Precise measurements of the cosmic ray proton energy spectrum in the “knee” region
Ultrahigh-energy gamma-ray emission associated with black hole-jet systems
At over 4,400 meters above sea level on the Qinghai-Xizang Plateau in Daocheng, southwest China's Sichuan Province, stands the world's most advanced cosmic-ray observatory – the Large High Altitude Air Shower Observatory (LHAASO). Since its completion in 2021, it remains the world's highest, largest and most sensitive observatory for detecting high-energy cosmic rays and gamma rays.
What mechanism accelerates cosmic rays to the 3 peta-electron-volt (PeV) range — over 1,000 times the energy of the world's most powerful man-made particle accelerators — causing a sharp decline in the number of higher-energy cosmic rays and forming a knee-like shape in their energy spectrum? Using data from China's Large High Altitude Air Shower Observatory (LHAASO), a team of Chinese and international scientists has identified powerful jets from black holes as the "engines" driving high-energy particles in the Milky Way. This marks a milestone in observationally connecting the "knee" structure to a specific type of astrophysical source since its discovery 70 years ago.
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