In theory, a supernova thousands of light-years away could release gamma-rays that would fry most life on Earth. But the star must be positioned exactly right for this to ever happen, and there's no way to prove it. Until now.
In the ultimate cosmic cataclysm, two ultra-dense bodies collide. For less than a second, incredible amounts of super-charged particles explode forth. These blasts could wipe out most life on Earth...and it's probably happened dozens of times already.
We recently discovered that gigantic gamma ray bubbles were balanced above and below the center of the Milky Way, stretching out 25,000 light-years in each direction. And now we might finally know where these mysterious bubbles come from.