9 Cygni
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]
| 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[1] mas |
| Distance | 594 ± 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 | |
| Mass | 2.9±0.4[2] M☉ |
| Radius | 18.2[4] R☉ |
| Surface gravity (log g) | 3.040±0.370[5] cgs |
| Temperature | 5,047[4] K |
| Metallicity [Fe/H] | −0.260±0.090[5] dex |
| 9 Cyg B | |
| Mass | 2.7±0.4[2] M☉ |
| Radius | 3.5[4] R☉ |
| Temperature | 9,247[4] K |
| Age | 437.1[4] Myr |
| Other designations | |
| 9 Cyg A: HD 184759 | |
| 9 Cyg B: HD 184760 | |
| Database references | |
| SIMBAD | data |
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
- 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.
- 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.
- "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory.
- 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.
- 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.
- "* 9 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-28.
See also
- Spectroscopic binary