What is known by scientists as ‘giant leap',a Tibetan astronomical observatory has detected light particles up to 1.4 Peta electron volts, which is more than 1000 trillion times the average energy of a sunlight particle. These newly detected photons, which are the highest-energy particles ever seen in the universe, are 1000 times stronger than what astronomers expected to find. High-energy charged particles, also known as cosmic rays, are protons and atomic nuclei which have been accelerated to near the speed of light. These rays emit from violent astronomical events -such as supernovae -final explosions of dying stars when new stars are born. However, scientists are often unable to understand their sources well, as such big astronomical events create strong electromagnetic fields that bend the path of these rays.
Cosmic rays were discovered 100 years ago and since then, scientists have been trying to trace their sources. When they travel, they also emit photons one-tenth as energetic as them. These photons, also known as gamma rays, travel to Earth in a straight path and blocked by our atmosphere. However, when these gamma rays interact with air molecules, they create rains of secondary particles. The Large High Altitude Air Shower Observatory (LHAASO) in Tibet is deployed to catch such particles containing high energies.
Using data from the Chinese observatory’s first year of observation in 2019, researchers detected more than 530 photons with energies higher than 0.1PeV, according to the study published on May 17 in Nature. These photons were traced to 12 sources in our galaxy capable of such high accelerations in PeVs.
The source of the highest energy particles is suspected to be the Cygnus Cocoon, a nursery of stars 4600 light-years away from the sun. The sources of these high-energy lights are termed as PeVatrons because they emit particles with energies in PeVs. “PeVatrons are basically everywhere in our galaxy,” Zhen Cao, one of the astrophysicists who conducted the study, said in a statement to the Science magazine.
According to Cao, models have predicted that the magnetic fields in the Crab Nebula, a high-energy supernova explosion in the Milky Way and another suspected source of the detected photons, could excite particles to energies as high as 0.1 PeV. However,to touch the 1 PeV mark, all the parameters have to be pushed to the extreme.