In our corner of the galaxy, inside a bubble of thin, hot gas, a star exploded 30,000 years ago. The echo of that blast, a stream of fast particles, is still flying toward us and mixing with the general flow from distant parts of the galaxy.

It used to be thought that particles from space arrive uniformly from all directions, like light from many distant lamps. But measurements showed that as particle energy rises, the flux becomes more and more uneven, and the number of particles at 200 GeV suddenly starts growing faster, while above 50 TeV it starts to drop. Standard models couldn't explain this.

Now both oddities have an explanation. The nearby explosion adds its particles to the general background, making the flux harder at 200 GeV. And above 50 TeV, the particles from the explosion run out: it's still too young to have accelerated them to such energies. Future precise measurements will show whether this picture is correct, but already it's clear: our cosmic neighborhood isn't as calm as it seemed.