Proxima

Proxima Centauri, commonly referred to as Proxima, is the nearest known star to the Sun. It lies in the Alpha Centauri star system at a distance of about 4.24 light-years and is classified as a red dwarf of spectral type M5.5V. The star was identified in 1915 by Robert Innes and is named Proxima because it is the closest star to the Sun. As part of a wide triple-star system with Alpha Centauri A and B, Proxima is bound to the pair and orbits them on a long, gradual path.

Proxima Centauri has a very low mass and luminosity, typical of red dwarfs. Its mass is about 0.12 solar masses, radius around 0.15 solar radii, and luminosity roughly 0.0017 times that of the Sun. Its surface temperature is near 3,040 kelvin. The star is magnetically active and prone to stellar flares, which can cause rapid increases in ultraviolet and X-ray radiation.

The planetary system of Proxima Centauri includes at least one confirmed exoplanet, Proxima b, discovered in 2016 by radial-velocity measurements with the HARPS instrument. Proxima b has a minimum mass close to Earth's and orbits Proxima every about 11.2 days at a distance of roughly 0.05 AU. Some models place Proxima b in or near the star’s habitable zone, but habitability remains uncertain due to the star’s variability and high-energy radiation. Additional planetary signals have been proposed (as candidates) but have not yet been confirmed.

Proxima Centauri’s proximity makes it a prime target for future observations and interstellar exploration concepts. It is the focus of studies on exoplanet habitability around red dwarfs and has featured in proposals such as Breakthrough Starshot for potential interstellar probes.