Trinary star

A trinary star is a star system consisting of three stars. In most cases are gravitationaly bound -- two of the stars orbit their mutual center of mass as a binary star, and the third star and binary pair orbit each other around their center of mass. Alternatively, on relatively rare occasions, one of the stars is not bound to the others but instead is an independent star that happens to be passing extraordinarily close to a binary (in the course of their motion around the galactic center).

Known Trinary Systems

 * Alpha Centauri system