The Alpha Centauri system is actually a group of three stars: Proxima Centauri,
and Alpha Centauri A and B. Proxima Centauri is the dimmest of the three, and 
is actually the closest star to the Earth.  Alpha Centauri A and B are a close 
binary pair. The Alpha Centauri system is at a distance of about 4.3 
light years from the Earth.

Credit: MSX/IPAC/NASA