Gamma rays 10 times more energetic than thought possible detected

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...these discoveries were made using the first observation run using only half of the detection array. Once the rest of the facility comes online, these questions can be probed even more deeply.
The research was published in the journal Nature.

Source: Chinese Academy of Sciences


Beginning to articles from Chinese Academy of Sciences site: kepu.net:

From 2021-04-19
This experiment may solve the "mystery of the century" of the origin of ultra-high-energy cosmic rays
From the introduction:
"Recently, the ASγ experiment in Tibet, China, has observed the highest energy cosmic gamma ray so far, with the highest energy close to 1 PeV (1000 trillion electron volts ) . This is the first time that the electron volt cosmic ray accelerator ( PeVatron ) has been discovered in the Milky Way. Evidence in existence. This achievement is regarded by international colleagues as a milestone in unlocking the "mystery of the century" of the origin of high-energy cosmic rays.
[...]
Credit is given to Cold War time United States - Soviet Union joint forces for starting gamma-ray astronomy.
The high-energy cosmic gamma rays need to pass through the atmosphere when they shoot from space to the earth. At this time, they interact with atomic nuclei in the atmosphere and knock out a variety of new particles. These particles will interact with the atomic nucleus of the atmosphere again during the flight to produce more particles, which are sprayed from the air to the earth like a rainstorm. In this way, the continuous reaction of "two generations, two generations three" will produce new particles, [Ed.: what about new elements? Are Li/Be/B formed by cosmic ray spallation?] just like a big one. As the raindrops fly down, they are scattered into thousands of clusters of small raindrops. Scientists call these small raindrops "showers."
Generally speaking, the higher the energy of cosmic rays, the larger the shower area that reaches the surface.
The ASγ experiment uses the data of ground and underground detector arrays to reduce the background noise of cosmic rays above 100 TeV to one part per million, which greatly improves the sensitivity of gamma-ray detection and becomes the world’s most sensitive to ultra-high energy gamma. The most ray sensitive detector array.​
The ASγ experimental team is composed of Chinese and Japanese scientists. This time, they announced the discovery of an ultra-high energy gamma ray with an energy of 957 TeV . The energy is close to 1 PeV ( 1000 trillion electron volts, 1 followed by 15 zeros). first discovered shot eV cosmic ray accelerator ( PeVatron ) evidence of the Milky Way.​
The result was commented by the American Physical Society as a milestone in the study of the "mystery of the century" of the origin of high-energy cosmic rays.
In addition, China is building a "Large Area High Altitude Cosmic Ray Observation Station" ( LHAASO ) in Daocheng , Sichuan , and its three-quarters array has been completed and put into operation. Compared with the ASγ experiment, the energy range and sensitivity of LHAASO are even higher. It is internationally superior, and it is believed that it will advance the research of cosmic ray physics and ultra-high energy gamma ray astronomy to a new level.​
Some bits are obscured by the translator/translation...



From English Chinese Academy of Sciences site:

From May 17th, 2021
LHAASO Discovers a Dozen PeVatrons and Photons Exceeding 1PeV and Launches Ultra-high-energy Gamma Astronomy Era
China's Large High Altitude Air Shower Observatory (LHAASO)—one of the country's key national science and technology infrastructure facilities—has found a dozen ultra-high-energy (UHE) cosmic accelerators within the Milky Way. It has also detected photons with energies exceeding 1 peta-electron-volt (quadrillion electron-volts or PeV), including one at 1.4 PeV. The latter is the highest energy photon ever observed.
These findings overturn the traditional understanding of the Milky Way and open up an era of UHE gamma astronomy.
These discoveries are published in the journal Nature on May 17. The LHAASO International Collaboration, which is led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences, completed this study.
Photons with energies exceeding 1 PeV were detected in a very active star-forming region in the constellation Cygnus. LHAASO also detected 12 stable gamma ray sources with energies up to about 1 PeV and significances of the photon signals seven standard deviations greater than the surrounding background. These sources are located at positions in our galaxy that can be measured with an accuracy better than 0.3°. They are the brightest Milky Way gamma ray sources in LHAASO's field of view.
Although the accumulated data from the first 11 months of operation only allowed people to observe those sources, all of them emit so-called UHE photons, i.e., gamma rays above 0.1 PeV. The results show that the Milky Way is full of PeVatrons, while the largest accelerator on Earth (LHC at CERN) can only accelerate particles to 0.01 PeV. Scientists have already determined that cosmic ray accelerators in the Milky Way have an energy limit. Until now, the predicted limit was around 0.1 PeV [Ed.: although the The ASγ experiment registered near 1 PeV] thus leading to a natural cut-off of the gamma-ray spectrum above that.

But LHAASO's discovery has increased this “limit,” since the spectra of most sources are not truncated. These findings launch an era for UHE gamma astronomic observation. They show that non-thermal radiation celestials, such as young massive star clusters, supernova remnants, pulsar wind nebulas and so on—represented by Cygnus star-forming regions and the Crab nebula—are the best candidates for finding UHE cosmic rays in the Milky Way.
Through UHE gamma astronomy, a century-old mystery-—the origin of cosmic rays—may soon be solved. LHAASO will prompt scientists to rethink the mechanisms of high energy cosmic ray acceleration and propagation in the Milky Way. It will also allow scientists to explore extreme astrophysical phenomena and their corresponding processes, thus enabling examination of the basic laws of physics under extreme conditions.
I'll leave off here before re-posting the whole article. The energetics here seem to be a big deal: 10x0.1PeV=~1PeV; one measurement at 1.4PeV is 14x what was the predicted maximum.
This seems like big news.
 
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