A picture of the Crab Nebula Photo: VCG

Chinese and Japanese scientists for the first time discovered gamma rays with energy beyond 100 teraelectron volts (TeV) from an astrophysical source. 

A gamma ray is a type of cosmic ray generated by intense activities of high-energy celestial bodies related to origins of the universe, evolution of stars and the space environment, according to a pamphlet the Global Times reporter obtained from the Chinese Academy of Sciences.

Scientists in a joint China-Japan experiment in Southwest China's Tibet Autonomous Region discovered 24 gamma rays of energy above 100 TeV, with the highest figure reaching 450 TeV - more than five times higher than the 75 TeV rays previously detected by the High-Energy-Gamma-Ray Astronomy Cherenkov telescope in Germany, Huang Jing, the team's spokesperson, said at a press conference on Wednesday in Beijing.

According to the Xinhua News Agency, 450 TeV is equivalent to 45 billion times the energy of X-rays for medical use.

"Before this discovery, many scientists believed that photons could not be accelerated to energy higher than 100 TeV," Huang said.

The discovery will lead scientists one step closer to the origins of cosmic rays and the universe, Chen Yang, a professor at the school of astronomy and space sciences of Nanjing University, told the Global Times on Wednesday.

The origin of cosmic rays has been a mystery since their discovery in 1912. 

The gamma rays are electrically neutral, and can avoid influence from magnetic fields and maintain a straight line in space, thus allowing us to better explore the origins of these rays, according to Chen. 

Experts said at the conference that cosmic rays are one of the obstacles to astronauts when they live and work. Thus, research on newly discovered rays would also help scientists to develop protection tools to better help astronauts avoid radiation from cosmic rays.

Experts believe that the gamma rays come from the Crab Nebula, which is a supernova remnant in the constellation Taurus and is about 6,500 light years away from Earth. 

The Crab Nebula was produced by a supernova explosion, which was recorded in 1054 in official historical documents of the Northern Song Dynasty (960-1127).

In 1969, scientists discovered a pulsar, rotating 30 times per second, embedded in the nebula. In the modern era, the Crab Nebula has been observed at all electromagnetic wavelengths ranging from radio to very high energy gamma rays.

The Tibet ASgamma experiment, located in Yangbajing at an altitude of 4,300 meters, was jointly launched in 1990 by China and Japan. 

Experts said that Tibet is ideal for research about rays from outer space because of its high altitude.

To catch gamma rays with high energy, experts put a new detector 2.5 meters underground in 2014 to rule out 99.92 percent of non-gamma rays, significantly improving the sensitivity.
Newspaper headline: Highest-energy gamma rays detected