Highest Ever Energy Light Captured By Chinese Mountain Observatory

sciencehabit writes: Using an observatory on the edge of the Tibetan Plateau, astronomers have spotted the highest energy light ever, gamma ray photons up to 1.4 petaelectronvolts (PeV). They have traced these extreme photons back to a dozen of their likely sources: powerful factories in the Milky Way Galaxy that accelerate charged particles called cosmic rays. The results are challenging theorists' understanding of what these factories are and how they generate such high-energy light. 'The findings are extremely important and impressive,' says Petra Huentemeyer, an astrophysicist at Michigan Technological University and spokesperson for a rival gamma ray telescope, the High-Altitude Water Cherenkov Observatory (HAWC) in Mexico. 'It's a giant leap toward finally understanding the origin of the highest energy cosmic rays.'

Discovered more than 100 years ago, cosmic rays are charged particles, including protons and other atomic nuclei, that have been accelerated nearly to the speed of light. Their sources are poorly understood because interstellar magnetic fields bend them on their path to Earth. However, as cosmic rays rocket away from their sources, they also emit photons, usually about one-tenth as energetic as the cosmic rays themselves, that follow a straight path to Earth. Although Earth's atmosphere blocks this gamma ray light, when the photons slam into air molecules, they create showers of secondary particles and faint blue Cherenkov light that astronomers can look for. China's Large High Altitude Air Shower Observatory (LHAASO) aims to catch the air showers associated with the highest energy gamma rays, which in turn correspond to the highest energy cosmic rays.

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