Proxima Centauri b is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri in the constellation Centaurus. It can also be referred to as Proxima b, or Alpha Centauri Cb. The host star is the closest star to the Sun, at a distance of about 4.2 light-years (1.3 parsecs) from Earth, and is part of the larger triple star system Alpha Centauri. Proxima b and Proxima d, along with the currently disputed Proxima c, are the closest known exoplanets to the Solar System.
Proxima Centauri b orbits its parent star at a distance of about 0.04848 AU (7.253 million km; 4.506 million mi) with an orbital period of approximately 11.2 Earth days. Its other properties are only poorly understood, but it is probably a terrestrial planet with a minimum mass of 1.06 M🜨 and a slightly larger radius than that of Earth. The planet orbits within the habitable zone of its parent star; but it is not known whether it has an atmosphere, which would impact the habitability probabilities. Proxima Centauri is a flare star with intense emission of electromagnetic radiation that could strip an atmosphere off the planet.
