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Template:PAGEBANNER:Deneb Sun comparison small.png

Cygnus constellation map.png
Cygnus, the constellation in which Deneb is located.
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Pronunciation /ˈdɛnɛb/, /ˈdɛnəb/[1]
Right ascension 20h 41m 25.9s[2]
Declination +45° 16′ 49″[2]
Apparent magnitude (V) 1.25[3] (1.21 - 1.29[4])
Spectral type A2 Ia[5]
U−B color index −0.23[3]
B−V color index +0.09[3]
Variable type Alpha Cyg[4]
Radial velocity (Rv)−4.5[6] km/s
Proper motion (μ) RA: 1.99[2] mas/yr
Dec.: 1.95[2] mas/yr
Parallax (π)2.29 ± 0.32[2] mas
Distance802 ± 66[7] pc
Absolute magnitude (MV)−8.38[7]
Mass19 ± 4[7] M
Radius203 ± 17[7] R
Diameter203 ± 17[7] D
Luminosity196,000 ± 32,000[7] L
Surface gravity (log g)1.10 ± 0.05[7] cgs
Temperature8,525 ± 75[7] K
Metallicity [Fe/H]-0.25[7] dex
Rotational velocity (v sin i)20 ± 2[7] km/s
Other designations
α Cygni, Alpha Cyg, 50 Cyg, Arided, Aridif, Gallina, Arrioph, HR 7924, BD +44°3541, HD 197345, SAO 49941, FK5 777, HIP 102098.
Database references

Deneb, also designated α Cygni (Latinised as alpha Cygni, abbreviated Alpha Cyg, α Cyg and Arided), is the brightest star in the Cygnus constellation. It is the 19th brightest star with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the luminous stars, but its exact distance and luminosity have both been difficult to calculate. Deneb is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun, rivalling the similar star Rigel as the most inherently luminous star of first magnitude.[8] Deneb is only visible in the Northern hemisphere - it is not visible anywhere in Icons-flag-aq.png Antarctica and is expected to become the Pole star in around 9800 AD.

Distance and properties

Deneb's place near thetop centre on the Hertzsprung-Russell diagram.

Deneb's exact distance from the Earth is still uncertain. The currently accepted distance of around 2,600 light-years is derived by a variety of methods, including spectral luminosity classes, atmospheric modelling, stellar evolution models, assumed membership of the Cygnus OB7 association, and direct measurements of angular diameter. Deneb's absolute magnitude is currently estimated to be −8.4, placing it among the most luminous stars known, with an estimated luminosity nearly 200,000 times that of the Sun. This is towards the upper end of various published values over the last few decades.[8][9][10]

Deneb is the most luminous of the stars with apparent magnitude of < 1.5, and the most distant, by a factor of < 2 of the 30 brightest stars. Based on its temperature and luminosity, and also on direct measurements of its tiny angular diameter which is a mere 0.002 arcseconds, Deneb appears to have a diameter of about over 200 times that of the Sun;[8] if placed at the center of the Solar System, Deneb would extend out to the orbit of the Earth. It is one of the largest known white stars. Deneb is a blue star of spectral type A2Ia, with a surface temperature of around 8,500 degrees Kelvin. Since 1943, its spectrum has served as one of the stable reference stars by which other stars are classified.[5]


  1. Merriam-Webster's Collegiate Dictionary, Tenth Edition (1999)
  2. 2.0 2.1 2.2 2.3 2.4 Cite error: Invalid <ref> tag; no text was provided for refs named hipparcos
  3. 3.0 3.1 3.2 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237: 0. Bibcode 2002yCat.2237....0D.
  4. 4.0 4.1 Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1: 02025. Bibcode 2009yCat....102025S.
  5. 5.0 5.1 Garrison, R. F. (1993). "Anchor Points for the MK System of Spectral Classification". Bulletin of the American Astronomical Society 25: 1319. Bibcode 1993AAS...183.1710G. Retrieved 2012-02-04.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759. arXiv:1606.08053. Bibcode 2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 Schiller, F.; Przybilla, N. (2008). "Quantitative spectroscopy of Deneb". Astronomy & Astrophysics 479 (3): 849–858. arXiv:0712.0040. Bibcode 2008A&A...479..849S. doi:10.1051/0004-6361:20078590.
  8. 8.0 8.1 8.2 Chesneau, O.; Dessart, L.; Mourard, D.; Bério, Ph.; Buil, Ch.; Bonneau, D.; Borges Fernandes, M.; Clausse, J. M. et al. (2010). "Time, spatial, and spectral resolution of the Hα line-formation region of Deneb and Rigel with the VEGA/CHARA interferometer". Astronomy and Astrophysics 521: A5. arXiv:1007.2095. Bibcode 2010A&A...521A...5C. doi:10.1051/0004-6361/201014509.
  9. van de Kamp, P. (1953). "The Twenty Brightest Stars". Publications of the Astronomical Society of the Pacific 65: 30. Bibcode 1953PASP...65...30V. doi:10.1086/126523.
  10. Lamers, H. J. G. L. M.; Stalio, R.; Kondo, Y. (1978). "A study of mass loss from the mid-ultraviolet spectrum of α Cygni (A2 Ia), β Orionis (B8 Ia), and η Leonis (A0 Ib)". The Astrophysical Journal 223: 207. Bibcode 1978ApJ...223..207L. doi:10.1086/156252.