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
- ^ a b c d e f g 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.
- ^ a b c d e f g h 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.
- ^ a b c "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 2017-08-01. Retrieved 2020-02-29.
- ^ a b c d e f g h 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.
- ^ a b 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.
- ^ "* 9 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-28.