We need to talk. You'd better sit down.

According to astronomers at the Mount Lemmon observatory in Arizona, there is an asteroid – they're calling it "2001 AG5" – whose current orbit gives it a one in 625 chance of hitting Earth in 2040. The asteroid is only 460ft wide, not big enough to kill us all, but it could obliterate a city if it lands on one. Further observations will be carried out next year, but at the moment that's where things stand:
 625-1.
 Worried? Should you be?