Most theories on particle propagation and acceleration assume that prominent features of cosmic ray spectrum (such as acceleration limits, or changes in the spectral gradient during travel), are sensitive to only a particle’s electrical charge. This could also be explained by the fact that they depend instead on a particle’s mass.
It has always been hard to determine the patterns that nature will follow, mainly because it is difficult to measure the spectrum of individual particles with extremely high energies. The DAMPE, or Dark Matter Particle Explorer (DMPE), was a kind of cosmic telescope that examined the skies to determine if those strange bends and break in the spectra of cosmic rays might be caused by dark matter.
DAMPE’s task is to test whether the known forces are controlling cosmic rays, or if dark matter exerts an unrecognized influence on them.
A new study has published direct measurements of energy spectra from carbon, oxygen and iron cosmic-rays ranging between 20 gigavolts and 100 teravolts. (And up to 60 Teravolts in the case of iron).
The study is based on nine years of observations by the DAMPE satellite telescope.
Measurement of energy spectrum in cosmic-ray nuclei
Researchers observed that particle counts below a certain threshold of energy fell steeply across all nuclei. This acceleration, which is also known as “spectral softerening,” indicates that particle counts are generally declining more quickly. The fall in rigidity around 15 Teravolts has also been larger.
The rigidity of a particle is measured by its resistance to deflection when it encounters magnetic fields. This spectral characteristic, which is independent of the nucleus, appears consistently at the same level of rigidity. Models that concentrate on energy per nucleon, however, are excluded safely with an 99% confidence level.
Andrii Tykhonov is an associate professor at DPNC at the Faculty of Science at UNIGE and the co-author of this study. These particles are also classified according to their energy: low, up to a few billion electron-volts; intermediate, from a few billion to several hundred billion electron-volts; and high, over 1,000 million.
The energy of these particles is also classified: Low, between a few hundred billion and a few thousand billion electron-volts, Intermediate, from several hundred to billions to electron-volts, and High, above 1,000 billion.
Geneva-based team played an important role. Researchers are constantly detecting DAMPE events using these techniques.
They also help obtain important measurements such as proton, helium, and carbon fluxes. They were also at the forefront of developing one of DAMPE’s most crucial instruments, the Silicon-Tungsten Tracker, a sub-detector that is essential to accurately trace particle paths and charges.
There’s something that keeps cosmic rays from reaching the Milky Way galaxy center
The results are a major step forward in understanding the sources of cosmic rays, and processes that control their spread throughout the galaxy. These results provide experimental constraints to refine the models for particle acceleration and propagation in interstellar media. These results together lead to an improved description of the high-energy particles populations within the universe.
Journal Reference
- The DAMPE collaboration. The DAMPE Collaboration. Nature (2026). DOI: 10.1038/s41586-026-10472-0
