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Position beta Cyg.png
Albireo's position, lower right corner.
The cross-like figure is the Northern Cross.
The blue line shows the boundaries of the constellation the Swan.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Albireo Aa
Right ascension 19h 30m 43.286s
Declination +27° 57′ 34.84″[1]
Apparent magnitude (V) 3.18[2]
Albireo Ac
Right ascension 19h 30m 43.295s
Declination +27° 57′ 34.62″[3]
Apparent magnitude (V) 5.82[2]
Albireo B
Right ascension 19h 30m 45.3954s[4]
Declination +27° 57′ 54.995″[4]
Apparent magnitude (V) 5.09[4]
Albireo Aa
Spectral type K2II[5]
B−V color index 1.074[1]
V−R color index 0.92[2]
Albireo Ac
Spectral type B8:p[5]
B−V color index 0.09[3]
V−R color index 0.09[2]
Albireo B
Spectral type B8Ve[4]
U−B color index -0.30[6]
B−V color index -0.06[4]
Radial velocity (Rv) -24.07 km/s
Proper motion (μ) RA: -7.17 mas/yr
Dec.: -6.15 mas/yr
Parallax (π) 7.51 ± 0.33[7][a] mas
Distance 430 ± 20 ly
(133 ± 6 pc)
Albireo Aa
Absolute magnitude (MV) −2.45[5]
Albireo Ac
Absolute magnitude (MV) −0.25[5]
Radial velocity (Rv) -18[4] km/s
Proper motion (μ) RA: -1.95[4] mas/yr
Dec.: -0.98[4] mas/yr
Parallax (π) 8.16 ± 0.25[4][a] mas
Distance 400 ± 10 ly
(123 ± 4 pc)
Orbit (Aa/Ac)[8]
Period (P) 213.859 yr
Semi-major axis (a) 0.536
Eccentricity (e) 0.256
Inclination (i) 154.9°
Longitude of the node (Ω) 170.4°
Periastron epoch (T) B1997.995
Argument of periastron (ω)
Albireo Aa
Mass 5[9] M
Radius 70 R
Luminosity (bolometric) 1,200 L
Temperature 4,080±10[2] K
Albireo Ac
Mass 3.2[9] M
Radius 3.5 R
Luminosity (bolometric) 230 L
Temperature ~12,000[5] K
Mass 3.7 ± 0.8[10] M
Radius 2.7[11] R
Luminosity (bolometric) 230 ± 90[10] L
Surface gravity (log g) 4.00 ± 0.15[10] cgs
Temperature 13200 ± 600[10] K
Rotation <0.6 days[9]
Age 4×107 to 2×108 [10] years
Position (relative to Albireo A)
Component AlbireoB
Epoch of observation 2006
Angular distance 35.3 [12]
Position angle 54° [12]
Other designations
β Cygni, 6 Cygni, ADS 12540, CCDM J19307+2758, WDS 19307+2758[7][8][13]
AlbireoA: β1 Cygni, BD+27 3410, HR 7417, HD 183912/183913, HIP 95947, SAO 87301, FK5 732, MCA 55 Aac, NSV 12105
AlbireoB: β2 Cygni, STF 4043B, BD+27 3411, HD 183914, HIP 95951, HR 7418, SAO 87302[4]
Database references
SIMBAD AlbireoA data
AlbireoB data2

Albireo (β Cyg, β Cygni, Beta Cyg, Beta Cygni) is the fifth brightest star in the constellation Cygnus. Although it has the Bayer designation beta, it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni. Albireo appears to the naked eye to be a single star of magnitude 3 but through a telescope, even low magnification views resolve it into a double star. The brighter yellow star (actually itself a very close binary system) makes a striking colour contrast with its fainter blue companion star.[9]

Albireo B (top left) and
Albireo A (bottom right)

Double star[edit]

Albireo is about 430 light-years (130 pc)[a] away from the Earth. When viewed with the naked eye, it appears to be a single star. However, in a telescope it readily resolves into a double star, consisting of Albireo A (amber, apparent magnitude 3.1), and Albireo B (blue-green, apparent magnitude 5.1).[14] Separated by 35 seconds of arc,[12] the two components provide one of the best contrasting double stars in the sky due to their different colors. It is not known whether the two components are orbiting around each other in a physical binary system. If they are, their orbital period is probably at least 100,000 years.[14]

Albireo A[edit]

The spectrum of β Cygni A was found to be composite when it was observed as part of the Henry Draper Memorial project in the late 19th century, leading to the supposition that it was itself double.[15] This was supported by observations from 1898 to 1918 which showed that β Cygni A had a varying radial velocity.[16] In 1923, the components now called Albireo Aa and Albireo Ac were identified in the Henry Draper Catalogue as HD 183912 and HD 183913 respectively.[17][18] In 1976 speckle interferometry was used to resolve the pair at the 2.1-meter telescope at the Kitt Peak National Observatory.[13][19] It is also listed in the Washington Double Star Catalog.[8] An orbit for the pair has since been computed using interferometric measurements, but as only approximately a quarter of the orbit has been observed, the orbital parameters must be regarded as preliminary. The period of this orbit is 213 years.[13] The current angular separation between the components is around 0.4 arcseconds, too close to be visually resolved except with instruments of at least 20" in aperture with exceptionally stable atmospheric conditions.

Albireo B[edit]

Albireo B is a fast-rotating Be star, with an equatorial rotational velocity of at least 250 kilometers per second.[9] Its surface temperature has been spectroscopically estimated to be about 13,200 K.[10]

Names and etymology[edit]

Since Cygnus is the swan, and Albireo is located at the head of the swan, Albireo is sometimes called the "beak star".[20] With Deneb, Sadr, Delta Cygni, and Gienah, it forms the asterism called the Northern Cross.[21]

Medieval Arabic-speaking astronomers called Albireo minqār al-dajājah (English: the hen's beak).[22] Its current name is a result of misunderstanding and mistranslation. It is thought that it originated in the Greek name ornis for the constellation of Cygnus, which became urnis in Arabic.[23] When translated into Latin, this name was thought to refer to the plant Erysimum officinale, and so was translated into a Latin name for this plant, ireo. The phrase ab ireo was later treated as a misprint of an Arabic term and transcribed as al-bireo.[24]

The term minqār al-dajājah (منقار الدجاجة) or Menchir al Dedjadjet appeared in the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, which was translated into Latin as Rostrum Gallinǣ, meaning the hen's beak.[25]


USS Albireo (AK-90) was a United States Navy Crater class cargo ship named after the star.


  1. ^ a b c The primary and secondary have different formal Hipparchos parallaxes. They are thought to be physically related and so at the same distance from Earth in astronomical terms, hence one or both derived distances are somewhat in error.


  1. ^ a b [1], Hipparcos catalogue; CDS.
  2. ^ a b c d e Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory, Theo ten Brummelaar, Brian D. Mason, et al., Astronomical Journal 119, #5 (May 2000), pp. 2403–2414. doi:10.1086/301338. Bibcode2000AJ....119.2403T . See tables 4, 5, 6, and 8. Luminosity from Lbol=102(4.75−Mbol)/5.
  3. ^ a b [2], Hipparcos catalogue; CDS.
  4. ^ a b c d e f g h i j HD 183914 -- Emission-line Star, database entry, SIMBAD. Accessed on line July 9, 2008.
  5. ^ a b c d e 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. 
  6. ^ UBV observations of visual double stars, T. E. Lutz, Publications of the Astronomical Society of the Pacific 83 (August 1971), pp. 488–490. Bibcode1971PASP...83..488L .
  7. ^ a b NAME ALBIREO -- Star in double system , database entry, SIMBAD. Accessed on line July 9, 2008.
  8. ^ a b c Entry, WDS identifier 19307+2758, Sixth Catalog of Orbits of Visual Binary Stars, William I. Hartkopf & Brian D. Mason, U.S. Naval Observatory. Accessed on line July 9, 2008. (19307+2758)
  9. ^ a b c d e Albireo, Stars, Jim Kaler. Accessed on line October 23, 2013.
  10. ^ a b c d e f Table 1, Physical Parameters of Southern B- and Be-Type Stars, R. S. Levenhagen and N. V. Leister, The Astronomical Journal 127, #2 (February 2004), pp. 1176–1180, doi:10.1086/381063, Bibcode2004AJ....127.1176L .
  11. ^ Entry, HD 183914, Catalogue of Stellar Diameters (CADARS); CDS ID II/224.
  12. ^ a b c Entry, The Washington Double Star Catalog, identifier 19307+2758, discoverer identifier STFA 43. Accessed on line July 9, 2008. Archived 8 September 2008 at the Wayback Machine.
  13. ^ a b c Speckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005, M. Scardia et al., Astronomische Nachrichten 329, #1 (2008), pp. 54–68. Bibcode2008AN....329...54S . doi:10.1002/asna.200710834.
  14. ^ a b p. 46, The Monthly Sky Guide, Ian Ridpath, Wil Tirion, Cambridge University Press, 2006, ISBN 0-521-68435-8.
  15. ^ note 145, p. 99, "Spectra of bright stars photographed with the 11-inch Draper Telescope as part of the Henry Draper Memorial", Antonia C. Maury and Edward C. Pickering, Annals of the Astronomical Observatory of Harvard College 28 (1897), pp. 1-128, Bibcode1897AnHar..28....1M .
  16. ^ "The Variable Velocity of β Cygni", W. W. Campbell, Publications of the Astronomical Society of the Pacific 31, #179, pp. 38-39, Bibcode1919PASP...31...38C .
  17. ^ freestarcharts dot com
  18. ^ p. 251, "The Henry Draper Catalogue: 19h and 20h", Annie J. Cannon & Edward C. Pickering, Annals of the Astronomical Observatory of Harvard College 98 (1923), Bibcode1923AnHar..98....1C . See note re HD 183912,3,4 on this page.
  19. ^ Speckle interferometric measurements of binary stars. VI, H. A. McAlister and E. M. Hendry, Astrophysical Journal Supplement Series 48 (March 1982), pp. 273–278. Bibcode1982ApJS...48..273M . doi:10.1086/190778.
  20. ^ p. 416, In Quest of the Universe, Theo Koupelis and Karl F. Kuhn, 5th ed., Sudbury, Massachusetts: Jones & Bartlett Publishers, 2007, ISBN 0-7637-4387-9.
  21. ^ Northern Cross, entry, The Internet Encyclopedia of Science, David Darling. Accessed on line July 24, 2008.
  22. ^ p. 196, Star-names and Their Meanings, Richard Hinckley Allen, New York, G. E. Stechert, 1899.
  23. ^ p. 24, The names of the stars and constellations compiled from the Latin, Greek and Arabic, W. H. Higgins, Leicester: Samuel Clarke, 1882.
  24. ^ p. 194, Allen.
  25. ^ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429. 

External links[edit]