Chinese scientists have detected a dozen ultra-high-energy (UHE) cosmic accelerators within the Milky Way, a find that could overturn humanity's understanding of the galaxy. It could help reveal the origin of cosmic rays, which have puzzled scientists for a century.
The findings were based on the observations of China's Large High Altitude Air Shower Observatory (LHAASO), one of the country's key national science and technology infrastructure facilities, which is under construction in Daocheng in southwest China's Sichuan Province.
These discoveries were published in the journal Nature on June 3, 2021.
Scientists led by the Institute of High Energy Physics (IHEP) under the Chinese Academy of Sciences made the discoveries after an 11-month observation period using the completed half of the installation.
Scientists have also detected photons with energies exceeding 1 Peta-electron volt (quadrillion electron-volts or PeV), 100 times more than the record high achieved by any manmade accelerator on Earth. One photon with an energy of 1.4 PeV was detected, the highest value ever observed by humans.
These findings overturn our traditional understanding of the Milky Way and open up an era of UHE gamma astronomy. These observations will prompt us to rethink the mechanism by which high-energy particles are generated and propagated in the Milky Way.
Through UHE gamma astronomy, the century-old mystery of the origin of cosmic rays may soon be solved.
LHAASO has revealed many PeV cosmic acceleration sources in the Milky Way, all of which are candidates for being UHE cosmic ray generators. It is a crucial step toward determining the origin of cosmic rays, according to Chen Songzhan, the physics coordinator of LHAASO Collaboration.
Photons with energies exceeding 1 PeV were detected in a very active star-forming region in the constellation Cygnus.
The star-forming area in the direction of Cygnus is the brightest region in the northern territory of the Milky Way, with many massive star clusters. Massive stars only exist for about one million years, so the clusters contain enormous stars in the process of birth and death, with a complex, strong-shock environment. They are ideal "particle astrophysics laboratories," or places for accelerating cosmic rays.
The first PeV photons found by LHAASO were from the star-forming area of the constellation Cygnus, making this area the best candidate for exploring the origin of UHE cosmic rays. Therefore, much attention has turned to LHAASO and multi-wavelength observation of this region, which could offer a potential breakthrough in solving the "mystery of the century".