Alpha Centauri A has 1. 1 times the mass and 1. 519 times the luminosity of the Sun, while Alpha Centauri B is smaller and cooler, at 0. 907 times the Sun's mass and 0. 445 times its luminosity. The pair orbit around a common centre with an orbital period of 79. 91 years. Their elliptical orbit is eccentric, so that the distance between A and B varies from 35. 6 AU (astronomical units), or about the distance between Pluto and the Sun, to 11. 2 AU, or about the distance between Saturn and the Sun.