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Kappa Cygni

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κ Cygni
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
Evolutionary stage horizontal branch[3][4]
Spectral type G9 III[5]
U−B color index +0.767[2]
B−V color index +0.965[2]
Astrometry
Radial velocity (Rv)−29.36±0.09[6] 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]
Distance124.2 ± 0.5 ly
(38.1 ± 0.1 pc)
Absolute magnitude (MV)+0.84[6]
Details[7]
Mass2.19+0.14
−0.07 M☉
Radius8.65±0.10 R☉
Luminosity44.5±1.4 L☉
Surface gravity (log g)2.878+0.007
−0.004 cgs
Temperature5,066+50
−47 K
Metallicity [Fe/H]+0.06+0.10
−0.13 dex
Rotational velocity (v sin i)1.08±0.28[6] km/s
Age0.88+0.11
−0.15 Gyr
Other designations
κ Cyg, 1 Cygni, BD+53°2216, FK5 726, HD 181276, HIP 94779, HR 7328, SAO 31537
Database references
SIMBADdata

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.[8] The radiant of the minor Kappa Cygnids meteor shower is located about 5° north of this star.[9]

Kappa Cygni has been reported to vary in brightness between magnitudes 3.76 and 3.82, but this has not been confirmed and it is not formally catalogued as a variable star. It is tentatively classified as a type SRd semiregular variable star with a possible period around 79 days.[10] Hipparcos photometry indicated variability, but only by about 0.01 to 0.02 magnitudes which is potentially within the margin of error for a constant star.[11] TESS data at two-minute intervals over a two-year period indicates variability of only 90 parts per million, but with a possible period of 0.9 days.[12]

Examination of this star's spectrum show it to match a stellar classification of G9 III,[5] 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. Despite being younger than the Sun with an age of 880 million years, it has reached its current evolutionary stage because more massive stars evolve faster. Kappa Cygni has expanded to 8.65 times the Sun's radius and is glowing with 44.5 times the Sun's luminosity. The outer envelope has an effective temperature of 5,066 K,[7] giving it the yellow-orange hue of a star near the transition from a G- to a K-type classification.[13]

References

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  1. ^ a b c d e 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. ^ Stock, Stephan; Reffert, Sabine; Quirrenbach, Andreas (2018), "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search", Astronomy and Astrophysics, 616: A33, arXiv:1805.04094, Bibcode:2018A&A...616A..33S, doi:10.1051/0004-6361/201833111
  4. ^ Afşar, Melike; Bozkurt, Zeynep; Böcek Topcu, Gamze; Casetti-Dinescu, Dana I.; Sneden, Christopher; Şehitog̅Lu, Gizem (2018), "A Spectroscopic Survey of Field Red Horizontal-branch Stars", The Astronomical Journal, 155 (6): 240, arXiv:1804.04477, Bibcode:2018AJ....155..240A, doi:10.3847/1538-3881/aabe86
  5. ^ 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
  6. ^ a b c Deka-Szymankiewicz, B.; Niedzielski, A.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (2018-07-01), "The Penn State - Toruń Centre for Astronomy Planet Search stars. IV. Dwarfs and the complete sample", Astronomy and Astrophysics, 615: A31, arXiv:1801.02899, Bibcode:2018A&A...615A..31D, doi:10.1051/0004-6361/201731696, ISSN 0004-6361 Kappa Cygni's database entry at VizieR.
  7. ^ a b Chowhan, Arnab; Bedding, Timothy R.; Huber, Daniel; Ong, J. M. Joel; Schimak, Lea S.; Li, Yaguang; Crawford, Courtney L.; White, Timothy R. (2026-04-16), "CHARA Interferometry and TESS Asteroseismology of the Core-Helium Burning Red Giant κ Cyg", Monthly Notices of the Royal Astronomical Society, arXiv:2604.13501
  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 978-0-521-15397-3
  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. ^ "NNSV 11886". International Variable Star Index. AAVSO. Retrieved 2026-04-17.
  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. ^ Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel; Jenkins, Jon M.; Stassun, Keivan; Twicken, Joseph D.; Vanderspek, Roland; Winn, Joshua N. (2023). "Variability Catalog of Stars Observed during the TESS Prime Mission". The Astrophysical Journal Supplement Series. 268 (1): 4. arXiv:2208.11721. Bibcode:2023ApJS..268....4F. doi:10.3847/1538-4365/acdee5.
  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