47 Cygni

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47 Cygni
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 33m 54.18702s[1]
Declination +35° 15′ 03.0659″[1]
Apparent magnitude (V) 4.61[2]
Absolute magnitude (V)−4.1 (−4 + −1.5)[2]
Distance929[2] ly
(285 pc)
Spectral typeK6Ib + B3V[2]
Database references

47 Cygni (47 Cyg) is a double star in the constellation Cygnus. Its apparent magnitude is 4.66.

The two stars of 47 Cygni are separated by less than an arcsecond.[3] The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes.[4] The secondary is a hot B class main sequence star, but still 2.5 magnitudes fainter than the primary.


  1. 1.0 1.1 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653. arXiv:0708.1752. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 2.0 2.1 2.2 2.3 Ginestet, N.; Carquillat, J. M. (2002). "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components". The Astrophysical Journal Supplement Series 143 (2): 513. Bibcode 2002ApJS..143..513G. doi:10.1086/342942.
  3. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. Bibcode 2001AJ....122.3466M. doi:10.1086/323920.
  4. 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. Bibcode 2009yCat....102025S.

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