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{{Inligtingskas ster
| naam= Kepler-20
| beeld= Kepler 20 - planet lineup.jpg
| onderskrif= Kepler-20e en 20f in vergelyking met die Aarde en Venus.
| sterrebeeld= [[Lier (sterrebeeld)|Lier]]
| bayernaam= 
| RK= 19<sup>h</sup> 10<sup>m</sup> 47,524<sup>s</sup>
| Dek= +42° 20′ 19,30″
| magnitude= 
| skynmagnitude= 12,51
| absolute magnitude= 
| ouderdom= 8,8 miljard
| massa= 0,912
| radius= 0,944
| ligsterkte= 
| spektraaltipe= G8
| soort = [[Hoofreeks]]ster
| temperatuur= 5 466
| afstand= 950
| veranderlik= 
| veelvoudig= 
| planete= 5
| name= KOI-070, KIC-6850504, 2MASSJ19104752+4220194
}}

'''Kepler-20''' is ’n [[ster]] sowat 950 [[ligjare]] van die [[Aarde]] af<ref name="Nature-20111220">{{cite journal |last=Hand |first=Eric |title=Kepler discovers first Earth-sized exoplanets |doi=10.1038/nature.2011.9688 |date=20 Desember 2011 |journal=Nature}}</ref> in die [[sterrebeeld]] [[Lier (sterrebeeld)|Lier]]. Dit het ’n stelsel van vyf bevestigde [[Planeet|planete]].<ref name="NASA-20111220">{{cite web |last=Johnson |first=Michele |title=NASA Discovers First Earth-size Planets Beyond Our Solar System |url=http://www.nasa.gov/mission_pages/kepler/news/kepler-20-system.html |publisher=Nasa |date=20 Desember 2011 |access-date=20 Desember 2011 |language=en |archive-url=https://web.archive.org/web/20200516230313/https://www.nasa.gov/mission_pages/kepler/news/kepler-20-system.html |archive-date=16 Mei 2020 |url-status=live |df=dmy-all}}</ref> Die [[Magnitude|skynbare helderheid]] van die ster is 12,51 en dit kan dus nie met die blote oog gesien word nie. Dit is effens kleiner as die [[Son]], met ’n radius van 94% en ’n massa van 91% dié van die Son. Die [[effektiewe temperatuur]] van sy fotosfeer is teen 5&nbsp;466 [[kelvin]] effens koeler as dié van die Son. Dit is egter ook ’n [[geel dwerg]] van [[spektraaltipe]] G8.<ref name=csiro />

In 2011 was dit nog nie bekend of dit ’n [[hoofreeksster]] is nie. Sy [[Metaal (astronomie)|metaalinhoud]] is waarskynlik dieselfde as die Son s’n. Dit kan ouer as die Son wees, maar die foutgrens is taamlik groot.<ref name=exoplanet />

== Planeetstelsel ==
Die span van die [[Kepler-ruimteteleskoop]] het op 20&nbsp;Desember 2011 aangekondig dat ’n vyfplaneetstelsel ontdek is met drie klein [[gasreus]]e en die eerste twee aardgrootte-planete, Kepler-20e (die eerste bekende planeet kleiner as die Aarde wat om ’n hoofreeksster wentel)<ref name="Kepler20e-20111220">{{cite web |author=Nasa |title=Kepler: A Search For Habitable Planets – Kepler-20e |url=http://kepler.nasa.gov/Mission/discoveries/kepler20e/ |date=20 Desember 2011 |publisher=Nasa |access-date=23 Desember 2011 |language=en |archive-url=https://web.archive.org/web/20170331081504/https://kepler.nasa.gov/Mission/discoveries/kepler20e/ |archive-date=31 Maart 2017 |url-status=live|df=dmy-all}}</ref> en Kepler-20f, wat om ’n Son-tipe ster wentel.<ref name="Kepler20f-20111220">{{cite web |author=Nasa |title=Kepler: A Search for Habitable Planets – Kepler-20f |url=http://kepler.nasa.gov/Mission/discoveries/kepler20f/ |date=20 Desember 2011 |publisher=Nasa |access-date=23 Desember 2011 |language=en |archive-url=https://web.archive.org/web/20170331125125/https://kepler.nasa.gov/Mission/discoveries/kepler20f/ |archive-date=31 Maart 2017 |url-status=live|df=dmy-all}}</ref> Hoewel hulle omtrent so groot soos die Aarde is, is hulle baie nader aan hul ster as die Aarde en hulle val dus nie in die bewoonbare sone nie;<ref name="Nature-20111220" /> hul verwagte oppervlaktemperatuur is 760&nbsp;°C en 427&nbsp;°C onderskeidelik. Die ander drie [[Neptunus (planeet)|Neptunus]]-tipe planete, Kepler-20b, c en d, is net so na aan die ster.<ref name="NYT-20111220">{{cite news |last=Overbye |first=Dennis |title=Two Earth-Size Planets Are Discovered |url=http://www.nytimes.com/2011/12/21/science/space/nasas-kepler-spacecraft-discovers-2-earth-size-planets.html |date=20 Desember 2011 |publisher=New York Times |access-date=21 Desember 2011 |language=en |archive-url=https://web.archive.org/web/20200516230330/https://www.nytimes.com/2011/12/21/science/space/nasas-kepler-spacecraft-discovers-2-earth-size-planets.html |archive-date=16 Mei 2020 |url-status=live |df=dmy-all}}</ref><ref name="Space-20111220">{{cite web |last=Tate |first=Karl |url=http://www.space.com/13987-earth-size-alien-planets-kepler-22e-infographic.html |title=At Last, Earth-Sized Alien Worlds (Infographic) |publisher=Space.com |date=20 Desember 2011 |access-date=21 Desember 2011 |language=en |archive-url=https://web.archive.org/web/20190609095405/https://www.space.com/13987-earth-size-alien-planets-kepler-22e-infographic.html |archive-date=9 Junie 2019 |url-status=live |df=dmy-all}}</ref>

Planete e en f se massa is onseker omdat dit te klein is om met huidige tegnologie deur middel van radiale snelheid vas te stel.<ref>http://arxiv.org/abs/1112.4550</ref>

{{Wentelkas begin
| name = Kepler-20
}}
{{Wentelkas
| exoplanet = b
| mass_earth = 8,7
| period = 3,6961219
| semimajor = 0,04537
| eccentricity = <0,32
| radius_earth = 1,91
}}
{{Wentelkas
| exoplanet = e
| mass_earth = 0,39–1,67
| period = 6,098493
| semimajor = 0,0507
| eccentricity = <0,28
| radius_earth = 0,868
}}
{{Wentelkas
| exoplanet = c
| mass_earth = 16,1
| period = 10,854092
| semimajor = 0,0930
| eccentricity = <0,40
| radius_earth = 3,07
}}
{{Wentelkas
| exoplanet = f
| mass_earth = 0,66–3,04
| period = 19,57706
| semimajor = 0,1104
| eccentricity = <0,32
| radius_earth = 1,034
}}
{{Wentelkas
| exoplanet = d
| mass_earth = <20,1
| period = 77,61184
| semimajor = 0,3453
| eccentricity = <0,60
| radius_earth = 2,75
}}
{{Wentelkas einde}}

== Verwysings ==
{{verwys
| column-count = |2|
| refs =

<ref name=exoplanet>{{citation | first1=Jean | last1=Schneider | title=Star : Kepler-20 | work=The Extrasolar Planets Encyclopaedia | publisher=CNRS/LUTH – Paris Observatory | url=http://exoplanet.eu/star.php?st=Kepler-20 | accessdate=2011-12-21 | archivedate=2012-01-19 | archiveurl=https://web.archive.org/web/20120119135819/http://exoplanet.eu/star.php?st=Kepler-20 }}</ref>

<ref name=csiro>{{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 | archivedate=2011-08-24 | archiveurl=https://www.webcitation.org/61BISbtHe?url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html }}</ref>
}}
{{Verwysings}}

== Eksterne skakels ==
* Multimedia:
** [http://www.youtube.com/watch?v=kc4PuQ6tzKo Video (01:33)] Nasa Discovers First Earth-like Exoplanet Orbiting a Sun-like Star.
{{Commons-kategorie inlyn|Kepler-20}}
* [[Lêer:Crystal txt.png|15px]] Hierdie artikel is vertaal uit die [[:en:Kepler-20|Engelse Wikipedia]]
{{Lug3|19|10|47.5|+|42|20|19.4|aansig=titel}}

{{Sterplanete}}

{{DEFAULTSORT:Kepler-020}}
[[Kategorie:Kepler-voorwerpe]]
[[Kategorie:Lier (sterrebeeld)]]
[[Kategorie:Planetêre stelsels]]
[[Kategorie:2MASS-voorwerpe]]
[[Kategorie:G-tipe hoofreekssterre]]

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