Epoch J2000.0 Equinox J2000.0
|16 Cygni A|
|Right ascension||19h 41m 48.95s|
|Declination||+50° 31′ 30.2″|
|Apparent magnitude (V)||5.96|
|16 Cygni B|
|Right ascension||19h 41m 51.97s|
|Declination||+50° 31′ 03.1″|
|Apparent magnitude (V)||6.20|
|Spectral type||G1.5Vb / G2.5Vb / M?V|
|U−B color index||0.19 / 0.20|
|B−V color index||0.64 / 0.66|
|16 Cyg A|
|Proper motion (μ)||RA: -147.82 ± 0.30 mas/yr
Dec.: -159.01 ± 0.28 mas/yr
|Parallax (π)||47.44 ± 0.27 mas|
|Distance||68.8 ± 0.4 ly
(21.1 ± 0.1 pc)
|Absolute magnitude (MV)||4.29|
|16 Cyg B|
|Proper motion (μ)||RA: 135.11 mas/yr
Dec.: -163.78 mas/yr
|Parallax (π)||47.14 ± 0.27 mas|
|Distance||69.2 ± 0.4 ly
(21.2 ± 0.1 pc)
|Absolute magnitude (MV)||4.53|
|16 Cyg A|
|Temperature||5,803 ± 3.1 K|
|16 Cyg B|
|Temperature||5,752 ± 3.5 K|
16 Cygni or 16 Cyg is a triple star system approximately 69 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B.
The parallax of the two brightest stars were measured as part of the Hipparcos astrometry mission. This yielded a parallax of 47.44 milliarcseconds for 16 Cygni A and 47.14 milliarcseconds for 16 Cygni B. Since the two components are associated, it is reasonable to assume they lie at the same distance, so the different parallaxes are a result of experimental error (indeed, when the associated parallax errors are taken into account, the ranges of the parallaxes overlap). Using the parallax of the A component, the distance is 21.1 parsecs. The parallax of the B component corresponds to a distance of 21.2 parsecs.
Stellar components 
16 Cygni is a hierarchal triple system. Stars A and C form a close binary with a projected separation of 73 AU. The orbital elements of the A–C binary are currently unknown. At a distance of 860 AU from A is a third component designated 16 Cygni B. The orbit of B relative to the A–C pair was determined in 1999 and not updated since (as of June 2007): plausible orbits range in period from 18,200 to 1.3 million years, with a semimajor axis ranging from 877 to 15,180 AU. In addition B orbits between 100 and 160 degrees inclination, that is against the A–C pole such that 90 degrees would be ecliptical.
Both 16 Cygni A and 16 Cygni B are yellow dwarf stars like our Sun. According to data from the Geneva–Copenhagen survey, both stars have masses similar to the Sun. Age estimates for the two stars vary slightly, but 16 Cygni is likely to be much older than the Solar System, at around 10,000 million years old. 16 Cygni C is much fainter than either of these stars, and may be a red dwarf.
Planetary system 
Like the majority of extrasolar planets detectable from Earth, 16 Cygni Bb was deduced from the radial velocity of its parent star. At the time that only gave a lower limit on the mass: in this case, about 1.68 times that of Jupiter. In 2012, two astronomers, E. Plavalova and N.A. Solovaya, showed that the stable orbit would demand about 2.38 Jupiter masses, such that its orbit was inclined at either 45 or 135 degrees.
"For the 16 Cyg B system, only particles inside of about 0.3 AU remained stable [within a million years of formation], leaving open the possibility of short-period planets". For them, observation rules out any such planet of over a Neptune mass.
There was a METI message sent to the 16 Cygni system. It was transmitted from Eurasia's largest radar – 70-meter (230-foot) Eupatoria Planetary Radar. The message was named Cosmic Call 1, it was sent on May 24, 1999, and it will arrive at 16 Cygni in November 2069.
(in order from star)
|b||2.38 ± 0.04 MJ||1.693||799.5||0.689 ± 0.011||—||—|
See also 
- 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 for A Vizier catalog entry for B
- Kovtyukh et al.; Soubiran, C.; Belik, S. I.; Gorlova, N. I. (2003). "High precision effective temperatures for 181 F-K dwarfs from line-depth ratios". Astronomy and Astrophysics 411 (3): 559–564. arXiv:astro-ph/0308429. Bibcode:2003A&A...411..559K. doi:10.1051/0004-6361:20031378.
- Raghavan et al.; Henry, Todd J.; Mason, Brian D.; Subasavage, John P.; Jao, Wei‐Chun; Beaulieu, Thom D.; Hambly, Nigel C. (2006). "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems". The Astrophysical Journal 646 (1): 523–542. arXiv:astro-ph/0603836. Bibcode:2006ApJ...646..523R. doi:10.1086/504823.
- Hauser, H., Marcy, G. (1999). "The Orbit of 16 Cygni AB". Publications of the Astronomical Society of the Pacific 111 (757): 321–334. Bibcode:1999PASP..111..321H. doi:10.1086/316328.
- Holmberg et al. (2007). "Record 13627". Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved 19 November 2008.
- Holmberg et al. (2007). "Record 13631". Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved 19 November 2008.
- Cochran et al.; Hatzes, Artie P.; Butler, R. Paul; Marcy, Geoffrey W. (1997). "The Discovery of a Planetary Companion to 16 Cygni B". The Astrophysical Journal 483 (1): 457–463. arXiv:astro-ph/9611230. Bibcode:1997ApJ...483..457C. doi:10.1086/304245.
- Butler et al.; Wright, J. T.; Marcy, G. W.; Fischer, D. A.; Vogt, S. S.; Tinney, C. G.; Jones, H. R. A.; Carter, B. D. et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701.
- E. Plávalová, N. A. Solovaya (2012). "Analysis of the motion of an extrasolar planet in a binary system". Astronomy & Astrophysics. arXiv:1212.3843.
- Wittenmyer et al.; Endl, Michael; Cochran, William D.; Levison, Harold F. (2007). "Dynamical and Observational Constraints on Additional Planets in Highly Eccentric Planetary Systems". The Astronomical Journal 134 (3): 1276–1284. arXiv:0706.1962. Bibcode:2007AJ....134.1276W. doi:10.1086/520880.
- (Russian) http://www.cplire.ru/rus/ra&sr/VAK-2004.html
- Matthew Holman, Jihad Touma & Scott Tremaine (1997). "Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B". Nature 386 (6622): 254–256. Bibcode:1997Natur.386..254H. doi:10.1038/386254a0.
- Jean Schneider (2011). "Notes for star 16 Cyg B". Extrasolar Planets Encyclopaedia. Retrieved 30 September 2011.
- "16 Cygni 2?". SolStation. Retrieved 2008-06-24.
- "16 Cygni B". Extrasolar Visions. Retrieved 2008-06-24.
- "16 Cygni-B". University of Illinois at Urbana-Champaign. The Planet Project. Retrieved 2008-06-24.
- "16 Cyg B". Exoplanets. Archived from the original on 2009-05-06. Retrieved 2009-05-03.
- 16 Cygni on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images