Binary asteroid 90 Antiope, computer artwork. This pair of asteroids orbits in the main part of the outer asteroid belt. Each asteroid is about 86 km across, orbiting its partner from a distance of 170 km and with a period of 16.5 hours. Binary asteroids are thought to be quite common, being created during collisions between asteroids. The 90 Antiope asteroids orbit the Sun (upper left) at a distance of around 545 to 398 million kilometres, several times the Earth-Sun distance.