Below the geographic South Pole, the IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrino detector. IceCube detects more than 100,000 neutrinos per year in the GeV to 10 PeV energy range. From those, we have isolated a flux of high-energy neutrinos of cosmic origin, with an energy flux that is comparable to that of high-energy photons. We have also identified the first cosmic accelerators pinpointing the dense cores of active galaxies, powered by supermassive black holes, as sources of cosmic neutrinos (and cosmic rays!).
We will review neutrino astronomy, its present and future telescopes, and the recent progress in measuring the cosmic neutrino spectrum and in identifying its origin.