Rigil Kentaurus

Alpha Centauri (Rigil Kentaurus) is the closest star system to the Sun at just 4.37 light-years away, located in the constellation Centaurus. The system consists of three stars: Alpha Centauri A (a G2V star very similar to the Sun), Alpha Centauri B (a slightly cooler K1V star), and the red dwarf Proxima Centauri, which at 4.24 light-years is technically the closest individual star. The two main stars orbit each other with a period of about 80 years, with a separation ranging from 11 to 36 AU.

Visible only from latitudes south of about 29°N, Alpha Centauri appears as a brilliant point of magnitude -0.27 (combined light). A small telescope easily splits the pair into two dazzling components (A at mag 0.0, B at mag 1.3) when near maximum separation. Proxima Centauri, a faint magnitude 11 red dwarf, lies over 2 degrees away and requires a telescope and a finder chart. Best observed from March through September from southern latitudes.

Known since antiquity as one of the 'Pointers' to the Southern Cross. Its large proper motion was first measured by Nicolas-Louis de Lacaille in the 1750s. Thomas Henderson determined its parallax in 1832, making it one of the first stars to have its distance measured. In 2016, the discovery of Proxima Centauri b — an Earth-mass planet in the habitable zone — made headlines worldwide.