LHASA, March 16 (Xinhua) -- A high-altitude cosmic ray observatory in southwest China's Xizang Autonomous Region has provided scientists with an unprecedented look at the invisible forces governing our galaxy.
The Tibet ASγ experiment has successfully measured chaotic magnetic turbulence on a very small scale in space for the first time, revealing new details about how cosmic rays travel through the Milky Way.
The findings, recently published in the journal Science Advances, focus on Geminga, a dead star -- known as a pulsar -- located about 800 light-years from Earth.
Using a massive detector array at Yangbajing in Xizang, the international team of Chinese and Japanese scientists studied a halo of high-energy light surrounding this pulsar. They achieved this by observing gamma rays with energies exceeding 100 tera-electron volts (TeV) -- far more powerful than anything produced by human-made particle accelerators.
"The research provides the first direct evidence that the Geminga pulsar wind nebula accelerates electrons only up to a specific energy limit of about 100 TeV," said Huang Jing, a professor from the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences.
Moreover, the team measured how these particles spread into space. They discovered that in the region around the Geminga halo, particle diffusion is surprisingly slow. Cosmic rays are moving through this area with only about one percent of the efficiency they have in the rest of the galaxy. It is as if the particles are encountering a cosmic "speed bump" or a thick fog that slows their escape.
Moreover, for the first time, scientists were able to measure the turbulence of magnetic fields on incredibly small scales -- less than a single parsec (about 3.3 light-years). They found that this turbulence follows a specific pattern, known as Kolmogorov-type scaling, which is similar to how energy moves in a stirred cup of coffee or in atmospheric weather patterns.
"This is the first experimental confirmation that such magnetic turbulence exists on such tiny scales in space," said Huang.
The findings are a major step forward in understanding cosmic rays. By studying how they are trapped and slowed around objects like Geminga, scientists can better understand the complex "weather" of space and the magnetic fields that shape our galactic neighborhood, said Bi Xiaojun, a professor from the IHEP.
The Tibet ASγ experiment, located 4,300 meters above sea level in Xizang's Yangbajing Town, has been operating since 1990. Its unique underground detectors block out 99.92 percent of unwanted background noise.
"The success of this observation opens new doors for understanding cosmic-ray propagation and magnetic-field dynamics in the universe. The findings are expected to have far-reaching implications for future multi-messenger and high-energy gamma-ray studies," said Fang Kun, an expert from IHEP. ■
