About half the stars in the sky are part of a binary system – two stars orbiting one another. It is possible that if a small star came close to our sun (which is also small in comparison to most stars), it would form a stable binary system. If however, this small star collided with the sun, this would destroy life on Earth due to the gamma ray explosion caused by this event. This is however, extremely unlikely! Some binary star systems can become unstable and merge with one another, a process which isn’t well understood.