: The IceCube
detector at the South Pole found evidence of two 1-PeV neutrinos earlier this year
. IceCube uses 2-km-deep holes lined with photodetectors to look for flashes of light caused when high-energy particles strike water molecules in the ice. The researchers running the detector have examined more of the data collected and, by ruling out additional background events, were able to expand the detector's sensitivity down to 30 TeV. The increased sensitivity revealed 26 more high-energy neutrinos with energies ranging from 30 TeV to 1 PeV. Seven of the neutrino collisions released muons, which suggests that the neutrinos were muon neutrinos. The other collisions created sprays of particles so it isn't clear what flavor
of neutrino they were. Because they are so much more energetic than neutrinos in cosmic rays, it is likely that the neutrinos were produced outside of the solar system.