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 blue supergiant star in the constellation Cygnus. Its apparent magnitude is 4.2. 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 be the result 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. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. 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. Bibcode:2012A&A...543A..80F. arXiv:1207.0308Freely accessible. 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. arXiv:1606.08053Freely accessible. 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. Bibcode:2008A&A...478..823M. arXiv:0711.1110Freely accessible. 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. Bibcode:2010A&A...517A..38P. arXiv:1005.2278Freely accessible. 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. Bibcode:2013NewA...25...50T. arXiv:1512.04557Freely accessible. doi:10.1016/j.newast.2013.03.013. 
  7. ^ Kraus, M.; Tomić, S.; Oksala, M. E.; Smole, M. (June 2012). "Detection of a 1.59 h period in the B supergiant star HD 202850". Astronomy and Astrophysics. 542: L32. Bibcode:2012A&A...542L..32K. arXiv:1205.5391Freely accessible. 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. Bibcode:2002MNRAS.331...45K. arXiv:astro-ph/0112194Freely accessible. doi:10.1046/j.1365-8711.2002.05150.x.