Editing Exoplanet (section)

=== Confirmed discoveries ===
{{Main|Discoveries of exoplanets}}
{{See also|List of exoplanet firsts}}
[[File:The Star AB Pictoris and its Companion - Phot-14d-05-normal.jpg|thumb|300px|[[Coronagraph]]ic image of [[AB Pictoris]] showing a companion (bottom left), which is either a brown dwarf or a massive planet. The data were obtained on 16 March 2003 with [[List of instruments at the Very Large Telescope|NACO]] on the [[Very Large Telescope|VLT]], using a 1.4 arcsec occulting mask on top of AB Pictoris.]]
{{multiple image
| align             = right
| direction         = vertical
| width             = 300
| image1            = 444226main exoplanet20100414-a-full.jpg
| alt1              = False-color, star-subtracted, direct image using a vortex coronagraph of 3 exoplanets around star HR8799
| caption1          = The three known planets of the star [[HR 8799]], as imaged by the [[Hale Telescope]]. The light from the central star was blanked out by a [[vector vortex coronagraph]].
| image2            = Brown dwarf 2M J044144 and planet.jpg
| alt2              = Hubble image of brown dwarf 2MASS J044144 and its 5–10 Jupiter-mass companion, before and after star-subtraction
| caption2          = [[2MASS J044144]] is a [[brown dwarf]] with a companion about 5–10 times the mass of Jupiter. It is not clear whether this companion object is a [[sub-brown dwarf]] or a planet.
}}

As of {{Extrasolar planet counts|asof}}, a total of {{Extrasolar planet counts|planet_count|source=NEA}} confirmed exoplanets are listed in the [[NASA Exoplanet Archive]], including a few that were confirmations of controversial claims from the late 1980s.{{Extrasolar planet counts|ref}} The first published discovery to receive subsequent confirmation was made in 1988 by the Canadian astronomers Bruce Campbell, G. A. H. Walker, and Stephenson Yang of the [[University of Victoria]] and the [[University of British Columbia]].<ref name="Campbell">{{Cite journal | last1 = Campbell | first1 = B. | last2 = Walker | first2 = G. A. H. | last3 = Yang | first3 = S. | title = A search for substellar companions to solar-type stars | doi = 10.1086/166608 | journal = The Astrophysical Journal | volume = 331 | page = 902 | year = 1988 | bibcode=1988ApJ...331..902C| doi-access = free }}</ref> Although they were cautious about claiming a planetary detection, their radial-velocity observations suggested that a planet orbits the star [[Gamma Cephei]]. Partly because the observations were at the very limits of instrumental capabilities at the time, astronomers remained skeptical for several years about this and other similar observations. It was thought some of the apparent planets might instead have been [[brown dwarf]]s, objects intermediate in mass between planets and stars. In 1990, additional observations were published that supported the existence of the planet orbiting Gamma Cephei,<ref>{{Cite journal|last1=Lawton |first1=A. T.|last2=Wright |first2=P.|date=1989|title=A planetary system for Gamma Cephei?|journal=[[Journal of the British Interplanetary Society]]|volume=42|pages=335–336|bibcode=1989JBIS...42..335L}}</ref> but subsequent work in 1992 again raised serious doubts.<ref name="Walker">{{Cite journal|last1=Walker |first1=G. A. H|date=1992|title=Gamma Cephei&nbsp;– Rotation or planetary companion?|journal=[[Astrophysical Journal Letters]]|volume=396|issue=2|pages=L91–L94|doi=10.1086/186524|bibcode=1992ApJ...396L..91W|last2=Bohlender |first2=D. A.|last3=Walker |first3=A. R.|last4=Irwin |first4=A. W.|last5=Yang |first5=S. L. S.|last6=Larson |first6=A.|doi-access=free}}</ref> Finally, in 2003, improved techniques allowed the planet's existence to be confirmed.<ref>{{Cite journal|last1=Hatzes |first1=A. P.|last2=Cochran |first2=William D.|title=A Planetary Companion to Gamma Cephei A|journal=[[Astrophysical Journal]]|date=2003|volume=599|issue=2|pages=1383–1394|doi =10.1086/379281|bibcode=2003ApJ...599.1383H|arxiv = astro-ph/0305110|last3=Endl|first3=Michael|last4=McArthur|first4=Barbara|last5=Paulson|first5=Diane B.|last6=Walker|first6=Gordon A. H.|last7=Campbell|first7=Bruce|last8=Yang|first8=Stephenson|s2cid=11506537}}</ref>

On 9 January 1992, radio astronomers [[Aleksander Wolszczan]] and [[Dale Frail]] announced the discovery of two planets orbiting the [[millisecond pulsar]] [[PSR B1257+12|PSR 1257+12]] based on the variability of timing of the pulses.<ref name="Wolszczan">{{Cite journal | last1 = Wolszczan | first1 = A. |bibcode=1992Natur.355..145W| last2 = Frail | first2 = D. A. | doi = 10.1038/355145a0 | title = A planetary system around the millisecond pulsar PSR1257 + 12 | journal = Nature | volume = 355 | issue = 6356 | pages = 145–147 | year = 1992 | s2cid = 4260368 }}</ref> This discovery was confirmed, and is generally considered to be the first definitive detection of exoplanets. Follow-up observations solidified these results, and confirmation of a third planet in 1994 revived the topic in the popular press.<ref>{{cite news | url=http://tech.mit.edu/V114/N22/psr.22w.html | title=Scientists Uncover Evidence of New Planets Orbiting Star | newspaper=Los Angeles Times via [[The Tech (newspaper)|The Tech Online]] | first=Robert | last=Holtz | date=22 April 1994 | access-date=20 April 2012 | archive-date=17 May 2013 | archive-url=https://web.archive.org/web/20130517225034/http://tech.mit.edu/V114/N22/psr.22w.html | url-status=dead }}</ref> These pulsar planets are thought to have formed from the unusual remnants of the [[supernova]] that produced the pulsar, in a second round of planet formation, or else to be the [[Chthonian planet|remaining rocky cores]] of [[gas giant]]s that somehow survived the supernova and then decayed into their current orbits. As pulsars are aggressive stars, it was considered unlikely at the time that a planet could form in their orbit.<ref>{{cite book |last= Rodriguez Baquero|first= Oscar Augusto|date= 2017|title= La presencia humana más allá del sistema solar|trans-title= Human presence beyond the solar system|url= |language= Spanish|page=29|location= |publisher= RBA|isbn=978-84-473-9090-8}}</ref>

In the early 1990s, a group of astronomers led by [[Donald Backer]], who were studying what they thought was a binary pulsar ([[PSR B1620−26 b]]), determined that a third object was needed to explain the observed [[Doppler shift]]s. Within a few years, the gravitational effects of the planet on the orbit of the pulsar and [[white dwarf]] had been measured, giving an estimate of the mass of the third object that was too small to be a star. The conclusion that the third object was a planet was announced by [[Stephen Thorsett]] and his collaborators in 1993.<ref name="STScI">{{cite web | title=Oldest Known Planet Identified | work=[[HubbleSite]] | url=http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/19/ | access-date=2006-05-07}}</ref>

On 6 October 1995, [[Michel Mayor]] and [[Didier Queloz]] of the [[University of Geneva]] announced the first definitive detection of [[51 Pegasi b|an exoplanet]] orbiting a [[main sequence|main-sequence]] star, nearby [[G-type star]] [[51 Pegasi]].<ref name="Wenz"/><ref name="Mayor">{{Cite journal | doi = 10.1038/378355a0| title = A Jupiter-mass companion to a solar-type star| journal = Nature| volume = 378| issue = 6555| pages = 355–359| year = 1995| last1 = Mayor | first1 = M. | last2 = Queloz | first2 = D. | bibcode = 1995Natur.378..355M| s2cid = 4339201}}</ref><ref name=gibn>{{cite journal|last1=Gibney|first1=Elizabeth|title=In search of sister earths|journal=Nature|date=18 December 2013|volume=504|issue=7480|pages=357–365|doi=10.1038/504357a|pmid=24352276|bibcode = 2013Natur.504..357. |doi-access=free}}</ref> This discovery, made at the [[Observatoire de Haute-Provence]], ushered in the modern era of exoplanetary discovery, and was recognized by a share of the 2019 [[Nobel Prize in Physics]]. Technological advances, most notably in high-resolution [[spectroscopy]], led to the rapid detection of many new exoplanets: astronomers could detect exoplanets indirectly by measuring their [[gravity|gravitational]] influence on the motion of their host stars. More extrasolar planets were later detected by observing the variation in a star's apparent luminosity as an orbiting planet transited in front of it.<ref name="Wenz"/>

Initially, the most known exoplanets were massive planets that orbited very close to their parent stars. Astronomers were surprised by these "[[hot Jupiter]]s", because theories of [[Nebular hypothesis#Formation of planets|planetary formation]] had indicated that giant planets should only form at large distances from stars. But eventually more planets of other sorts were found, and it is now clear that hot Jupiters make up the minority of exoplanets.<ref name="Wenz">{{cite journal |last1=Wenz |first1=John |title=Lessons from scorching hot weirdo-planets |journal=Knowable Magazine |publisher= Annual Reviews |date=10 October 2019 |doi=10.1146/knowable-101019-2|doi-access=free |url=https://knowablemagazine.org/article/physical-world/2019/hot-jupiter-formation-theories |access-date=4 April 2022 |language=en}}</ref> In 1999, [[Upsilon Andromedae]] became the first main-sequence star known to have multiple planets.<ref name="Lissauer_multiple99">{{Cite journal | doi = 10.1038/19409| year = 1999| last1 = Lissauer | first1 = J. J. | title = Three planets for Upsilon Andromedae| journal = Nature| volume = 398| issue = 6729| page = 659| bibcode = 1999Natur.398..659L| s2cid = 204992574| doi-access = free}}</ref> [[Kepler-16]] contains the first discovered planet that orbits a binary main-sequence star system.<ref name=Doyle>{{Cite journal | doi = 10.1126/science.1210923| pmid = 21921192| title = Kepler-16: A Transiting Circumbinary Planet| journal = Science| volume = 333| issue = 6049| pages = 1602–1606| year = 2011| last1 = Doyle | first1 = L. R.| last2 = Carter | first2 = J. A.| last3 = Fabrycky | first3 = D. C.| last4 = Slawson | first4 = R. W.| last5 = Howell | first5 = S. B.| last6 = Winn | first6 = J. N.| last7 = Orosz | first7 = J. A.| last8 = Prša | first8 = A.| last9 = Welsh | first9 = W. F.| last10 = Quinn | first10 = S. N.| last11 = Latham | first11 = D.| last12 = Torres | first12 = G.| last13 = Buchhave | first13 = L. A.| last14 = Marcy | first14 = G. W.| last15 = Fortney | first15 = J. J.| last16 = Shporer | first16 = A.| last17 = Ford | first17 = E. B.| last18 = Lissauer | first18 = J. J.| last19 = Ragozzine | first19 = D.| last20 = Rucker | first20 = M.| last21 = Batalha | first21 = N.| last22 = Jenkins | first22 = J. M.| last23 = Borucki | first23 = W. J.| last24 = Koch | first24 = D.| last25 = Middour | first25 = C. K.| last26 = Hall | first26 = J. R.| last27 = McCauliff | first27 = S.| last28 = Fanelli | first28 = M. N.| last29 = Quintana | first29 = E. V.| last30 = Holman | first30 = M. J.| display-authors = etal| bibcode = 2011Sci...333.1602D|arxiv = 1109.3432 | s2cid = 206536332}}</ref>

On 26 February 2014, NASA announced the discovery of 715 newly verified exoplanets around 305 stars by the [[Kepler (spacecraft)|''Kepler'' Space Telescope]]. These exoplanets were checked using a statistical technique called "verification by multiplicity".<ref name="kepler1700">{{cite web |last1=Johnson |first1=Michele |last2=Harrington |first2=J.D. |title=NASA's Kepler Mission Announces a Planet Bonanza, 715 New Worlds |url=http://www.nasa.gov/ames/kepler/nasas-kepler-mission-announces-a-planet-bonanza/ |date=26 February 2014 |work=[[NASA]] |access-date=26 February 2014 |archive-date=26 February 2014 |archive-url=https://web.archive.org/web/20140226202703/http://www.nasa.gov/ames/kepler/nasas-kepler-mission-announces-a-planet-bonanza/ |url-status=dead }}</ref><ref name="space.com">{{cite web|last=Wall|first=Mike|title=Population of Known Alien Planets Nearly Doubles as NASA Discovers 715 New Worlds|url=http://www.space.com/24824-alien-planets-population-doubles-nasa-kepler.html|date=26 February 2014|access-date=27 February 2014|publisher=space.com}}</ref><ref name="bbcnews">{{cite news |author=Amos |first=Jonathan |date=26 February 2014 |title=Kepler telescope bags huge haul of planets |url=https://www.bbc.co.uk/news/science-environment-26362433 |access-date=27 February 2014 |work=BBC News}}</ref> Before these results, most confirmed planets were gas giants comparable in size to Jupiter or larger because they were more easily detected, but the ''Kepler'' planets are mostly between the size of Neptune and the size of Earth.<ref name="kepler1700" />

On 23 July 2015, NASA announced [[Kepler-452b]], a near-Earth-size planet orbiting the habitable zone of a G2-type star.<ref name="NASA-20150723">{{cite web |last1=Johnson |first1=Michelle |last2=Chou |first2=Felicia |title=NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth |url=http://www.nasa.gov/press-release/nasa-kepler-mission-discovers-bigger-older-cousin-to-earth |date=23 July 2015 |work=[[NASA]]}}</ref>

On 6 September 2018, NASA discovered an exoplanet about 145 light years away from Earth in the constellation Virgo.<ref name="Oddball">{{Cite news |last=NASA |title=Discovery alert! Oddball planet could surrender its secrets |url=https://exoplanets.nasa.gov/news/1521/discovery-alert-oddball-planet-could-surrender-its-secrets/ |access-date=28 November 2018 |work=Exoplanet Exploration: Planets Beyond our Solar System}}</ref> This exoplanet, Wolf 503b, is twice the size of Earth and was discovered orbiting a type of star known as an "Orange Dwarf". Wolf 503b completes one orbit in as few as six days because it is very close to the star. Wolf 503b is the only exoplanet that large that can be found near the so-called [[small planet radius gap]]. The gap, sometimes called the Fulton gap,<ref name="Oddball"/><ref>{{Cite journal |last1=Fulton |first1=Benjamin J. |last2=Petigura |first2=Erik A. |last3=Howard |first3=Andrew W. |last4=Isaacson |first4=Howard |last5=Marcy |first5=Geoffrey W. |last6=Cargile |first6=Phillip A. |last7=Hebb |first7=Leslie |last8=Weiss |first8=Lauren M. |last9=Johnson |first9=John Asher |last10=Morton |first10=Timothy D. |last11=Sinukoff |first11=Evan |last12=Crossfield |first12=Ian J. M. |last13=Hirsch |first13=Lea A. |date=2017-09-01 |title=The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets* |journal=The Astronomical Journal |volume=154 |issue=3 |pages=109 |doi=10.3847/1538-3881/aa80eb |doi-access=free |arxiv=1703.10375 |bibcode=2017AJ....154..109F |issn=0004-6256}}</ref> is the observation that it is unusual to find exoplanets with sizes between 1.5 and 2 times the radius of the Earth.<ref>{{Cite web |title=Radius Gap |url=https://sites.astro.caltech.edu/~fdai/radius_gap.html |access-date=2024-04-03 |website=sites.astro.caltech.edu}}</ref>

In January 2020, scientists announced the discovery of [[TOI 700 d]], the first Earth-sized planet in the habitable zone detected by TESS.<ref>{{Cite web|url=https://www.midilibre.fr/2020/01/07/toi-700d-une-planete-de-la-taille-de-la-terre-decouverte-dans-une-zone-habitable,8645004.php|title=[VIDEO] TOI 700d : une planète de la taille de la Terre découverte dans une "zone habitable"|website=midilibre.fr|language=fr|access-date=2020-04-17}}</ref>