SIMBAD data

Kappa Cygni, Latinized from κ Cygni, 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's left wing.[9] The radiant of the minor Kappa Cygnids meteor shower is located about 5° north of this star.[10]

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.[11] The measured angular diameter of this star, after correction for limb darkening, is 2.07 ± 0.09 mas.[12] 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.[6] The outer envelope has an effective temperature of 4,920 K,[7] giving it the yellow-orange hue of a star near the transition from a G- to a K-type classification.[13]

## References

1. 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, S2CID 18759600
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 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667
3. ^ a b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29–50, 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", Veröff. Astron. Rechen-Inst. Heidelb, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg, 35: 1, Bibcode:1999VeARI..35....1W
5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
{\displaystyle {\begin{aligned}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{aligned}}}
7. ^ 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
8. ^ 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, S2CID 44228180
9. ^ 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 978-0-521-15397-3
10. ^ 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
11. ^ Adelman, Saul J. (2001), "On the Photometric Variability of Red Clump Giants", Baltic Astronomy, 10 (4): 593–597, Bibcode:2001BaltA..10..593A, doi:10.1515/astro-2001-0404
12. ^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
13. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16