A new study shows how a 200-metre-wide cluster of rocks, first spotted by scientists in 2011, could have spawned the Chelyabinsk meteor which exploded over Russia earlier this year.

If correct, that means we may need to watch out for further impacts from other fragments of the cluster, which are still at large, in orbit around the sun.

The meteor that exploded over Russia on 15 February, scattering debris across the Chelyabinsk region and injuring hundreds , came as a complete surprise. Since then researchers have traced it to the Apollo asteroid family, but no one had matched it to a particular member of the group.