NANJING, April 30 (Xinhua) -- The international collaboration of the Dark Matter Particle Explorer (DAMPE) satellite on Thursday announced its latest findings, reporting for the first time the observation of the charge-dependent limit of cosmic ray acceleration, and providing key evidence for the existence of a "super particle accelerator" near the Earth.
The study has been published online in the academic journal Nature.
Cosmic rays, consisting of high-energy particles such as various atomic nuclei, electrons and positrons, gamma rays and neutrinos -- traveling at speeds close to that of light -- remain largely enigmatic. Physicists are still pondering where they come from and how they can be accelerated to ultra-high energies.
Believed to be associated with celestial bodies such as supernova remnants, rapidly rotating neutron stars, and accreting black holes, cosmic rays carry important scientific information about the universe. To unravel the mysteries, scientists need to measure the energy spectrum of cosmic rays -- that is, the distribution of particle numbers across different energies.
The research team used observational data collected between 2016 and 2024 by DAMPE, nicknamed Wukong or Monkey King, to precisely measure and map the energy spectra of five types of cosmic-ray particles. They discovered that the quantities of all the different particles exhibited a synchronized sharp decrease upon reaching a specific high-energy threshold.
"It's like cars on a highway. Once their speed reaches a certain limit, the number of vehicles that can continue to accelerate suddenly drops significantly," said Chang Jin, chief scientist of DAMPE and an academician of the Chinese Academy of Sciences (CAS).
Through calculations, the team found that the limit is determined by the particle's charge rather than its mass.
"Simply put, the larger the particle charge, the higher the maximum energy it can be accelerated to," explained Fan Yizhong, a researcher at the Purple Mountain Observatory (PMO) of CAS and deputy chief designer of DAMPE's science application system.
This charge-dependent acceleration model was first proposed by physicists in the 1960s, and more than sixty years later, the DAMPE satellite has provided the first observational evidence for it.
Yuan Qiang, a researcher at PMO and a member of the satellite's science team, said that this study indicates the existence of a natural "super particle accelerator" in the cosmic space relatively close to Earth -- on a scale of about 1,000 light-years.
"Combined with previous studies on the directional distribution of cosmic rays, it can also be determined that this acceleration source is located in a direction far from the core of the Milky Way," Yuan added.
DAMPE, launched into space in late 2015, is China's first astronomical satellite. Its main task is to search for evidence of dark matter through high-precision observation of high-energy cosmic particles, while also studying the origin and propagation of cosmic rays.
The satellite has operated stably in orbit for over 10 years, recording approximately 18.5 billion high-energy particle events. Compared with similar space-based high-energy particle detectors worldwide, DAMPE offers unique advantages, including wide energy coverage, precise energy measurement, and strong particle-identification capability.
"The satellite is still in excellent condition. With further accumulation of data, we look forward to its additional contributions towards ultimately unraveling the mysteries of dark matter and the origin of high-energy cosmic rays," Chang added. ■
