A new study in Nature shows that various cosmic ray nuclei, from protons to iron, undergo spectral softening at the same hardness of about 15 teraelectronvolts.
More than a century after their discovery, cosmic rays are still a mystery to scientists. These highly energetic particles travel throughout the universe from distant, powerful sources. The DAMPE (Dark Matter Particle Explorer) space telescope is working to better understand them, including whether dark matter plays a role in how they form.
This international project has now discovered a new and important clue, when researchers identified a common feature among these particles.
The mystery of cosmic radiation
Cosmic rays are the most energetic particles ever discovered, far exceeding anything produced by man-made accelerators on Earth. Their origin is still uncertain, but scientists suspect they are created in extreme environments such as supernova explosions, jets from black holes, or pulsars.
DAMPE, launched in December 2015, was designed to investigate these questions. By analyzing very precise data, researchers discovered a consistent pattern in the energy distribution of primordial cosmic ray nuclei, from protons to iron.
"Cosmic radiation consists mainly of protons, but also of helium, carbon, oxygen and iron nuclei," explains Andrei Tikhonov, one of the authors of the study. "These particles are also classified according to their energy: low (up to a few billion electron volts), medium (from a few billion electron volts to several hundred billion) and high (from a thousand billion electron volts and above)."
The team found that the number of particles drops off more sharply after a certain energy level. This phenomenon, called "spectral softening," reflects a sharper decrease than the gradual decrease typically seen as energy increases.
Implications for the physics of cosmic rays
This change occurs at a stiffness of about 15 teraelectronvolts. Stiffness describes the degree to which magnetic fields affect the trajectory of a particle.
Finding the same pattern in this rigidity across different types of nuclei supports models in which both the acceleration and motion of cosmic rays depend on rigidity. These data strongly challenge competing ideas that focus on the energy per nucleon (energy divided by the number of nucleons in a particle), at a 99.999% confidence level.
Researchers in Switzerland have developed advanced artificial intelligence methods for reconstructing particle events and contributed to precise measurements of proton and helium fluxes, along with carbon analysis. The team also led the development of a key instrument, the silicon-tungsten tracker, which allows scientists to precisely track particle trajectories and measure their charge.
These findings bring scientists closer to understanding the origin of cosmic rays and how they travel throughout the galaxy. The results push new limits on theories about particle acceleration in extreme astrophysical environments and improve models of how these particles travel in interstellar space.
for the scientific article DOI: 10.1038/s41586-026-10472-0
More of the topic in Hayadan:
One response
"Protons (hydrogen) but also from helium, carbon, oxygen and iron nuclei"
The cornerstones of life!