The night sky in neutrino light resembles a canvas worked on by two hands. One holds a broad, soft brush: these are supernova remnants, the shells left behind after stellar explosions. The other grips a fine, hard pen — microquasars, binary systems where a black hole twists matter into narrow jets. Both hands accelerate protons to enormous energies, and those protons, colliding with interstellar gas, give birth to neutrinos and gamma rays. But until now, it was unclear which hand was responsible for which part of the sky.

The authors of the new work built a model in which the two classes of accelerators act independently. For each source, they calculated how particles spread through the Galaxy, like ink on paper. Supernova remnants accelerate protons up to 68 TeV, while microquasars reach 6 PeV, a hundred times more energetic. The acceleration efficiency was tuned so that the model matches cosmic-ray measurements at Earth. It turns out that microquasars convert about 10% of their energy into accelerated particles, and supernova remnants, 6%.

Comparison with data from the IceCube neutrino observatory shows agreement: the predicted flux in the inner Galaxy matches observations over 12 years. Gamma-ray maps, calculated with absorption on background radiation, also reproduce LHAASO measurements. The hot spots on the neutrino sky turned out to be not individual accelerators, but regions of dense gas onto which a sea of cosmic rays is projected.

Astronomers now have a ready-made background template. It will help in searching for point-like neutrino sources in IceCube, KM3NeT, and Baikal-GVD data, separating them from the diffuse glow. Moreover, the model connects local cosmic-ray measurements with the global emission of the Galaxy — two hands painting one sky are finally distinguishable by their strokes.