Sigma Cygni

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σ Cygni
Cygnus constellation map.svg
Red circle.svg

Location of σ Cygni (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 21h 17m 24.95244s[1]
Declination +39° 23′ 40.8528″[1]
Apparent magnitude (V) 4.233[2]
Spectral type B9 Iab[2]
U−B color index −0.386[2]
B−V color index +0.123[2]
Radial velocity (Rv) −5.30 ± 0.40[3] km/s
Proper motion (μ) RA: −0.13[1] mas/yr
Dec.: −3.58[1] mas/yr
Parallax (π) 1.13 ± 0.19[1] mas
Distance 1,000[4] pc
Absolute magnitude (MV) −6.18[4]
Mass 15[5] M
Radius 54[4] R
Luminosity 52,500[6] L
Surface gravity (log g) 1.85[2] cgs
Temperature 10.800[2] K
Metallicity 0.0[6]
Rotational velocity (v sin i) 14[2] km/s
Age 16[6] Myr
Other designations
67 Cyg, HD 202850, HR 8143, HIP 105102
Database references

Sigma Cygni (σ Cyg) is a supergiant star in the constellation Cygnus. Its apparent magnitude is 4.2. It is a blue supergiant. It belongs to the Cygnus OB4 stellar association and is located approximately 3,300 light years away from Earth.

Because of its location at the galactic disk, σ Cyg is obstructed by interstellar dust and is reddened by around 0.2 magnitudes and loses about 0.6 magnitudes at visual wavelengths.[2] Allowing for this, the star is over 50,000 times as luminous as the sun.

Spectral analysis of the star showed that photospheric SiII and HeI lines display a simultaneous, periodic variability. The periodicity was calculated at 1.59 hours in all three lines and it might by reasult of stellar oscillations.[7] No clear variation in the brightness has been detected.[8]


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f g h Firnstein, M.; Przybilla, N. (2012). "Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters". Astronomy & Astrophysics. 543: A80. arXiv:1207.0308free to read. Bibcode:2012A&A...543A..80F. doi:10.1051/0004-6361/201219034. 
  3. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. 
  4. ^ a b c Markova, N.; Puls, J. (2008). "Bright OB stars in the Galaxy. IV. Stellar and wind parameters of early to late B supergiants". Astronomy and Astrophysics. 478 (3): 823. arXiv:0711.1110free to read. Bibcode:2008A&A...478..823M. doi:10.1051/0004-6361:20077919. 
  5. ^ Przybilla, N.; Firnstein, M.; Nieva, M. F.; Meynet, G.; Maeder, A. (2010). "Mixing of CNO-cycled matter in massive stars". Astronomy and Astrophysics. 517: A38. arXiv:1005.2278free to read. Bibcode:2010A&A...517A..38P. doi:10.1051/0004-6361/201014164. 
  6. ^ a b c Tanrıverdi, Taner (2013). "Elemental abundances of the supergiant stars σ Cygnus and η Leonis". New Astronomy. 25: 50. arXiv:1512.04557free to read. Bibcode:2013NewA...25...50T. doi:10.1016/j.newast.2013.03.013. 
  7. ^ M. Kraus, S. Tomić, M. E. Oksala and M. Smole (June 2012). "Detection of a 1.59 h period in the B supergiant star HD 202850". Astronomy and Astrophysics. 542: L32. arXiv:1205.5391free to read. Bibcode:2012A&A...542L..32K. doi:10.1051/0004-6361/201219319. 
  8. ^ Koen, Chris; Eyer, Laurent (2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331: 45. arXiv:astro-ph/0112194free to read. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x.