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9 Cygni is a binary star system in the northern constellation of Cygnus. 9 Cygni is its Flamsteed designation. The two stars have a combined magnitude of 5.39,[2] so it can be seen with the naked eye under good viewing conditions. Parallax measurements made by Gaia put the star at a distance of around 590 light-years (182 parsecs) away.[1]

9 Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 34m 50.9285s[1]
Declination +29° 27′ 46.697″[1]
Apparent magnitude (V) 5.39[2] (5.9 + 6.4)[3]
Characteristics
Evolutionary stage Red clump + main sequence[4]
Spectral type G8 IIIa + A2 V[4]
B−V color index 0.581[2]
Astrometry
Radial velocity (Rv)20.09±1.98[1] km/s
Proper motion (μ) RA: +14.822[1] mas/yr
Dec.: +13.554[1] mas/yr
Parallax (π)5.4904 ± 0.0892 mas[1]
Distance594 ± 10 ly
(182 ± 3 pc)
Absolute magnitude (MV)−0.70[2]
Orbit[3]
Period (P)4.56 yr
Semi-major axis (a)0.030″
Eccentricity (e)0.82
Inclination (i)114.6°
Longitude of the node (Ω)29.3°
Periastron epoch (T)1985.56
Argument of periastron (ω)
(secondary)		45.5°
Details
9 Cyg A
Mass2.9±0.4[2] M☉
Radius18.2[4] R☉
Surface gravity (log g)3.040±0.370[5] cgs
Temperature5,047[4] K
Metallicity [Fe/H]−0.260±0.090[5] dex
9 Cyg B
Mass2.7±0.4[2] M☉
Radius3.5[4] R☉
Temperature9,247[4] K
Age437.1[4] Myr
Other designations
BD+29 3651, HIP 96302, HR 7441, SAO 87385[6]
9 Cyg A: HD 184759
9 Cyg B: HD 184760
Database references
SIMBADdata

The two stars of 9 Cygni are a G-type giant and an A-type star. Both stars are over twice as massive as the Sun.[2] They orbit once every 4.56 years, separated with a semi-major axis of 0.030 arcseconds. However, the eccentricity is high, at 0.82.[3] The primary is a red clump giant, a star on the cool end of the horizontal branch fusing helium in its core. The secondary star has begun to evolve off the main sequence; it is sometimes classified as a giant star[2] and sometimes as a main-sequence star.[4]


References


  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. 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): 513–537. Bibcode:2002ApJS..143..513G. doi:10.1086/342942.
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory.
  4. Eggleton, Peter P.; Yakut, Kadri (2017). "Models for 60 double-lined binaries containing giants". Monthly Notices of the Royal Astronomical Society. 468 (3): 3533. arXiv:1611.05041. Bibcode:2017MNRAS.468.3533E. doi:10.1093/mnras/stx598. S2CID 119476544.
  5. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. S2CID 119258214.
  6. "* 9 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-28.

See also




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