A joint team of Chinese and international researchers released new results Sunday from the Large High Altitude Air Shower Observatory (LHAASO) in Daocheng County, Sichuan Province, pinpointing the likely origin of the cosmic ray "knee," a sharp drop in the cosmic ray energy spectrum above 3 peta-electronvolts (PeV) discovered nearly 70 years ago [1].
The team published two studies in National Science Review and Science Bulletin linking micro-quasars driven by accretion onto black hole systems as the probable source of this cosmic ray energy feature [1]. LHAASO systematically detected ultra-high-energy gamma rays from five micro-quasars for the first time, marking a milestone in understanding these powerful galactic accelerators [1].
This advance relied on LHAASO's multiparameter measurement techniques, which the researchers used to obtain a large statistical sample of high-purity protons, helping to clarify the composition of cosmic rays near the knee energy threshold [1].
Aerial drone photographs taken October 28, 2025, showed the extensive LHAASO facility that enabled these observations [1]. The key findings were published online in November 2025 and publicly announced this Sunday [1].
The identification of micro-quasars as sources of the cosmic ray knee resolves a decades-old mystery in astrophysics by connecting this spectral feature with specific astronomical objects emitting ultra-high-energy particles.
The research represents a significant step in unraveling the origins of cosmic rays at energies above 3 PeV, with detailed observational evidence linking particle acceleration in black hole binary systems to features in cosmic ray spectra observed at Earth.
