3Q: Janet Conrad on the first detection of a neutrino’s cosmic source
For the first time, scientists from around the world have detected a source of high-energy cosmic neutrinos — subatomic particles, produced in the aftermath of explosive astrophysical phenoma, that streak across the universe by the billions, leaving very little trace of their presence. Neutrinos, Italian for “little neutral ones,” are often described as “ghost particles,” for their extremely weak interactions with ordinary matter. Indeed, billions of neutrinos stream through our fingernails every second, without ruffling so much as a molecule of matter. And yet, on Sept. 22, 2017, the IceCube Neutrino Observatory, based at the Amundsen-Scott South Pole Station, detected a neutrino in signals picked up by its detectors buried deep in the Antarctic ice. Researchers there quickly sent out alerts to ground- and space-based telescopes in hopes of finding the neutrino’s cosmic source. An answer was soon confirmed: The neutrino originated from a blazar — an active galaxy with a...