LHAASO has traced the mysterious cosmic ray “knee” to powerful micro-quasars firing ultra-energetic particles across the galaxy. LHAASO has uncovered that micro-quasars, black holes feeding on companion stars, are powerful PeV particle accelerators. Their jets produce ultra-high-energy gamma rays and protons that exceed long-held expectations. Precise cosmic-ray measurements reveal a new high-energy component, suggesting multiple sources within the Milky Way. These findings finally tie the “knee” structure to black hole jet systems.

Milestone results released by the Large High Altitude Air Shower Observatory (LHAASO) on November 16 have finally clarified a decades-old puzzle in astrophysics: the unusual drop in cosmic ray counts above 3 PeV that produces what scientists call the “knee” in the cosmic ray energy spectrum.

The cause of this steep decline has remained mysterious since it was first identified nearly 70 years ago. Researchers long suspected that the feature reflects the highest energies that cosmic ray sources can reach, marking a shift in the spectrum from one power-law behavior to another.