How cosmic rays are actually distributed across the Milky Way

Cosmic rays pervade the galaxy but their spatial distribution remains poorly mapped. Researchers used a decade of Fermi telescope observations of gamma rays—the smoking gun of cosmic rays hitting gas—to reconstruct a 3D model of cosmic-ray proton density throughout the Milky Way. The map reveals a modest enhancement toward the galactic center and matches measurements taken near Earth, suggesting the reconstruction captures real physics rather than artifacts.