A single, high-energy neutrino struck Earth on Sept. 22, 2017. It came from a distant galaxy, wrapped around a supermassive black hole. And, beginning with a blockbuster paper published today (July 12) in the journal Science and signed by hundreds of scientists spread across dozens of laboratories, it's leading giddy astrophysicists to rewrite their models of the universe.
That's because, for the first time, this high-energy neutrino, a ghostly particle that barely interacts with other matter, left enough clues for them to figure out where it came from.
For 4 billion years, this neutrino soared through space undisturbed. It might have passed stars, chunks of rock, or other galaxies. It might even have passed through them; neutrinos can usually stream through matter without leaving any trace. So, for most of the time it took life on Earth to emerge, to form bacteria, fungi, plants and animals, and for one of those animals (us) to discover their existence, this neutrino traveled undisturbed.
Then it crashed into an atom in a block of ice in Antarctica, spat another high-energy particle called a muon into the IceCube Neutrino Observatory, a massive particle detector buried under the Antarctic ice, and it disappeared forever.
What is neutrino ?
