a binary star, the brightest star in the constellation Centaurus: magnitude, -0.27: it is the nearest of the stars that are visible to the naked eye, except for the sun
See Alpha Centauri in American Heritage Dictionary 4
(ălˈfə sĕn-tôrˈē)
noun
A multiple star in Centaurus whose three components represent the brightest object in the constellation, 4.4 light-years from Earth.