Astronomy:16 Cygni Bb
 16 Cygni Bb rendered in Celestia | |
| Discovery | |
|---|---|
| Discovered by | William D. Cochran, Artie P. Hatzes, R. Paul Butler, Geoff Marcy |
| Discovery site | United States |
| Discovery date | 22 October 1996 |
| Radial velocity | |
| Orbital characteristics | |
| 1.681 ± 0.097 AU (251,500,000 ± 14,500,000 km) | |
| Eccentricity | 0.689 ± 0.011[1] |
| Orbital period | 798.5 ± 1.0 d |
| Inclination | 45 or 135[1] |
| astron|astron|helion}} | 2,446,549.1 ± 6.6 |
| 83.4 ± 2.1[1] | |
| Semi-amplitude | 50.5 ± 1.6 |
| Star | 16 Cygni B |
| Physical characteristics | |
| Mass | 2.38 ± 0.04[1] |♃|J}}}}}} |
16 Cygni Bb or HD 186427 b is an extrasolar planet approximately 69 light-years (21 parsecs) away in the constellation of Cygnus.[2] The planet was discovered orbiting the Sun-like star 16 Cygni B, one of two solar-mass (M☉) components of the triple star system 16 Cygni in 1996.[3] It orbits its star once every 799 days and was the first eccentric Jupiter and planet in a double star system to be discovered. The planet is abundant in lithium.[4]
Discovery
In October 1996, the discovery of a planetary-mass companion to the star 16 Cygni B was announced, with a mass at least 1.68 times that of Jupiter (|♃|J}}}}}}). At the time, it had the highest orbital eccentricity of any known planet. The discovery was made by measuring the star's radial velocity.[citation needed]
As the inclination of the orbit cannot be directly measured and as no dynamic model of the system was then published, only a lower limit on the mass could then be determined.[1][5]
Orbit
Unlike the planets in the Solar System, the planet's orbit is highly elliptical, and its distance varies from 0.54 astronomical unit|AU (50 million mi; 81 million km) at periastron to 2.8 AU (260 million mi; 420 million km) at apastron.[6] This high eccentricity may have been caused by tidal interactions in the binary star system, and the planet's orbit may vary chaotically between low and high-eccentricity states over a period of tens of millions of years.[7]
Preliminary astrometric measurements in 2001 suggested the orbit of 16 Cygni Bb may be highly inclined with respect to our line of sight (at around 173°).[8] This would mean the object's mass may be around 14 |♃|J}}}}}}; the dividing line between planets and brown dwarfs is at 13 MJ. However these measurements were later proved useful only for upper limits.[9]
Physical characteristics
Because the planet has only been detected indirectly by measurements of its parent star, properties such as its radius, composition, and temperature are unknown.[citation needed]
A mathematical study in 2012 showed that a mass of about 2.4 MJ would be most stable in this system.[1] This would make the body a true planet.[citation needed]
The planet's highly eccentric orbit means the planet would experience extreme seasonal effects. Despite this, simulations suggest that an Earth-like moon, should it have formed in an orbit so close to the parent star, would be able to support liquid water at its surface for part of the year.[10]
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Plávalová, Eva; Solovaya, Nina A. (2013). "Analysis of the motion of an extrasolar planet in a binary system". The Astronomical Journal 146 (5). doi:10.1088/0004-6256/146/5/108. Bibcode: 2013AJ....146..108P.
- ↑ Cochran, William D. et al. (1997). "The Discovery of a Planetary Companion to 16 Cygni B". The Astrophysical Journal 483 (1): 457–463. doi:10.1086/304245. Bibcode: 1997ApJ...483..457C.
- ↑ "The Extrasolar Planet Encyclopaedia — 16 Cyg B b". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/16_cyg_b_b--78/.
- ↑ Deal, Morgan; Richard, Olivier; Vauclair, Sylvie (2015-12-01). "Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system" (in en). Astronomy & Astrophysics 584: A105. doi:10.1051/0004-6361/201526917. ISSN 0004-6361. Bibcode: 2015A&A...584A.105D. https://www.aanda.org/articles/aa/abs/2015/12/aa26917-15/aa26917-15.html.
- ↑ Butler, R. P.; Marcy, G. W. (1997). "The Lick Observatory Planet Search". IAU Colloq. 161: Astronomical and Biochemical Origins and the Search for Life in the Universe: 331. Bibcode: 1997abos.conf..331B.
- ↑ Butler, R. P. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. doi:10.1086/504701. Bibcode: 2006ApJ...646..505B.
- ↑ Holman, M.; Touma, J.; Tremaine, S. (1997). "Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B". Nature 386 (6622): 254–256. doi:10.1038/386254a0. Bibcode: 1997Natur.386..254H.
- ↑ Han, I.; Black, D. C.; Gatewood, G. (2001). "Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions". The Astrophysical Journal Letters 548 (1): L57–L60. doi:10.1086/318927. Bibcode: 2001ApJ...548L..57H.
- ↑ Pourbaix, D.; Arenou, F. (2001). "Screening the Hipparcos-based astrometric orbits of sub-stellar objects". Astronomy and Astrophysics 372 (3): 935–944. doi:10.1051/0004-6361:20010597. Bibcode: 2001A&A...372..935P.
- ↑ Williams, D. M.; Pollard, D. (2002). "Earth-like worlds on eccentric orbits: excursions beyond the habitable zone". International Journal of Astrobiology 1 (1): 61–69. doi:10.1017/S1473550402001064. Bibcode: 2002IJAsB...1...61W.
External links
- Jean Schneider (2011). "Notes for Planet 16 Cyg B b". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/16_cyg_b_b--78/.
- "16 Cygni 2?". http://www.solstation.com/stars2/16cygni2.htm.
- "16 Cygni-B". The Planet Project. http://www.astro.uiuc.edu/~kaler/sow/16cyg.html.
- "16 Cyg B". http://media4.obspm.fr/exoplanets/base/etoile.php?nom=16+Cyg+B.
Coordinates: 
19h 41m 51.9720s, +50° 31′ 03.083″
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