Proxima Centauri b
Artist's conception of Proxima Centauri b as a terrestrial exoplanet, with Proxima Centauri and the Alpha Centauri system visible in the background. The actual appearance and composition of the exoplanet beyond this data is currently unknown. | |
| Discovery | |
|---|---|
| Discovered by | Anglada-Escudé et al. |
| Discovery site | European Southern Observatory |
| Discovery date | 24 August 2016 |
| Doppler spectroscopy | |
| Orbital characteristics | |
| 0.04856±0.00030 AU | |
| Eccentricity | 0.02+0.04 −0.02 |
| 11.1868+0.0029 −0.0031 d | |
| 3.3+1.8 −2.3 radians | |
| Semi-amplitude | 1.24 ± 0.07 m/s |
| Star | Proxima Centauri |
| Physical characteristics | |
| 0.94–1.4 R🜨 | |
| Mass | ≥1.07±0.06 M🜨 |
| Temperature | Teq: 234 K (−39 °C; −38 °F) |
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 0.04856 AU (7.264 million km; 4.514 million mi) with an orbital period of approximately 11.2 Earth days. Its other properties are only poorly understood as of 2025, but it is potentially a terrestrial planet with a minimum mass of 1.07 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.
Announced on 24 August 2016 by the European Southern Observatory (ESO), Proxima Centauri b was confirmed via several years of Doppler spectroscopy measurements of its parent star. The detection of Proxima Centauri b was a major discovery in planetology, and has drawn interest to the Alpha Centauri star system as a whole. As of 2023, Proxima Centauri b is believed to be the best-known exoplanet to the general public. The exoplanet's proximity to Earth offers an opportunity for robotic space exploration.