Asteroid 2010 SO16 and the Earth follow similar orbits around the Sun. But as seen from Earth, 2010 SO16 gradually traces out a horseshoe shape in space, taking 175 years to go from one end of the horseshoe to the other. In this schematic animation covering 100 years around the present, with the Sun [S] at the centre, the asteroid [diamond] approaches Earth [E] and then recedes from it. Credit: Armagh Observatory