Editing Proxima Centauri (section)

==Planetary system==
{{OrbitboxPlanet begin
| name = Proxima Centauri
| table_ref={{efn|<ref name=Guillem2016>
{{cite journal
 | last1 = Anglada-Escudé    | first1  = Guillem
 | last2 = Amado      | first2 = Pedro J.    | last3 = Barnes   | first3 = John
 | last4 = Berdiñas   | first4 = Zaira M.    | last5 = Butler   | first5 = R. Paul
 | last6 = Coleman    | first6  = Gavin A.L.
 | last7 = {{nobr|de la Cueva}} | first7  = Ignacio
 | last8 = Dreizler   | first8  = Stefan     | last9 = Endl     | first9 = Michael
 | last10 = Giesers   | first10 = Benjamin
 | last11 = Jeffers   | first11 = Sandra V.
 | last12 = Jenkins   | first12 = James S.
 | last13 = Jones     | first13 = Hugh R.A.
 | last14 = Kiraga    | first14 = Marcin     | last15 = Kürster | first15 = Martin
 | last16 = López-González  | first16 = María J.
 | last17 = Marvin    | first17 = Christopher J.
 | last18 = Morales   | first18 = Nicolás    | last19 = Morin   | first19 = Julien
 | last20 = Nelson    | first20 = Richard P.
 | last21 = Ortiz     | first21 = José L.    | last22 = Ofir    | first22 = Aviv
 | last23 = Paardekooper    | first23 = Sijme-Jan
 | last24 = Reiners   | first24 = Ansgar     | last25 = Rodríguez | first25 = Eloy
 | last26 = Rodríguez-López | first26 = Cristina
 | last27 = Sarmiento | first27 = Luis F.
 | last28 = Strachan  | first28 = John P.
 | last29 = Tsapras   | first29 = Yiannis    | last30 = Tuomi    | first30 = Mikko
 | last31  = Zechmeister    | first31 = Mathias
 | display-authors=6
 | year    = 2016
 | title   = A terrestrial planet candidate in a temperate orbit around Proxima Centauri
 | journal = [[Nature (journal)|Nature]]
 | volume  = 536    | issue = 7617    | pages = 437–440
 | pmid    = 27558064   | doi     = 10.1038/nature19106
 | s2cid   = 4451513    | bibcode = 2016Natur.536..437A
 | arxiv   = 1609.03449
 | url = https://www.nature.com/articles/nature19106
 | via = nature.com 
}}
</ref><ref name=Li-2017/><ref name=Damasso2020/><ref name=KervellaArenou2020>
{{cite journal
 |last1=Kervella  |first1=Pierre
 |last2=Arenou    |first2=Frédéric
 |last3=Schneider |first3=Jean
 |year=2020
 |title=Orbital inclination and mass of the exoplanet candidate Proxima&nbsp;c
 |journal=[[Astronomy & Astrophysics]]
 |volume=635 |page=L14
 |arxiv=2003.13106
 |doi=10.1051/0004-6361/202037551 |issn=0004-6361
 |bibcode= 2020A&A...635L..14K   |s2cid=214713486
}}</ref><ref name="Suárez MascareñoFaria2020"/><ref name=BenedictMcArthur2020>
{{cite journal
 |last1=Benedict |first1=G. Fritz
 |last2=McArthur |first2=Barbara E.
 |date=16 June 2020
 |title=A moving target: Revising the mass of Proxima Centauri&nbsp;c
 |journal=[[Research Notes of the AAS]]
 |volume=4  |issue=6  |page=86
 |doi=10.3847/2515-5172/ab9ca9 |doi-access=free
 |bibcode=2020RNAAS...4...86B |s2cid=225798015
}}
</ref><ref name="FariaSuárezMascareñoSilva2022"/>
}}
}}
{{OrbitboxPlanet hypothetical
| exoplanet = [[Proxima Centauri d|d]]
| mass_earth = {{Val|0.26|0.05|p=≥}}
| period = {{Val|5.122|0.002|0.0036}} 
| semimajor = {{Val|0.02885|0.00019|0.00022}}
| radius_earth = {{Val|0.81|0.08|p=[[wiktionary:≙|≙]]}}  
| eccentricity = {{Val|0.04|0.15|0.04}}
| inclination =
| status = unconfirmed{{efn|It is argued that Proxima d is confirmed because it could be detected via different methods of measuring the same radial velocity data from which Proxima&nbsp;d was discovered.<ref name="ArtigauCadieux2022"/> However, Proxima&nbsp;d is considered a candidate exoplanet by its discoverers and the [[NASA Exoplanet Archive]], because it has not been independently confirmed by more than one observatory.<ref name="Faria2022">{{cite journal |last1=Faria |first1=J. P. |last2=Suárez Mascareño |first2=A. |last3=Figueira |first3=P. |last4=Silva |first4=A. M. |last5=Damasso |first5=M. |last6=Demangeon |first6=O. |last7=Pepe |first7=F. |last8=Santos |first8=N. C. |last9=Rebolo |first9=R. |last10=Cristiani |first10=S. |last11=Adibekyan |first11=V. |display-authors=2 |date=January 4, 2022 |title=A candidate short-period sub-Earth orbiting Proxima Centauri |url=https://www.eso.org/public/archives/releases/sciencepapers/eso2202/eso2202a.pdf |journal=Astronomy & Astrophysics |publisher=European Southern Observatory |volume=658 |pages=17 |arxiv=2202.05188 |bibcode=2022A&A...658A.115F |doi=10.1051/0004-6361/202142337 |doi-access=free |last35=Tabernero |last23=Lo Curto |first18=X. |last19=Ehrenreich |first19=D. |last20=González Hernández |first20=J. I. |last21=Hara |last15=Cabral |first22=J. |first28=G. |last24=Lovis |first23=G. |first17=P. |first24=C. |last25=Martins |first25=C. J. A. P. |last26=Mégevand |first26=D. |last27=Mehner |first27=A. |last28=Micela |first21=N. |last18=Dumusque |last17=Di Marcantonio |first30=N. J. |first36=S. |last31=Pallé |first31=E. |last32=Poretti |first32=E. |last33=Sousa |first33=S. G. |last34=Sozzetti |first34=A. |last36=Udry |first15=A. |first29=P. |last37=Zapatero Osorio |first16=V. |first37=M. R. |first14=S. C. C. |last14=Barros |first13=R. |last13=Allart |first12=Y. |last12=Alibert |last30=Nunes |last29=Molaro |last16=D'Odorico |last22=Lillo-Box |first35=H.}}</ref>}}
}}
{{OrbitboxPlanet
| exoplanet = [[Proxima Centauri b|b]]
| mass_earth = ≥{{val|1.07|0.06}}
| period = {{Val|11.1868|0.0029|0.0031}}
| semimajor = {{Val|0.04856|0.00030|0.00030}}
| radius_earth = {{Val|1.30|1.20|0.62|p=≙}} 
| eccentricity = {{Val|0.02|0.04|0.02}}
| inclination =
}}
{{OrbitboxPlanet hypothetical
| exoplanet = [[Proxima Centauri c|c]]
| mass_earth = {{Val|7|1}}
| period = {{Val|1928|20|fmt=commas}}
| semimajor = {{Val|1.489|0.049}}
| radius_earth =
| eccentricity = {{Val|0.04|0.01}}
| inclination ={{Val|133|1}}
| status = disputed<ref name=ArtigauCadieux2022>
{{cite journal
 |last1=Artigau   |first1=Étienne        |last2=Cadieux   |first2=Charles
 |last3=Cook      |first3=Neil J.        |last4=Doyon     |first4=René
 |last5=Vandal    |first5=Thomas         |last6=Donati    |first6=Jean-Françcois
 |last7=Moutou    |first7=Claire         |last8=Delfosse  |first8=Xavier
 |last9=Fouqué    |first9=Pascal         |last10=Martioli |first10=Eder
 |last11=Bouchy   |first11=François      |last12=Parsons  |first12=Jasmine
 |last13=Carmona  |first13=Andres        |last14=Dumusque |first14=Xavier
 |last15=Astudillo-Defru |first15=Nicola |last16=Bonfils  |first16=Xavier
 |last17=Mignon   |first17=Lucille
 |display-authors=6
 |date=23 June 2022
 |publication-date=8 August 2022
 |title=Line-by-line velocity measurements, an outlier-resistant method for precision velocimetry
 |journal=[[The Astronomical Journal]]
 |volume=164  |issue=3  |page=84
 |arxiv=2207.13524  |bibcode=2022AJ....164...84A
 |doi=10.3847/1538-3881/ac7ce6  |doi-access=free
}}
</ref><ref name=EPE>
{{cite encyclopedia
 |title=Proxima Centauri&nbsp;c
 |encyclopedia=[[Extrasolar Planets Encyclopaedia]]
 |url=https://exoplanet.eu/catalog/proxima_centauri_c--7082/
 |access-date=30 July 2022
}}
</ref>
}}
{{Orbitbox end}}
[[File:Proxima planetary system new.jpg|thumb|upright=1.2|Schematic of the three planets (d, b, and c) of the Proxima Centauri system, with the [[habitable zone]] identified]]
As of 2022, three planets (one confirmed and two candidates) have been detected in orbit around Proxima Centauri, with one possibly being among the lightest ever detected by radial velocity ("d"), one close to Earth's size within the [[habitable zone]] ("b"), and a possible [[gas dwarf]] that orbits much further out than the inner two ("c"), although its status remains disputed.

Searches for exoplanets around Proxima Centauri date to the late 1970s. In the 1990s, multiple measurements of Proxima Centauri's radial velocity constrained the maximum mass that a detectable companion could possess.<ref name=apj118>
{{cite journal
 |last1=Benedict   |first1=G. Fritz     |last2=Chappell |first2=D.W.
 |last3=Nelan      |first3=E.           |last4=Jefferys |first4=W.H.
 |last5=van&nbsp;Altena |first5=W.      |last6=Lee      |first6=J.
 |last7=Cornell    |first7=D.           |last8=Shelus   |first8=P.J.
 |display-authors=6
 |year=1999
 |title=Interferometric astrometry of Proxima Centauri and Barnard's Star using Hubble Space Telescope fine guidance sensor. 3:&nbsp;Detection limits for substellar companions
 |journal=[[The Astronomical Journal]]
 |volume=118  |issue=2  |pages=1086–1100
 |bibcode=1999AJ....118.1086B |doi=10.1086/300975
 |s2cid=18099356  |arxiv=astro-ph/9905318
}}
</ref><ref name=aaal344>
{{cite journal
 |last1=Kürster  |first1=M.       |last2=Hatzes   |first2=A.P.
 |last3=Cochran  |first3=W.D.     |last4=Döbereiner |first4=S.
 |last5=Dennerl  |first5=K.       |last6=Endl     |first6=M.
 |year=1999
 |title=Precise radial velocities of Proxima Centauri. Strong constraints on a substellar companion
 |journal=[[Astronomy & Astrophysics Letters]]
 |volume=344 |pages=L5–L8
 |arxiv=astro-ph/9903010 |bibcode=1999A&A...344L...5K
}}
</ref>
The activity level of the star adds noise to the radial velocity measurements, complicating detection of a companion using this method.<ref>
{{cite journal
 | last1=Saar    | first1=Steven H.
 | last2=Donahue | first2=Robert A.
 | year=1997
 | title=Activity-related radial velocity variation in cool stars
 | journal=Astrophysical Journal
 | volume=485  | issue=1  | pages=319–326
 | doi=10.1086/304392  | s2cid=17628232
 | bibcode=1997ApJ...485..319S
 | url=http://pdfs.semanticscholar.org/f853/b15f7c178a7f9dd1735752d2601c6202ee63.pdf
 | url-status=dead
 | archive-url=https://web.archive.org/web/20190309110644/http://pdfs.semanticscholar.org/f853/b15f7c178a7f9dd1735752d2601c6202ee63.pdf
 | archive-date=2019-03-09
}}
</ref>
In 1998, an examination of Proxima Centauri using the [[Faint Object Spectrograph]] on board the Hubble Space Telescope appeared to show evidence of a companion orbiting at a distance of about 0.5&nbsp;AU.<ref>
{{cite journal
 | last1=Schultz    | first1=A.B.     | last2=Hart       | first2=H.M.
 | last3=Hershey    | first3=J.L.     | last4=Hamilton   | first4=F.C.
 | last5=Kochte     | first5=M.       | last6=Bruhweiler | first6=F.C.
 | last7=Benedict   | first7=G.F.     | last8=Caldwell   | first8=John
 | last9=Cunningham | first9=C.       | last10=Wu        | first10=Nailong
 | last11=Franz     | first11=O.G.    | last12=Keyes     | first12=C.D.
 | last13=Brandt    | first13=J.C.
 | display-authors=6
 | year=1998
 | title=A possible companion to Proxima Centauri
 | journal=[[The Astronomical Journal]]
 | volume=115  | issue=1  | pages=345–350
 | doi=10.1086/300176  | bibcode=1998AJ....115..345S
 | s2cid=120356725
}}
</ref>
A subsequent search using the [[Wide Field and Planetary Camera 2]] failed to locate any companions.<ref name=apj119>
{{cite journal
 | last1=Schroeder | first1=Daniel J.   | last2=Golimowski | first2=David A.
 | last3=Brukardt  | first3=Ryan A.     | last4=Burrows    | first4=Christopher J.
 | last5=Caldwell  | first5=John J.     | last6=Fastie     | first6=William G.
 | last7=Ford      | first7=Holland C.  | last8=Hesman     | first8=Brigette
 | last9=Kletskin  | first9=Ilona       | last10=Krist     | first10=John E.
 | last11=Royle    | first11=Patricia   | last12=Zubrowski | first12=Richard A.
 | display-authors=6
 | year=2000
 | title=A search for faint companions to nearby stars using the Wide Field Planetary Camera&nbsp;2
 | journal=[[The Astronomical Journal]]
 | volume=119  | issue=2  | pages=906–922
 | doi=10.1086/301227  | doi-access=free
 | bibcode=2000AJ....119..906S
}}
</ref> [[Astrometry|Astrometric]] measurements at the [[Cerro Tololo Inter-American Observatory]] appear to rule out a [[Jupiter (planet)|Jupiter]]-sized planet with an orbital period of 2−12&nbsp;years.<ref>
{{cite journal
 |last1=Lurie   |first1=John C.         |last2=Henry  |first2=Todd J.
 |last3=Jao     |first3=Wei-Chun        |last4=Quinn  |first4=Samuel N.
 |last5=Winters |first5=Jennifer G.     |last6=Ianna  |first6=Philip A.
 |last7=Koerner |first7=David W.        |last8=Riedel |first8=Adric R.
 |last9=Subasavage |first9=John P.
 |display-authors=6
 |title=The Solar neighborhood. XXXIV. A search for planets orbiting nearby M&nbsp;dwarfs using astrometry
 |journal=[[The Astronomical Journal]]
 |volume=148  |issue=5  |id=91  |page=12
 |date=November 2014
 |doi=10.1088/0004-6256/148/5/91   |arxiv=1407.4820
 |bibcode=2014AJ....148...91L   |s2cid=118492541
}}
</ref>

In 2017, a team of astronomers using the [[Atacama Large Millimeter Array]] reported detecting a belt of cold dust orbiting Proxima Centauri at a range of 1−4&nbsp;AU from the star. This dust has a temperature of around 40&nbsp;K and has a total estimated mass of 1% of the planet Earth. They tentatively detected two additional features: a cold belt with a temperature of 10&nbsp;K orbiting around 30&nbsp;AU and a compact emission source about 1.2&nbsp;arcseconds from the star. There was a hint at an additional warm dust belt at a distance of 0.4&nbsp;AU from the star.<ref name=Guillem2017/> However, upon further analysis, these emissions were determined to be most likely the result of a large flare emitted by the star in March&nbsp;2017. The presence of dust within 4&nbsp;AU radius from the star is not needed to model the observations.<ref name=sd2018>
{{cite news
 |title=Proxima Centauri's no good, very bad day
 |date=26 February 2018
 |website=[[Science Daily]]
 |url=https://www.sciencedaily.com/releases/2018/02/180226103341.htm
 |access-date=1 March 2018
}}
</ref><ref name=MacGregor>
{{cite journal
 |last1=MacGregor |first1=Meredith A.    |last2=Weinberger |first2=Alycia J.
 |last3=Wilner    |first3=David J.       |last4=Kowalski   |first4=Adam F.
 |last5=Cranmer   |first5=Steven R.
 |year=2018
 |title=Detection of a millimeter flare from Proxima Centauri
 |journal=[[Astrophysical Journal Letters]]
 |volume=855 |issue=1 |page =L2
 |arxiv=1802.08257 |bibcode=2018ApJ...855L...2M
 |doi=10.3847/2041-8213/aaad6b |s2cid=119287614 |doi-access=free
}}
</ref>

===Planet b===
{{main|Proxima Centauri b}}

Proxima Centauri&nbsp;b, or Alpha Centauri&nbsp;Cb, orbits the star at a distance of roughly {{convert|0.05|AU|e6km|abbr=unit}} with an orbital period of approximately 11.2&nbsp;Earth days. Its estimated mass is at least 1.07&nbsp;times that of the [[Earth]].<ref name="FariaSuárezMascareñoSilva2022"/> Moreover, the equilibrium temperature of Proxima Centauri&nbsp;b is estimated to be within the range where water could exist as liquid on its surface; thus, placing it within the [[habitable zone]] of Proxima Centauri.<ref name=Guillem2016/><ref name=NYT-20160824>
{{cite news
 |last=Chang |first=Kenneth
 |date=24 August 2016
 |title=One star over, a planet that might be another Earth
 |newspaper=[[The New York Times]]
 |url=https://www.nytimes.com/2016/08/25/science/earth-planet-proxima-centauri.html
 |access-date=24 August 2016}}</ref><ref name=telegraph20160824>
{{cite news
 |last =Knapton |first =Sarah
 |date=24 August 2016
 |title=Proxima&nbsp;b: Alien life could exist on 'second Earth' found orbiting our nearest star in Alpha Centauri system
 |newspaper=[[The Daily Telegraph|The Telegraph]]  |publisher=[[Telegraph Media Group]]
 |url=https://www.telegraph.co.uk/science/2016/08/24/proxima-b-alien-life-could-exist-on-second-earth-found-orbiting/
 |access-date=24 August 2016 | url-access=subscription  |url-status=live
 |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/science/2016/08/24/proxima-b-alien-life-could-exist-on-second-earth-found-orbiting/
 |archive-date=12 January 2022
}}{{cbignore}}
</ref>

The first indications of the [[exoplanet]] Proxima Centauri&nbsp;b were found in 2013 by [[Mikko Tuomi]] of the [[University of Hertfordshire]] from archival observation data.<ref name=prd>
{{cite news
 |title=Proxima&nbsp;b is our neighbor ... better get used to it!
 |date=24 August 2016
 |website=Pale Red Dot
 |url=https://palereddot.org/proxima-b-is-our-closest-neighbor-better-get-used-to-it/
 |access-date=24 August 2016 |url-status=dead
 |archive-url=https://web.archive.org/web/20200513054609/https://palereddot.org/proxima-b-is-our-closest-neighbor-better-get-used-to-it/
 |archive-date=13 May 2020
}}
</ref><ref>
Aron, Jacob. August 24, 2016. [https://www.newscientist.com/article/mg23130884-100-proxima-b-closest-earth-like-planet-discovered-right-next-door/ Proxima b: Closest Earth-like planet discovered right next door]. ''New Scientist''. Retrieved August 24, 2016
</ref> To confirm the possible discovery, a team of astronomers launched the Pale Red Dot<ref group="nb">
"[[Pale Blue Dot]]" is a reference to a distant photo of Earth taken by [[Voyager 1]].
</ref>
project in January&nbsp;2016.
<ref>
{{cite press release
 |title=Follow a live planet hunt!
 |url=https://www.eso.org/public/announcements/ann16002/
 |date=January 15, 2016
 |publisher=[[European Southern Observatory]]
 |access-date=24 August 2016}}</ref> On 24&nbsp;August 2016, the team of 31&nbsp;scientists from all around the world,<ref>
{{cite news
 |last=Feltman |first=Rachel
 |date=24 August 2016
 |title=Scientists say they've found a planet orbiting Proxima Centauri, our closest neighbor
 |newspaper=[[The Washington Post]]
 |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2016/08/24/scientists-may-have-found-a-planet-orbiting-proxima-centauri-our-closest-star/
}}
</ref>
led by Guillem Anglada-Escudé of [[Queen Mary University of London]], confirmed the existence of [[Proxima Centauri b|Proxima Centauri&nbsp;b]]<ref name=spacecom>{{cite news
 |first =Samantha |last =Mathewson
 |date=24 August 2016
 |title=Proxima&nbsp;b by the numbers: Possibly Earth-like world at the next star over
 |website=Space.com
 |url=http://www.space.com/33837-earth-like-planet-proxima-centauri-numbers.html
 |access-date=August 25, 2016
}}
</ref>
through a peer-reviewed article published in ''[[Nature (journal)|Nature]]''.<ref name=Guillem2016/><ref name="Nature 24 August 2016">
{{cite journal
 |last =Witze |first =Alexandra
 |date=24 August 2016
 |title=Earth-sized planet around nearby star is astronomy dream come true
 |journal=[[Nature (journal)|Nature]]
 |volume=536  |issue=7617  |pages=381–382
 |doi=10.1038/nature.2016.20445  |doi-access=free
 |pmid=27558041  |bibcode=2016Natur.536..381W
}}
</ref>
The measurements were performed using two spectrographs: [[High Accuracy Radial Velocity Planet Searcher|HARPS]] on the [[ESO 3.6 m Telescope]] at [[La Silla Observatory]] and [[Very Large Telescope#Instruments|UVES]] on the 8&nbsp;m [[Very Large Telescope]] at [[Paranal Observatory]].<ref name=Guillem2016/> Several attempts to detect a [[Transit (astronomy)|transit]] of this planet across the face of Proxima Centauri have been made. A transit-like signal appearing on 8&nbsp;September 2016, was tentatively identified, using the [[Bright Star Survey Telescope]] at the [[Zhongshan Station (Antarctica)|Zhongshan Station]] in Antarctica.<ref name=Liu2018>
{{cite journal
 |last1=Liu      |first1=Hui-Gen          |last2=Jiang     |first2=Peng
 |last3=Huang    |first3=Xingxing         |last4=Yu        |first4=Zhou-Yi
 |last5=Yang     |first5=Ming             |last6=Jia       |first6=Minghao
 |last7=Awiphan  |first7=Supachai         |last8=Pan       |first8=Xiang
 |last9=Liu      |first9=Bo               |last10=Zhang    |first10=Hongfei
 |last11=Wang    |first11=Jian            |last12=Li       |first12=Zhengyang
 |last13=Du      |first13=Fujia           |last14=Li       |first14=Xiaoyan
 |last15=Lu      |first15=Haiping         |last16=Zhang    |first16=Zhiyong
 |last17=Tian    |first17=Qi-Guo          |last18=Li       |first18=Bin
 |last19=Ji      |first19=Tuo             |last20=Zhang    |first20=Shaohua
 |last21=Shi     |first21=Xiheng          |first22=Ji      |last22=Wang
 |first23=Ji-Lin |last23=Zhou             |first24=Hongyan |last24=Zhou
 |display-authors=6
 |date=January 2018
 |title=Searching for the transit of the Earth-mass exoplanet Proxima Centauri&nbsp;b in Antarctica: Preliminary result
 |journal=[[The Astronomical Journal]]
 |volume=155 |issue=1 |id=12 |page=10
 |doi=10.3847/1538-3881/aa9b86  |doi-access=free
 |bibcode=2018AJ....155...12L  |s2cid=54773928
 |arxiv=1711.07018
}}
</ref>

In 2016, in a paper that helped to confirm Proxima Centauri&nbsp;b's existence, a second signal in the range of 60–500&nbsp;days was detected. However, stellar activity and inadequate sampling causes its nature to remain unclear.<ref name=Guillem2016/>

===Planet c===
{{main|Proxima Centauri c}}

Proxima Centauri&nbsp;c is a candidate [[super-Earth]] or [[gas dwarf]] about {{nobr|7 {{Earth mass}}}} orbiting at roughly {{convert|1.5|AU|km}} every {{convert|1900|days|years}}.<ref name=SA-20190412/> If Proxima Centauri&nbsp;b were the star's Earth, Proxima Centauri&nbsp;c would be equivalent to Neptune. Due to its large distance from Proxima Centauri, it is unlikely to be habitable, with a low equilibrium temperature of around 39&nbsp;K.<ref name=ProximaC/> The planet was first reported by Italian astrophysicist Mario Damasso and his colleagues in April&nbsp;2019.<ref name=ProximaC>
{{cite news
 |first=Mike |last=Wall
 |date=12 April 2019
 |title=Possible 2nd&nbsp;planet spotted around Proxima Centauri
 |website=Space.com
 |url=https://www.space.com/proxima-centauri-possible-second-exoplanet.html
 |access-date=12 April 2019
}}
</ref><ref name=SA-20190412>
{{cite news
 |first=Lee |last=Billings
 |date=12 April 2019
 |title=A second planet may orbit Earth's nearest neighboring star
 |magazine=[[Scientific American]]
 |url=https://www.scientificamerican.com/article/a-second-planet-may-orbit-earths-nearest-neighboring-star/
 |access-date=12 April 2019
}}
</ref>
Damasso's team had noticed minor movements of Proxima Centauri in the [[Methods of detecting exoplanets#Radial velocity|radial velocity]] data from the ESO's HARPS instrument, indicating a possible additional planet orbiting Proxima Centauri.<ref name=ProximaC/> In 2020, the planet's existence was confirmed by Hubble [[astrometry]] data from {{Circa|1995}}.<ref name=McDonald>
{{cite press release
 |last=Benedict |first=Fritz
 |date=2 June 2020
 |title=Texas astronomer uses 25&nbsp;year-old Hubble data to confirm [lanet Proxima Centauri&nbsp;c
 |series=[[McDonald Observatory]]
 |publisher=[[University of Texas]]
 |url=https://mcdonaldobservatory.org/news/releases/20200602
}}
</ref>
A possible direct imaging counterpart was detected in the infrared with the [[Spectro-Polarimetric High-Contrast Exoplanet Research|SPHERE]], but the authors admit that they "did not obtain a clear detection." If their candidate source is in fact Proxima Centauri&nbsp;c, it is too bright for a planet of its mass and age, implying that the planet may have a [[ring system]] with a radius of around {{nobr|5 {{Jupiter radius|link=y}}.<ref name=Gratton2020/>}} However, {{harvp|Artigau|Cadieux|Cook|Doyon|Vandal|2022}} disputed the radial velocity confirmation of the planet.<ref name=ArtigauCadieux2022/>

===Planet d===
{{main|Proxima Centauri d}}

In 2019, a team of astronomers revisited the data from [[ESPRESSO]] about Proxima Centauri&nbsp;b to refine its mass. While doing so, the team found another radial velocity spike with a periodicity of 5.15&nbsp;days. They estimated that if it were a planetary companion, it would be no less than 0.29&nbsp;Earth masses.<ref name="Suárez MascareñoFaria2020"/> Further analysis confirmed the signal's existence leading up to the announcement of the candidate planet in February&nbsp;2022.<ref name="FariaSuárezMascareñoSilva2022"/>

===Habitability===
{{See also|Habitability of red dwarf systems}}
{{stack|[[File:Proxima Centauri and its planet compared to the Solar System.jpg|thumb|upright=1.2|Overview and comparison of the orbital distance of the [[habitable zone]]]]}}
Before the discovery of Proxima Centauri&nbsp;b, the TV documentary ''[[Extraterrestrial (TV documentary)#Episode 1: Aurelia|Alien Worlds]]'' hypothesized that a life-sustaining planet could exist in orbit around Proxima Centauri or other red dwarfs. Such a planet would lie within the habitable zone of Proxima Centauri, about {{convert|0.023|–|0.054|AU|e6km|abbr=unit}} from the star, and would have an orbital period of 3.6–14&nbsp;days.<ref>
{{cite conference
 |last1=Endl     |first1=M.      |last2=Kuerster |first2=M.
 |last3=Rouesnel |first3=F.      |last4=Els      |first4=S.
 |last5=Hatzes   |first5=A.P.    |last6=Cochran  |first6=W.D.
 |date=18–21 June 2002
 |title=Extrasolar terrestrial planets: Can we detect them already?
 |editor-first=Drake  |editor-last=Deming
 |conference=Scientific Frontiers in Research on Extrasolar Planets
 |pages=75–79
 |location=Washington, DC
 |arxiv=astro-ph/0208462 |bibcode=2003ASPC..294...75E
}}
</ref>
A planet orbiting within this zone may experience [[tidal locking]] to the star. If the orbital eccentricity of this hypothetical planet were low, Proxima Centauri would move little in the planet's sky, and most of the surface would experience either day or night perpetually. The presence of an atmosphere could serve to redistribute heat from the star-lit side to the far side of the planet.<ref name="tarter">{{cite journal |title=A reappraisal of the habitability of planets around M dwarf stars |journal=[[Astrobiology (journal)|Astrobiology]] |date=2007 |volume=7 |issue=1 |pages=30–65 |doi=10.1089/ast.2006.0124 |pmid=17407403 |bibcode=2007AsBio...7...30T |arxiv=astro-ph/0609799 | last1=Tarter | first1=Jill C. | last2=Mancinelli | first2=Rocco L. | last3=Aurnou | first3=Jonathan M. | last4=Backman | first4=Dana E. | last5=Basri | first5=Gibor S. | last6=Boss | first6=Alan P. | last7=Clarke | first7=Andrew | last8=Deming | first8=Drake|s2cid=10932355 }}</ref>

Proxima Centauri's [[Solar flare|flare]] outbursts could erode the atmosphere of any planet in its habitable zone, but the documentary's scientists thought that this obstacle could be overcome. [[Gibor Basri]] of the [[University of California, Berkeley]] argued: "No one [has] found any showstoppers to habitability." For example, one concern was that the torrents of charged particles from the star's flares could strip the atmosphere off any nearby planet. If the planet had a strong magnetic field, the field would deflect the particles from the atmosphere; even the slow rotation of a tidally locked planet that spins once for every time it orbits its star would be enough to generate a magnetic field, as long as part of the planet's interior remained molten.<ref>{{cite journal |last=Alpert |first=Mark |date=November 2005 |title=Red star rising |journal=Scientific American |volume=293 |issue=5 |pages=28 |doi=10.1038/scientificamerican1105-28 |pmid=16318021 |bibcode=2005SciAm.293e..28A}}</ref>

Other scientists, especially proponents of the [[Rare Earth hypothesis]],<ref>{{cite book |first1=Peter D. |last1=Ward |author-link=Peter Ward (paleontologist) |last2=Brownlee |first2=Donald |author-link2=Donald E. Brownlee |date=2000 |title=Rare Earth: why complex life is uncommon in the universe |publisher=[[Springer Publishing]] |isbn=978-0-387-98701-9}}</ref> disagree that red dwarfs can sustain life. Any exoplanet in this star's habitable zone would likely be tidally locked, resulting in a relatively weak planetary [[magnetic moment]], leading to strong atmospheric erosion by [[coronal mass ejection]]s from Proxima Centauri.<ref name="Khodachenko">{{cite journal |title=Coronal Mass Ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. I. CME impact on expected magnetospheres of earth-like exoplanets in close-in habitable zones |journal=Astrobiology |date=2007 |volume=7 |issue=1 |pages=167–184 |doi=10.1089/ast.2006.0127 |pmid=17407406 |bibcode=2007AsBio...7..167K | last1=Khodachenko | first1=Maxim L. | last2=Lammer | first2=Helmut | last3=Grießmeier | first3=Jean-Mathias | last4=Leitner | first4=Martin | last5=Selsis | first5=Franck | last6=Eiroa | first6=Carlos | last7=Hanslmeier | first7=Arnold | last8=Biernat | first8=Helfried K. }}</ref> In December 2020, a candidate [[SETI]] radio signal [[BLC-1]] was announced as potentially coming from the star.<ref name="OCallaghan2000">{{Cite web
 | last=O'Callaghan | first=Jonathan | date=2020-12-18
 | title=Alien Hunters Discover Mysterious Radio Signal from Proxima Centauri
 | url=https://www.scientificamerican.com/article/alien-hunters-discover-mysterious-signal-from-proxima-centauri/
 | access-date=2020-12-19
 | website=Scientific American | language=en }}</ref> The signal was later determined to be human-made radio interference.<ref>{{cite journal
 | title=Mysterious 'alien beacon' was false alarm
 | first=Alexandra | last=Witze
 | journal=Nature | date=25 October 2021
 | volume=599 | issue=7883 | pages=20–21 | doi=10.1038/d41586-021-02931-7 | pmid=34697482
| bibcode=2021Natur.599...20W | s2cid=239887089 | doi-access=free }}</ref>