We are only 150 light years away from HR 8210 at present - well short of the 160 to 200 light years thought to be the minimum safe distance from a supernova. If it did let fly, the high-energy electromagnetic radiation and cosmic rays it released would destroy Earth's ozone layer within minutes, giving life little chance of survival. "The fact that there's such a system so close to us suggests maybe these objects are not so rare," says Latham.