An accelerator of the highest-energy cosmic-ray protons in our galaxy has been conclusively identified: LHAASO J1912+1014u, a source in the constellation Aquila near the bright star Altair, is a 'proton PeVatron' that pushes protons past one quadrillion (10^15) electron volts — beyond the energy of any human-built accelerator.
An international team led by Hiroshima University confirmed the finding by combining observations from three major facilities: NASA's Fermi Gamma-ray Space Telescope, the FOREST/FUGIN survey with the Nobeyama 45-m radio telescope, and NASA's Chandra X-ray Observatory — layered on TeV data from China's LHAASO and the Japan–China Tibet AS-gamma experiment. The study was published on 16 July 2026 in The Astrophysical Journal.
Discovered in 2024 and initially thought to be a supernova remnant, the source gained attention when emissions above 100 trillion electron volts (TeV) were detected. To prove it accelerates protons rather than electrons, the team showed that its gamma-ray emission extends smoothly from over 100 TeV down to 400 million electron volts — hard to explain with electrons — that the GeV gamma-ray map matches the distribution of interstellar gas, and that diffuse X-ray emission is very weak.
'Finding a cosmic-ray proton accelerator above that PeV level is one of the most exciting topics in modern astrophysics, and we identified one such object,' said Tsunefumi Mizuno of Hiroshima University, first author of the study. Dozens of other PeVatron candidates remain, and the team plans to examine them next.
