The Milky Way shines in high-energy neutrinos

The most energetic astrophysical sources in the Milky Way, cosmic accelerators capable of producing high-energy cosmic rays, have resisted discovery for over a century. Up to now, astrophysicists sought these sources mainly by scouring the Galaxy for the gamma rays they are expected to emit. In 2023, the IceCube Neutrino Observatory discovered high-energy neutrinos from the Milky Way, inaugurating a tell-tale stream of evidence of cosmic-ray production and interaction in the Galaxy.

Key advances

• In 2023, the IceCube Neutrino Observatory discovered the first high-energy neutrinos coming from the Milky Way, most of them with energies in the range of 1–100 TeV.

• The neutrinos were discovered in the form of a diffuse flux from the Galactic plane, whose spatial distribution matches that of previously detected gamma rays from the Milky Way.

• The flux of high-energy neutrinos from the Galactic plane constitutes 6–13% of the all-sky high-energy neutrino flux first discovered by IceCube in 2013.

• The discovery of high-energy Galactic neutrinos points to the long-predicted existence of PeVatrons in the Milky Way — astrophysical accelerators of cosmic rays up to PeV-scale energies — though none have been found yet.