|Discovered by||Damasso et al.|
|Discovery date||January 2020|
|Temperature||39 K (−234.2 °C; −389.5 °F)|
Proxima Centauri c (also called Proxima c or Alpha Centauri Cc) is a very strong exoplanet candidate[note 1] orbiting the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is located approximately 4.2 light-years (1.3 parsecs; 4.0×1013 kilometres) from Earth in the constellation of Centaurus, making it and Proxima b the closest known exoplanets to the Solar System.
Proxima Centauri c is a super-Earth or mini-Neptune about 7 times as massive as Earth, orbiting at roughly 1.49 astronomical units (223,000,000 km) every 1,928 days (5.28 yr). Due to its large distance from Proxima Centauri, the exoplanet is unlikely to be habitable, with a low equilibrium temperature of around 39K (-234 °C).
The planet was first reported by Italian astrophysicist Mario Damasso and his colleagues in April 2019. Damasso's team had noticed minor movements of Proxima Centauri in the radial velocity data from the ESO's HARPS instrument, indicating a possible second planet orbiting Proxima Centauri. The discovery was published in January 2020. In June 2020, the planet's existence was confirmed using Hubble astrometry data from c. 1995, allowing its inclination and true mass to be determined. Also in June 2020, a possible directly imaged counterpart of Proxima c was detected in the infrared with SPHERE, but the authors admit that they "did not obtain a clear detection". 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 a ring system with a radius of around 5 RJ.