Most stars in the galaxy are not alone, but belong to binary systems. This pair is composed of a white star, bigger and hotter than our Sun, and a companion that recently started to accrete mass from its neighbor. In a binary system it’s difficult for a planet to settle in a stable orbit – but several such planets have been discovered in the last few years, some of them even in the habitable zone of the system.
Mass transfer between two neighboring stars can drastically alter the destiny of a star system.