Binary star system planet, artwork. Small, rocky planet that has formed in a binary star system. The two stars forming this binary star system are at top right and bottom left. This planet orbits one of the stars, and the planet and its parent star both orbit the other star. A large proportion of stars are thought to be members of binary star systems. The different colours of the stars can indicate their age, mass and composition. Blue stars can be large high-mass stars, and yellow stars can be lower-mass Sun-like stars. The craters on this planet shows that it is small and does not have an atmosphere.