Japanese team confirms Milky Way object accelerating protons past one peta-electron-volt

An international collaboration headed by associate professor Tsunefumi Mizuno of Hiroshima University has identified the Galactic source LHAASO J1912+1014u as a proton PeVatron capable of energizing protons beyond one peta-electron-volt. The object, situated near Altair in the constellation Aquila, was examined using observations from the Tibet AS-γ and LHAASO gamma-ray arrays, NASA’s Fermi-LAT, Japan’s FUGIN radio survey, and Chandra’s X-ray telescope.

Combined measurements reveal a smooth gamma-ray spectrum extending from over 100 TeV down to 400 MeV, a spatial correlation between GeV gamma rays and interstellar gas, and only faint diffuse X-ray emission—signatures that favor proton over electron acceleration. The study, appearing in The Astrophysical Journal, also characterizes the accelerated particles and notes many similar Galactic candidates await confirmation.

Co-authors Naoto Nakahara, Hidetoshi Sano, Takeru Murase, Tomohiko Oka and Hiromasa Suzuki contributed from Gifu University, Julius-Maximilians-Universität Würzburg and Miyazaki University. This discovery advances knowledge of the origins of the Milky Way’s highest-energy cosmic rays.