Mu Cygni

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Mu Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension  21h 44m 08.57793s[1]
Declination 28° 44′ 33.4731″[1]
Apparent magnitude (V) 4.50[2]
Spectral type F6V + G2V[3]
B−V color index +0.47[2]
Radial velocity (Rv) +16.95[4] km/s
Proper motion (μ) RA: +260.72[2] mas/yr
Dec.: -243.21[2] mas/yr
Parallax (π) 44.97 ± 0.43[1] mas
Distance 72.5 ± 0.7 ly
(22.2 ± 0.2 pc)
μ1 Cyg
Absolute bolometric
μ2 Cyg
Absolute bolometric
Period (P) 789 yr
Semi-major axis (a) 5.32″
Eccentricity (e) 0.66
Inclination (i) 75.5°
Longitude of the node (Ω) 110.1°
Periastron epoch (T) 1958.0
Argument of periastron (ω)
μ1 Cyg
Mass 1.35 M
Radius 1.88±0.07 R
Surface gravity (log g) 4.05±0.10 cgs
Temperature 6,350±80 K
Metallicity [Fe/H] −0.18±0.07 dex
Rotational velocity (v sin i) 9.6±0.8 km/s
μ2 Cyg
Mass 1.02 M
Radius 1.08±0.05 R
Surface gravity (log g) 4.30±0.10 cgs
Temperature 6,055±100 K
Rotational velocity (v sin i) 2.5±1.0 km/s
Other designations
78 Cyg, BD+28° 4169, HIP 107310, CCDM J21442+2845AB, WDS J21441+2845AB[2]
μ1 Cyg: HD 206826, HR 8309, SAO 89940[7]
μ2 Cyg: HD 206827, HR 8310, SAO 89939[8]
Database references
μ1 Cyg
μ2 Cyg

μ Cygni (Latinised as Mu Cygni) is a binary star[9] in the constellation Cygnus. Located around 22.24 parsecs (72.5 ly) distant, the system has a combined apparent magnitude of 4.50.[2] The primary, with an apparent magnitude of 4.69, has a spectral type of F6V,[7] and the secondary, with an apparent magnitude of 6.12, has a spectral type of G2V.[8] Their orbit has a period of around 800 years, with a semimajor axis of 5" and an eccentricity around 0.6.[10]

Two reported additional components, C (apparent magnitude 12.93) and D (apparent magnitude 6.94), are believed to be optical doubles rather than part of the Mu Cygni system.[3] Component D is the more distant spectroscopic binary HD 206874 (HIP 107326), consisting of two early F-type subgiants.[11]


  1. ^ a b c van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c d e f "CCDM J21442+2845AB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-04-08.
  3. ^ a b Mason, Brian D.; et al. (December 2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920 Vizier catalog entry
  4. ^ Maldonado, J.; Martínez-Arnáiz, R. M.; Eiroa, C.; Montes, D.; Montesinos, B. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics, 521: A12, arXiv:1007.1132, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948
  5. ^ a b c Fuhrmann, Klaus (2011). "Nearby stars of the Galactic disc and halo - V". Monthly Notices of the Royal Astronomical Society. 414 (4): 2893. Bibcode:2011MNRAS.414.2893F. doi:10.1111/j.1365-2966.2011.18476.x.
  6. ^ Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2009yCat....102020P, doi:10.1051/0004-6361:20041213.
  7. ^ a b "HR 8309". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 January 2014.
  8. ^ a b "HR 8310". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 January 2014.
  9. ^ Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. Vizier catalog entry
  10. ^ Malkov, O. Yu.; et al. (October 2012), "Dynamical masses of a selected sample of orbital binaries", Astronomy & Astrophysics, 546 (A69): A69, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774 Vizier catalog entry
  11. ^ Abt, Helmut A (2009). "MK Classifications of Spectroscopic Binaries". The Astrophysical Journal Supplement. 180: 117. Bibcode:2009ApJS..180..117A. doi:10.1088/0067-0049/180/1/117.
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