Astronomers have conclusively identified a source of the highest-energy cosmic ray protons in the Milky Way, confirming the existence of a natural particle accelerator near the star Altair that operates at energies roughly a thousand times beyond what humanity's Large Hadron Collider can produce.
The object, designated LHAASO J1912+1014u, was first flagged in 2024 by ground-based observatories in Tibet and China after researchers detected gamma rays streaming from it at exceptionally high energies. However, the original observations could not determine whether the gamma rays came from protons or fast-moving electrons, leaving the question unresolved. [1]
An international team led by Tsunefumi Mizuno of Hiroshima University solved the problem by combining data from three separate instruments. NASA's Fermi telescope supplied gamma-ray observations, Japan's FUGIN survey provided radio data tracing interstellar gas nearby, and NASA's Chandra Observatory contributed X-ray measurements. Together the three data sets showed that the gamma-ray emission stretched smoothly across a vast energy range in a way that ruled out electrons as the source, confirming protons slamming into surrounding gas at energies exceeding one quadrillion electron volts. [2]