Latest from IceCube: Evidence of Cosmic Neutrinos from a Blazar

The IceCube Neutrino Observatory instruments one cubic kilometer of ice deep within the glacier at the South Pole, Antarctica. Completed in 2011, IceCube announced the first detection of cosmic neutrinos in 2013.  These neutrinos, with energies from 10 TeV to beyond 1 PeV, appear to arrive isotropically across the sky, with their origins having remained unknown so far. This summer IceCube presented the first evidence of a cosmic source of such high-energy neutrinos. A rare, high-energy neutrino event detected on 2017 Sept. 22 was reported by IceCube in a public alert that led to extensive follow-up observations across the electromagnetic spectrum. A tantalizing association was found with a flaring blazar, an active galaxy where one of the jets from the central black hole is pointed in our direction. Subsequent analysis of archival IceCube data revealed further evidence that the blazar had a previous episode of neutrino emission. These results may for the first time identify a long-sought accelerator of high-energy cosmic rays.