Actually, using a few calculations on the effects of gravity, it has been determined that either star of Alpha Cen would be able to hold a planet individually as far out as Mars' distance from the sun. So, theoretically there could be a liveable planet there around either. Alpha Cen A is like the sun, but a bit larger, and Alpha Cen B a bit cooler and smaller, but both within the range that could support a life bearing planet, in theory.
Would a planet near either A or B possibly have a circular orbit? Seems like our powerful new adaptive telescopes would be able to resolve such a planet.