China's dark matter detection satellite reveals key mechanism behind cosmic ray acceleration

China's Dark Matter Particle Explorer (DAMPE) satellite, also nicknamed "Wukong" (Monkey King), has achieved a major breakthrough in cosmic ray research, 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 Earth.

The study, published in the academic journal Nature on Wednesday, sheds light on the long-standing mystery of cosmic ray origins.

Cosmic rays are streams of high-energy particles, including atomic nuclei, electrons, and positrons, that travel near the speed of light. They originate from extreme cosmic phenomena such as supernova remnants, neutron stars, and black holes, acting as "messengers" that carry critical information about the universe's most violent environments. Despite long time of study, humanity had not found definitive answers to questions such as the origin of cosmic rays.

Using observational data collected by DAMPE between 2016 and 2024, the research team, led by the Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences (CAS), precisely measure and map the energy spectra of five types of cosmic-ray particles: protons, helium, carbon, oxygen, and iron. 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 a CAS member.

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 PMO and deputy chief designer of DAMPE's science application system.

This charge-dependent acceleration model was first proposed by Danish physicists in 1961, but limitations in observational technology prevented its verification for over six decades. DAMPE's unprecedented detection capabilities have provided the first direct observational evidence for the theory.

The findings indicate the existence of a natural "super particle accelerator" 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," said Yuan Qiang, a researcher at PMO and a member of the satellite's science team.

Since its launch in 2015, DAMPE has recorded about 18.5 billion high-energy particle events. Its wide energy coverage, precise energy measurements, and strong particle-identification capabilities make it unique among space-based cosmic ray detectors worldwide.

"The satellite is still in excellent condition," said Chang. "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."

(With input from Xinhua)