(astronomy) The brightest star in the southern constellation of Centaurus. Alpha Centauri is actually a binary star with Proxima Centauri as a third component. Alpha Centauri B is less bright than Alpha Centauri A and is somewhat less bright than our sun.
Wiktionary
Origin of Alpha-centauri-b
From α (brightest) + Centauri ("of the constellation Centaurus")
