Editing Exoplanet (section)

=== Indirect methods ===
* [[Transit method]]
: [[File:Planet reflex sm.gif|alt=|thumb|A planet is able to gravitationally pull its host star]][[File:Dopspec-inline.gif|thumb|alt=Edge-on animation of a star-planet system, showing the geometry considered for the transit method of exoplanet detection|When the star is behind a planet, its brightness will seem to dim]]If a planet crosses (or [[Astronomical transit|transits]]) in front of its parent star's disk, then the observed brightness of the star drops by a small amount. The amount by which the star dims depends on its size and on the size of the planet, among other factors. Because the transit method requires that the planet's  orbit intersect a line-of-sight between the host star and Earth, the probability that an exoplanet in a randomly oriented orbit will be observed to transit the star is somewhat small. The [[Kepler (spacecraft)|Kepler telescope]] used this method.
[[File:Exoplanet detections per year.png|thumb|upright=1.4|Exoplanet detections per year as of September 2024<ref>{{cite web |title=Pre-generated Exoplanet Plots |url=https://exoplanetarchive.ipac.caltech.edu/exoplanetplots/ |website=exoplanetarchive.ipac.caltech.edu |publisher=[[NASA Exoplanet Archive]] |access-date=10 July 2023}}</ref>]]

* [[Methods of detecting exoplanets#Radial velocity|Radial velocity or Doppler method]]
:As a planet orbits a star, the star also moves in its own small orbit around the system's center of mass. Variations in the star's radial velocity—that is, the speed with which it moves towards or away from Earth—can be detected from displacements in the star's [[spectral line]]s due to the [[Doppler effect]]. Extremely small radial-velocity variations can be observed, of 1&nbsp;m/s or even somewhat less.<ref name="Pepe_HarpsEarthlike11">{{Cite journal | doi = 10.1051/0004-6361/201117055| title = The HARPS search for Earth-like planets in the habitable zone| journal = Astronomy & Astrophysics| volume = 534| pages = A58| year = 2011| last1 = Pepe | first1 = F.| last2 = Lovis | first2 = C.| last3 = Ségransan | first3 = D.| last4 = Benz | first4 = W.| last5 = Bouchy | first5 = F.| last6 = Dumusque | first6 = X.| last7 = Mayor | first7 = M.| last8 = Queloz | first8 = D.| last9 = Santos | first9 = N. C.| last10 = Udry | first10 = S.| bibcode = 2011A&A...534A..58P|arxiv = 1108.3447 | s2cid = 15088852}}</ref> 
* [[Methods of detecting exoplanets#Transit timing|Transit timing variation]] (TTV) 
:When multiple planets are present, each one slightly perturbs the others' orbits. Small variations in the times of transit for one planet can thus indicate the presence of another planet, which itself may or may not transit. For example, variations in the transits of the planet [[Kepler-19b]] suggest the existence of a second planet in the system, the non-transiting [[Kepler-19c]].<ref name=ttv1>[http://www.scientificcomputing.com/news-DS-Planet-Hunting-Finding-Earth-like-Planets-071910.aspx Planet Hunting: Finding Earth-like Planets] {{Webarchive|url=https://web.archive.org/web/20100728093120/http://www.scientificcomputing.com/news-DS-Planet-Hunting-Finding-Earth-like-Planets-071910.aspx |date=2010-07-28 }}. Scientific Computing. 19 July 2010</ref><ref>{{Cite journal | doi = 10.1088/0004-637X/743/2/200|arxiv=1109.1561|bibcode=2011ApJ...743..200B| title = The Kepler-19 System: A Transiting 2.2 R<sub>⊕</sub> Planet and a Second Planet Detected Via Transit Timing Variations| journal = The Astrophysical Journal| volume = 743| issue = 2| page = 200| year = 2011| last1 = Ballard | first1 = S. | last2 = Fabrycky | first2 = D. | last3 = Fressin | first3 = F. | last4 = Charbonneau | first4 = D. | last5 = Desert | first5 = J. M. | last6 = Torres | first6 = G. | last7 = Marcy | first7 = G. | last8 = Burke | first8 = C. J. | last9 = Isaacson | first9 = H. | last10 = Henze | first10 = C. | last11 = Steffen | first11 = J. H. | last12 = Ciardi | first12 = D. R. | last13 = Howell | first13 = S. B. | last14 = Cochran | first14 = W. D. | last15 = Endl | first15 = M. | last16 = Bryson | first16 = S. T. | last17 = Rowe | first17 = J. F. | last18 = Holman | first18 = M. J. | last19 = Lissauer | first19 = J. J. | last20 = Jenkins | first20 = J. M. | last21 = Still | first21 = M. | last22 = Ford | first22 = E. B. | last23 = Christiansen | first23 = J. L. | last24 = Middour | first24 = C. K. | last25 = Haas | first25 = M. R. | last26 = Li | first26 = J. | last27 = Hall | first27 = J. R. | last28 = McCauliff | first28 = S. | last29 = Batalha | first29 = N. M. | last30 = Koch | first30 = D. G. |s2cid=42698813| display-authors = etal}}</ref> 
* [[Methods of detecting extrasolar planets#Transit duration variation|Transit duration variation (TDV)]]
[[File:201008-2a PlanetOrbits 16x9- Transit timing of 1-planet vs 2-planet systems.ogv|thumb|300px|alt=Animation showing the difference between planet transit timing of one-planet and two-planet systems|Animation showing difference between planet transit timing of one-planet and two-planet systems]]
:When a planet orbits multiple stars or if the planet has moons, its transit time can significantly vary per transit. Although no new planets or moons have been discovered with this method, it is used to successfully confirm many transiting circumbinary planets.<ref>{{cite journal |last1=Pál |first1=A. |last2=Kocsis |first2=B. |title=Periastron Precession Measurements in Transiting Extrasolar Planetary Systems at the Level of General Relativity |date=2008 |doi=10.1111/j.1365-2966.2008.13512.x |journal=Monthly Notices of the Royal Astronomical Society |volume=389 |issue=1 |pages=191–198 |doi-access=free |arxiv=0806.0629|bibcode = 2008MNRAS.389..191P |s2cid=15282437 }}</ref>
* [[Methods of detecting extrasolar planets#Gravitational microlensing|Gravitational microlensing]]
:Microlensing occurs when the gravitational field of a star acts like a lens, magnifying the light of a distant background star. Planets orbiting the lensing star can cause detectable anomalies in magnification as it varies over time. Unlike most other methods which have a detection bias towards planets with small (or for resolved imaging, large) orbits, the microlensing method is most sensitive to detecting planets around 1–10&nbsp;[[astronomical unit|AU]] away from Sun-like stars.
* [[Methods of detecting extrasolar planets#Astrometry|Astrometry]]
:Astrometry consists of precisely measuring a star's position in the sky and observing the changes in that position over time. The motion of a star due to the gravitational influence of a planet may be observable. Because the motion is so small, however, this method was not very productive until the 2020s. It has produced only a few confirmed discoveries,<ref name="Curiel2022">{{cite journal |arxiv=2208.14553 |last1=Curiel |first1=Salvador |last2=Ortiz-León |first2=Gisela N. |last3=Mioduszewski |first3=Amy J. |last4=Sanchez-Bermudez |first4=Joel |date=September 2022 |title=3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion |journal=[[The Astronomical Journal]] |volume=164 |issue=3 |page=93 |doi=10.3847/1538-3881/ac7c66 |bibcode=2022AJ....164...93C|s2cid=251953478 |doi-access=free }}</ref><ref name="Sozzetti2023">{{cite journal |last1=Sozzetti |first1=A. |last2=Pinamonti |first2=M. |display-authors=etal |date=September 2023 |title=The GAPS Programme at TNG. XLVII. A conundrum resolved: HIP 66074b/Gaia-3b characterised as a massive giant planet on a quasi-face-on and extremely elongated orbit |journal=[[Astronomy & Astrophysics]] |volume=677 |issue= |pages=L15 |doi=10.1051/0004-6361/202347329 |doi-access=free |bibcode=2023A&A...677L..15S|hdl=2108/347124 |hdl-access=free }}</ref> though it has been successfully used to investigate the properties of planets found in other ways.
* [[Pulsar timing]]
:A [[pulsar]], a small, dense remnant of a star that has exploded as a [[supernova]], emits radio waves regularly as it rotates. If planets orbit the pulsar, the motion of the pulsar around the system's center of mass alters the pulsar's distance to Earth over time. As a result, the radio pulses from the pulsar arrive on Earth at a later or earlier time. This light travel delay due to the pulsar being physically closer or farther from Earth is known as a Roemer time delay.<ref>{{Cite journal |last=Damour |first=Thibault |date=1992 |title=Strong-field tests of relativistic gravity and binary pulsars |url=https://journals.aps.org/prd/abstract/10.1103/PhysRevD.45.1840 |journal=Physical Review D |volume=45 |issue=6 |pages=1840–1868 |doi=10.1103/PhysRevD.45.1840|pmid=10014561 |bibcode=1992PhRvD..45.1840D }}</ref> [[PSR B1257+12|The first confirmed discovery of an extrasolar planet]] was made using this method. But as of 2011, it has not been very productive; five planets have been detected in this way, around three different pulsars.
* [[Methods of detecting extrasolar planets#Variable star timing|Variable star timing (pulsation frequency)]]
:Like pulsars, there are some other types of stars which exhibit periodic activity. Deviations from periodicity can sometimes be caused by a planet orbiting it. As of 2013, a few planets have been discovered with this method.<ref>{{Cite journal | doi = 10.1038/nature06143|pmid=17851517|bibcode = 2007Natur.449..189S |url=http://www.physics.udel.edu/gp/darc/wet/pubs/silvotti.pdf| title = A giant planet orbiting the 'extreme horizontal branch' star V 391 Pegasi| journal = Nature| volume = 449| issue = 7159| pages = 189–191| year = 2007| last1 = Silvotti | first1 = R.| last2 = Schuh | first2 = S.| last3 = Janulis | first3 = R.| last4 = Solheim | first4 = J. -E. | last5 = Bernabei | first5 = S.| last6 = Østensen | first6 = R.| last7 = Oswalt | first7 = T. D.| last8 = Bruni | first8 = I.| last9 = Gualandi | first9 = R.| last10 = Bonanno | first10 = A.| last11 = Vauclair | first11 = G.| last12 = Reed | first12 = M.| last13 = Chen | first13 = C. -W. | last14 = Leibowitz | first14 = E.| last15 = Paparo | first15 = M.| last16 = Baran | first16 = A.| last17 = Charpinet | first17 = S.| last18 = Dolez | first18 = N.| last19 = Kawaler | first19 = S.| last20 = Kurtz | first20 = D.| last21 = Moskalik | first21 = P.| last22 = Riddle | first22 = R.| last23 = Zola | first23 = S.|s2cid=4342338}}</ref>
* [[Methods of detecting extrasolar planets#Reflection and emission modulations|Reflection/emission modulations]]
:When a planet orbits very close to a star, it catches a considerable amount of starlight. As the planet orbits the star, the amount of light changes due to planets having phases from Earth's viewpoint or planets glowing more from one side than the other due to temperature differences.<ref>{{cite journal |last1=Jenkins |first1=J. M. |last2=Doyle |first2=Laurance R. |date=20 September 2003 |title=Detecting reflected light from close-in giant planets using space-based photometers |journal=Astrophysical Journal |volume=1 |issue=595 |pages=429–445 |arxiv=astro-ph/0305473 |bibcode=2003ApJ...595..429J |doi=10.1086/377165 |s2cid=17773111}}</ref>
* [[Methods of detecting extrasolar planets#Relativistic beaming|Relativistic beaming]]
:Relativistic beaming measures the observed flux from the star due to its motion. The brightness of the star changes as the planet moves closer or further away from its host star.<ref>{{cite journal
 |arxiv=astro-ph/0303212
 |bibcode=2003ApJ...588L.117L
 |doi=10.1086/375551
 |title=Periodic Flux Variability of Stars due to the Reflex Doppler Effect Induced by Planetary Companions
 |date=2003
 |last1=Loeb |first1=A.
 |last2=Gaudi |first2=B. S.
 |journal=The Astrophysical Journal Letters
 |volume=588 |issue=2 |pages=L117
|s2cid=10066891
 }}</ref>
* [[Methods of detecting extrasolar planets#Ellipsoidal variations|Ellipsoidal variations]]
:Massive planets close to their host stars can slightly deform the shape of the star. This causes the brightness of the star to slightly deviate depending on how it is rotated relative to Earth.<ref>{{Cite web|last=Atkinson|first=Nancy|date=2013-05-13|title=Using the Theory of Relativity and BEER to Find Exoplanets|url=https://www.universetoday.com/102112/using-the-theory-of-relativity-and-beer-to-find-exoplanets/|access-date=2023-02-12|website=Universe Today|language=en-US}}</ref>
* [[Methods of detecting extrasolar planets#Polarimetry|Polarimetry]]
:With the polarimetry method, a polarized light reflected off the planet is separated from unpolarized light emitted from the star. No new planets have been discovered with this method, although a few already discovered planets have been detected with this method.<ref>{{Cite journal | doi = 10.1017/S1743921306009252| title = Search and investigation of extra-solar planets with polarimetry| journal = Proceedings of the International Astronomical Union| volume = 1| page = 165| year = 2006| last1 = Schmid | first1 = H. M.| last2 = Beuzit | first2 = J. -L. | last3 = Feldt | first3 = M.| last4 = Gisler | first4 = D.| last5 = Gratton | first5 = R.| last6 = Henning | first6 = T. | last7 = Joos | first7 = F.| last8 = Kasper | first8 = M.| last9 = Lenzen | first9 = R.| last10 = Mouillet | first10 = D.| last11 = Moutou | first11 = C.| last12 = Quirrenbach | first12 = A.| last13 = Stam | first13 = D. M.| last14 = Thalmann | first14 = C.| last15 = Tinbergen | first15 = J.| last16 = Verinaud | first16 = C.| last17 = Waters | first17 = R.| last18 = Wolstencroft | first18 = R.| bibcode = 2006dies.conf..165S| doi-access = free}}</ref><ref>{{Cite journal | doi = 10.1086/527320| title = First Detection of Polarized Scattered Light from an Exoplanetary Atmosphere| journal = The Astrophysical Journal| volume = 673| issue = 1| pages = L83| year = 2008| last1 = Berdyugina | first1 = S. V.| last2 = Berdyugin | first2 = A. V.| last3 = Fluri | first3 = D. M.| last4 = Piirola | first4 = V. | bibcode=2008ApJ...673L..83B|arxiv = 0712.0193 | s2cid = 14366978}}</ref>
* [[Methods of detecting extrasolar planets#Circumstellar disks|Circumstellar disks]]
:Disks of space dust surround many stars, thought to originate from collisions among asteroids and comets. The dust can be detected because it absorbs starlight and re-emits it as [[infrared]] radiation. Features on the disks may suggest the presence of planets, though this is not considered a definitive detection method.