For a long time there have been something of a mystery where the most energetic high energy particles originates. It have been suspected that supernova explosions were involved somehow, but other explanations have been suggested including they were somehow produced by our own galaxy or more outlandish, such as that they might have originated elsewhere than our own galaxy.
But the cosmic rays sometimes had energies even higher than what a supernova would be able to produce.
Or to put in other words, we knew about the bullet but lacked the weapon for our investigation.
Now we might have one explanation that tells us it was the butler after all.... sorry make that supernova.
Read the article at Spaceflight now website by conveniently clicking on this sentence.