16 Cygni Bb
{{Short description|Extrasolar planet}}
{{good article}}
{{Infobox planet
| name = 16 Cygni Bb
| symbol =
| image = File:16 Cygni B b.png
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| caption = 16 Cygni Bb rendered in Celestia
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| discoverer = William D. Cochran, Artie P. Hatzes, R. Paul Butler, Geoff Marcy
| discovery_site = United States
| discovered = 22 October 1996
| discovery_method = Radial velocity
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| minorplanet = no
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| apsis = astron
| aphelion =
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| semimajor = {{convert|1.681 ± 0.097|AU|km|abbr=on}}
| mean_orbit_radius =
| eccentricity = 0.689 ± 0.011
| period = 798.5 ± 1.0 d
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| long_periastron =
| time_periastron = 2,446,549.1 ± 6.6
| semi-amplitude = 50.5 ± 1.6
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| star = 16 Cygni B
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| mass = 2.38 ± 0.04 {{Jupiter mass|link=y}}
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16 Cygni Bb or HD 186427 b is an extrasolar planet approximately {{Convert|69|ly|pc|abbr=off|lk=on}} away in the constellation of Cygnus. The planet was discovered orbiting the Sun-like star 16 Cygni B, one of two solar-mass ({{Solar mass|link=y}}) components of the triple star system 16 Cygni in 1996.{{Cite web|title=The Extrasolar Planet Encyclopaedia — 16 Cyg B b|url=https://exoplanet.eu/catalog/16_cyg_b_b--78/|work=Extrasolar Planets Encyclopaedia|access-date=2020-08-15}} 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.{{Cite journal|last1=Deal|first1=Morgan|last2=Richard|first2=Olivier|last3=Vauclair|first3=Sylvie |author-link3=Sylvie Vauclair|date=2015-12-01|title=Accretion of planetary matter and the lithium problem in the 16 Cygni stellar system|url=https://www.aanda.org/articles/aa/abs/2015/12/aa26917-15/aa26917-15.html|journal=Astronomy & Astrophysics|language=en|volume=584|pages=A105|doi=10.1051/0004-6361/201526917|arxiv=1509.06958 |bibcode=2015A&A...584A.105D |issn=0004-6361|doi-access=free}}
Discovery
On the 22nd of 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 ({{Jupiter mass|link=y}}). At the time, it had the highest orbital eccentricity of any known planet. The discovery was made by measuring the star's radial velocity.
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.{{cite journal | bibcode=1997abos.conf..331B | first1=R. P. | last1=Butler | title=The Lick Observatory Planet Search | last2=Marcy | first2=G. W. | journal=IAU Colloq. 161: Astronomical and Biochemical Origins and the Search for Life in the Universe | year=1997| page=331}}
Orbit
Unlike the planets in the Solar System, the planet's orbit is highly elliptical, and its distance varies from {{Convert|0.54|AU|e6mi e6km|abbr=unit|lk=on}} at periastron to {{Convert|2.8|AU|e6mi e6km|abbr=unit|lk=off}} at apastron.{{cite journal
|last=Butler |first=R. P.
|year=2006
|title=Catalog of Nearby Exoplanets
|journal=The Astrophysical Journal
|volume=646 |issue=1 |pages=505–522
|arxiv=astro-ph/0607493
|bibcode=2006ApJ...646..505B
|doi=10.1086/504701
|s2cid=119067572
|display-authors=etal}} 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.{{cite journal
|last1=Holman |first1=M.
|last2=Touma |first2=J.
|last3=Tremaine |first3=S.
|year=1997
|title=Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B
|journal=Nature
|volume=386|issue=6622|pages=254–256
|bibcode=1997Natur.386..254H
|doi=10.1038/386254a0
|s2cid=4312547
}}
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°).{{cite journal
|last1=Han |first1=I.
|last2=Black |first2=D. C.
|last3=Gatewood |first3=G.
|year=2001
|title=Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions
|journal=The Astrophysical Journal Letters
|volume=548 |issue=1 |pages=L57–L60
|bibcode=2001ApJ...548L..57H
|doi=10.1086/318927
|doi-access=
}} This would mean the object's mass may be around {{Jupiter mass|14|link=y}}; the dividing line between planets and brown dwarfs is at {{Jupiter mass|13}}. However these measurements were later proved useful only for upper limits.{{cite journal
|last1=Pourbaix |first=D.
|last2=Arenou |first2=F.
|year=2001
|title=Screening the Hipparcos-based astrometric orbits of sub-stellar objects
|journal=Astronomy and Astrophysics
|volume=372 |issue=3 |pages=935–944
|arxiv=astro-ph/0104412
|bibcode=2001A&A...372..935P
|doi=10.1051/0004-6361:20010597
|s2cid=378792
}}
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|date=November 2023}}
A mathematical study in 2012 showed that a mass of about {{Jupiter mass|2.4}} would be most stable in this system. This would make the body a true planet.{{Citation needed|date=November 2023}}
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.{{cite journal
|last1=Williams |first1=D. M.
|last2=Pollard |first2=D.
|year=2002
|title=Earth-like worlds on eccentric orbits: excursions beyond the habitable zone
|journal=International Journal of Astrobiology
|volume=1 |issue=1 |pages=61–69
|bibcode=2002IJAsB...1...61W
|doi=10.1017/S1473550402001064
|s2cid=37593615
}}
See also
References
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External links
- {{cite web |url=https://exoplanet.eu/catalog/16_cyg_b_b--78/ |title=Notes for Planet 16 Cyg B b |author=Jean Schneider |year=2011 |work=Extrasolar Planets Encyclopaedia |access-date=30 September 2011}}
- {{cite web |url=http://www.solstation.com/stars2/16cygni2.htm |title=16 Cygni 2? |access-date=2008-06-24 |website=SolStation}}
- {{cite web |url=http://www.astro.uiuc.edu/~kaler/sow/16cyg.html |title=16 Cygni-B |access-date=2008-06-24 |website=University of Illinois at Urbana–Champaign |publisher=The Planet Project |url-status=dead |archive-url=https://web.archive.org/web/20080518004546/http://www.astro.uiuc.edu/~kaler/sow/16cyg.html |archive-date=2008-05-18 }}
- {{cite web |url=http://media4.obspm.fr/exoplanets/base/etoile.php?nom=16+Cyg+B |title=16 Cyg B |website=Exoplanets |access-date=2009-05-03 |archive-url=https://web.archive.org/web/20091125002817/http://media4.obspm.fr/exoplanets/base/etoile.php?nom=16+Cyg+B |archive-date=2009-11-25 |url-status=dead }}
{{Sky|19|41|51.9720|+|50|31|03.083|70.5}}
Category:Cygnus (constellation)
Category:Exoplanets discovered in 1996