How far away is Alpha Centauri from Earth?
Proxima Centauri, the closest star in the Alpha Centauri system, is 4.2465 light-years (1.3020 parsecs) from the Sun. The two main stars, Alpha Centauri A and B, are slightly farther at 4.344 light-years.
Questions about Alpha Centauri
Short answers, pulled from the story.
How many stars make up the Alpha Centauri system?
Alpha Centauri consists of three stars: Rigil Kentaurus (Alpha Centauri A), Toliman (Alpha Centauri B), and Proxima Centauri (Alpha Centauri C). Rigil Kentaurus and Toliman form a gravitationally bound binary pair, while Proxima Centauri orbits the pair with a period of approximately 511,000 years.
Does Proxima Centauri have any confirmed planets?
Proxima Centauri has two confirmed planets. Proxima Centauri b, discovered in 2016 by astronomers at the European Southern Observatory, is an Earth-sized world in the star's habitable zone with a minimum mass of 1.17 Earth masses. Proxima Centauri d, a sub-Earth in a very close orbit, was detected in 2022 and confirmed in 2025.
Who discovered that Alpha Centauri is a binary star?
Jean Richaud recognized the binary nature of Alpha Centauri AB in December 1689 while observing a passing comet from his station in Puducherry. It was only the third binary star ever discovered, after Mizar AB and Acrux.
Who discovered Proxima Centauri and when?
Robert T.A. Innes discovered Proxima Centauri in 1915 by comparing photographic plates taken at different times during a proper motion survey. He identified it as the closest star to the Sun yet found and proposed naming it Proxima Centaurus.
How bright is Alpha Centauri in the night sky?
Alpha Centauri AB has a combined apparent magnitude of -0.27, making it the third-brightest star in the night sky, outshone only by Sirius and Canopus. When counted as an individual star, Rigil Kentaurus alone has an apparent magnitude of +0.01, ranking it fourth-brightest.