Proxima Centauri c (also calledProxima c[2] orAlpha Centauri Cc) is a disputedexoplanet candidate, proposed to be orbiting thered dwarf starProxima Centauri, which is the closest star to theSun and part of a triplestar system. It is located approximately 4.2 light-years (1.3 parsecs; 40 trillion kilometres; 25 trillion miles) fromEarth in the constellation ofCentaurus. If Proxima c exists, this would make it, along withProxima b andProxima d, theclosest known exoplanets to theSolar System.
As originally proposed, Proxima Centauri c would be asuper-Earth ormini-Neptune about 7 times as massive as Earth,[a] orbiting at roughly 1.49 AU (223 million km; 139 million mi) every 1,928 days (5.28 years).[3] Due to its large mass and its distance from Proxima Centauri, the exoplanet would be uninhabitable and too cold for liquid water to exist on the surface, with an equilibrium temperature of approximately 39 K (−234.2 °C; −389.5 °F).[1][4] According to a 2025 study, the originally proposed planet most likely does not exist, but there may be a smaller planet with a similar orbit.[5]
The planet does nottransit its parent star from the point of view of an Earth-based observer.[6]
The planet candidate was first reported by Italian astrophysicistMario Damasso and his colleagues in April 2019. Damasso's team had noticed minor movements of Proxima Centauri in theradial velocity data from the ESO'sHARPS instrument, analyzed earlier by Ukrainian astrophysicistYakiv Pavlenko and his colleagues at theInstituto de Astrofísica de Canarias,[7][8][9] indicating a possible second planet orbiting Proxima Centauri.[10] The discovery was published on 15 January 2020.[1]
Subsequent studies in 2020 also found evidence for Proxima c viaastrometry,[2] includingHubble data fromc. 1995, allowing itsinclination and true mass to be determined.[3] Also in June 2020, a possibledirectly imaged counterpart of Proxima c was detected in the infrared withSPHERE, but the authors admit that they "did not obtain a clear detection".[11] If their candidate source is in fact Proxima Centauri c, it is too bright for a planet of its mass and age, implying that the planet may have aring system with a radius of around 5 RJ.[11] At the time, the multiple lines of evidence appeared to confirm the planet.[12]
However, a 2022 study questioned the planetary nature of the observedradial velocity signal corresponding to Proxima c, whose detection could not be recreated, attributing it to systematic effects.[13] As of 2025[update], evidence for Proxima c remains inconclusive; observations with theNIRPS spectrograph were unable to confirm it, but found hints of a lower-amplitude signal, different from the originally proposed planet, with a similar period.[5] Another 2025 study, reanalyzing Hubble and Gaia astrometry, estimated a mass of3.4+5.2 −3.4M🜨 for Proxima c, assuming a circular, face-on orbit. This is broadly consistent with previous estimates, but also consistent with a non-detection.[14]
^Gilbert, Emily A.; Barclay, Thomas; Kruse, Ethan; Quintana, Elisa V.; Walkowicz, Lucianne M. (2021), "No Transits of Proxima Centauri Planets in High-Cadence TESS Data",Frontiers in Astronomy and Space Sciences,8: 190,arXiv:2110.10702,Bibcode:2021FrASS...8..190G,doi:10.3389/fspas.2021.769371
^"Проксима Центавра може бути домом для другої планети [оновлено]".scienceukraine.com (in Ukrainian). 16 January 2020. Archived fromthe original on 2020-09-23.Автори використали наші результати, отримані у співпраці з групою вчених з Інституту астрофізики на Канарських о-вах, для того, щоб відкинути можливість пояснення довгоперіодичної варіації параметрів спектру Проксими явищами зоряної активності.
^Libralato, M.; Bedin, L.; Burgasser, A. (December 2025). "Astrometric Reconnaissance of Exoplanetary Systems (ARES). I. Methodology validation with HST point-source images of Proxima Centauri".Astronomy & Astrophysics.arXiv:2512.08533.
