High-speed neutrinos detected by the IceCube observatory at the South Pole do come from distant cosmic sources such as galactic nuclei, after all.
Neutrinos are subatomic particles that come in three 'flavours' — electron, muon and tau — which change as they travel over long distances. Previous IceCube data suggested that few muon or tau types had been detected in 2010–12, indicating a possible non-cosmic source or exotic new physics affecting how neutrinos oscillate.
Gary Binder of the University of California, Berkeley, and his colleagues identified 137 high-energy neutrinos in this date range. They ruled out mainly electron and mainly muon scenarios, concluding that the ratio of flavours is consistent with 1:1:1. This is the expected ratio from neutrinos oscillating over long distances, and further confirms that they originated from distant astrophysical objects.
A separate study by Francesco Vissani at the Gran Sasso Science Institute in L'Aquila, Italy, and his colleagues looked at higher-energy neutrinos detected by IceCube (pictured is one of the sensors in the ice) and also concluded that these are likely to be from cosmic sources.
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IceCube gives neutrinos flavour. Nature 521, 9 (2015). https://doi.org/10.1038/521009e