Astronomy:9 Cygni

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Short description: Star in the constellation Cygnus
9 Cygni
Observation data
Equinox J2000.0]] (ICRS)
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[1] mas
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: {{{names1}}}
9 Cyg B: {{{names2}}}
Database references
SIMBADdata

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]

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. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 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. doi:10.1086/342942. Bibcode: 2002ApJS..143..513G. 
  3. ↑ 3.0 3.1 3.2 "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Eggleton, Peter P.; Yakut, Kadri (2017). "Models for 60 double-lined binaries containing giants". Monthly Notices of the Royal Astronomical Society 468 (3): 3533. doi:10.1093/mnras/stx598. Bibcode: 2017MNRAS.468.3533E. 
  5. ↑ 5.0 5.1 Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics 591: A118. doi:10.1051/0004-6361/201628497. Bibcode: 2016A&A...591A.118S. 
  6. ↑ "* 9 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+9+Cyg. 

See also



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