Huge explosions on Earth may be one-time deals, but their resounding echoes can give us another bang for our buck if conditions are right.
Strangely, the same is true in the depths of space.
Astronomers recently captured a supernova's blinding flash "echoing" off dust 400 light-years from the detonation site in the Large Magellanic Cloud — which means Earthly observers may have seen the original blast 400 years ago. Because a star's death rattle produced the light, scientists can use the new observations to effectively peer into the past.
More: http://www.space.com/scienceastronomy/080421-mm-supernova-forensics.html