Editing Exoplanet (section)

==Planet-hosting stars==
{{Main|Planet-hosting star}}
[[File:Morgan-Keenan spectral classification.svg|thumb|upright=1.2|alt=The Morgan-Keenan spectral classification system, showing size-and-color comparisons of M, K, G, F, A, B, and O stars|The Morgan-Keenan spectral classification]]
[[File:OGLE-2007-BLG-349.jpg|thumb|upright=1|Artist's impression of exoplanet orbiting two stars.<ref>{{cite web|title=Artist's impression of exoplanet orbiting two stars|url=http://www.spacetelescope.org/images/heic1619a/|website=www.spacetelescope.org|access-date=24 September 2016}}</ref>]]
There is at least one planet on average per star.<ref name="Nature-20120111" /> About 1 in 5 [[Solar analog|Sun-like stars]]<ref group=lower-alpha name=footnoteA /> have an "Earth-sized"<ref group=lower-alpha name=footnoteB /> planet in the [[habitable zone]].<ref name="earthsunhzprev">{{cite journal|last1=Petigura |first1=E. A.|last2=Howard |first2=A. W.|last3=Marcy |first3=G. W.|date=2013|title=Prevalence of Earth-size planets orbiting Sun-like stars|journal=[[Proceedings of the National Academy of Sciences]]| volume= 110| issue= 48| pages=19273–19278|arxiv= 1311.6806| bibcode= 2013PNAS..11019273P| doi=10.1073/pnas.1319909110 | pmid=24191033 | pmc=3845182|doi-access=free}}</ref>

Most known exoplanets orbit stars roughly similar to the [[Sun]], i.e. [[main sequence|main-sequence stars]] of [[stellar classification|spectral categories]] F, G, or K. Lower-mass stars ([[red dwarf]]s, of [[stellar classification|spectral category]] M) are less likely to have planets massive enough to be detected by the [[radial-velocity method]].<ref name="cumming08">{{Cite journal|year=2008|title=The Keck Planet Search: Detectability and the Minimum Mass and Orbital Period Distribution of Extrasolar Planets|journal=Publications of the Astronomical Society of the Pacific|volume=120| issue=867|pages=531–554| arxiv=0803.3357|doi=10.1086/588487| bibcode=2008PASP..120..531C|author-link3=Geoffrey Marcy|author-link4=Steven S. Vogt|author-link6=Debra Fischer |last1=Cumming|first1=Andrew|last2=Butler|first2=R. Paul|last3=Marcy|first3=Geoffrey W.|last4=Vogt|first4=Steven S.|last5=Wright|first5=Jason T.|last6=Fischer|first6=Debra A.|s2cid=10979195}}</ref><ref name="bonfils05">{{Cite journal |doi=10.1051/0004-6361:200500193 |title=The HARPS search for southern extra-solar planets VI: A Neptune-mass planet around the nearby M dwarf Gl 581 |journal=Astronomy and Astrophysics |volume=443 |issue=3 |pages=L15–L18 |year=2005 |last1=Bonfils |first1=Xavier |last2=Forveille |first2=Thierry |last3=Delfosse |first3=Xavier |last4=Udry |first4=Stéphane |last5=Mayor |first5=Michel |last6=Perrier |first6=Christian |last7=Bouchy |first7=François |last8=Pepe |first8=Francesco |last9=Queloz |first9=Didier |last10=Bertaux |first10=Jean-Loup |bibcode=2005A&A...443L..15B |arxiv=astro-ph/0509211 |s2cid=59569803 }}</ref> Despite this, several tens of planets around red dwarfs have been discovered by the [[Kepler space telescope]], which uses the [[transit method]] to detect smaller planets.

Using data from [[Kepler space telescope|Kepler]], a correlation has been found between the [[metallicity]] of a star and the probability that the star hosts a giant planet, similar to the size of [[Jupiter]]. Stars with higher metallicity are more likely to have planets, especially giant planets, than stars with lower metallicity.<ref>{{Cite journal | doi = 10.1088/0004-6256/149/1/14| title = Revealing a Universal Planet–Metallicity Correlation for Planets of Different Solar-Type Stars| journal = The Astronomical Journal| volume = 149| issue = 1| page = 14| year = 2014| last1 = Wang | first1 = J. | last2 = Fischer | first2 = D. A. | bibcode = 2015AJ....149...14W|arxiv = 1310.7830 | s2cid = 118415186}}</ref>

Some planets orbit one member of a [[binary star]] system,<ref>{{Cite web|title=Science work|url=https://www.univie.ac.at/adg/schwarz/multiple.html|access-date=2022-01-17|website=www.univie.ac.at}}</ref> and several [[circumbinary planet]]s have been discovered which orbit both members of a binary star. A few planets in [[triple star]] systems are known<ref>{{Cite web|title=STAR-DATA|url=https://www.univie.ac.at/adg/schwarz/multi.html|access-date=2022-01-17|website=www.univie.ac.at}}</ref> and one in the quadruple system [[PH1b|Kepler-64]].