Binary, BY nuhr ee, star or double star, is a pair of stars that are close together and cannot escape from each other. The stars hold each other captive by the force of gravity, and each one orbits around the other. The individual members of a few binaries can be seen without a telescope. But the stars in most binaries are so close together that they look like single stars. The binary star nearest earth looks like a single star. It belongs to the triple-star system Alpha Centauri, 4.3 light-years from earth (see Alpha Centauri).