After a century of searching, scientists have finally uncovered a hidden rule behind cosmic rays, shedding light on these enigmatic high-energy particles that traverse the cosmos. This groundbreaking discovery, made by researchers using the DAMPE (Dark Matter Particle Explorer) space telescope, reveals a universal pattern in the energy spectra of primary cosmic ray nuclei, from lightweight protons to heavier iron nuclei. The findings, published in Nature, offer a significant step forward in understanding the origins and behavior of these powerful particles.
Cosmic rays, the most energetic particles ever observed in nature, surpass the energy levels of particles generated by Earth's most advanced accelerators. Scientists believe they are born from some of the universe's most violent events, such as supernova explosions, black hole jets, and pulsars. The DAMPE mission, launched in December 2015, aimed to investigate the nature of cosmic rays and explore their potential connection to dark matter.
Andrii Tykhonov, an associate professor at the University of Geneva's Department of Nuclear and Particle Physics, explains, 'Cosmic rays primarily consist of protons, helium, carbon, oxygen, and iron nuclei. These particles are categorized by their energy levels: low, up to a few billion electron-volts; intermediate, from a few billion to several hundred billion electron-volts; and high, from 1,000 billion electron-volts and beyond.'
The study's key discovery was a universal pattern in the energy spectra of primary cosmic ray nuclei. For each type of nucleus, the number of particles drops rapidly after reaching a certain threshold, a phenomenon known as 'spectral softening.' This pattern was observed across various particle types, suggesting that cosmic ray acceleration and movement through space are governed by rigidity, the resistance of a particle's path to bending by magnetic fields.
The findings strongly support theories that cosmic ray acceleration and movement are controlled by rigidity, while ruling out alternative explanations based on energy per nucleon. The researchers' confidence in this conclusion is exceptionally high, at 99.999%. The Geneva-based research team played a pivotal role in this discovery, employing advanced artificial intelligence methods to reconstruct particle events detected by the telescope and contributing to crucial measurements and data analysis.
The team also developed the Silicon-Tungsten Tracker (STK), a key instrument on DAMPE that accurately traces particle paths and determines the electrical charge of incoming cosmic rays. These contributions have significantly advanced our understanding of cosmic ray creation and movement through the galaxy, placing tighter constraints on existing models of particle acceleration in astrophysical sources and enhancing our comprehension of high-energy particle behavior in interstellar space.
