Astrophysical neutrinos: IceCube highlights

The IceCube Neutrino Observatory features approximately a cubic-kilometer volume of instrumented ice at the geographic South Pole. A high energy astrophysical neutrino flux has been observed, initially in 2013, as an excess of neutrinos above 10 TeV compared to the expectation from an atmospheric neutrino background. This signal, nowadays significant at >6 σ, has been observed both in neutrino interactions starting in the detector volume and in throughgoing muons generated in charged-current muon neutrino interactions outside the detector. No astrophysical objects have yet been identified as the flux source, which is currently consistent with an isotropic expectation. This paper reviews the evidence for the astrophysical flux and the status of the search for its sources. It also presents a discussion of proposed detector extensions being designed to solve the mystery of the astrophysical neutrino origin.