A first-of-its-kind experiment using a chromium ion beam at CERN's ISOLDE facility is helping scientists understand how cosmic rays change as they travel through space. When stars explode, they fling atomic nuclei across the galaxy at near-light speed. These high-energy particles eventually hit detectors on Earth, but the journey itself alters them—creating uncertainty that has long muddled our view of galactic chemistry.
The research addresses a fundamental gap: scientists know what elements are produced in stellar explosions, but not exactly how those elements fragment or interact with interstellar matter en route to Earth. This transformation process has clouded decades of data from cosmic ray detectors. By creating a controlled chromium beam, the team can now simulate what happens to cosmic ray nuclei during their long voyage.
Chromium was chosen because it sits at a critical point in the periodic table—heavy enough to produce measurable fragments, yet light enough to avoid overwhelming complexity. The experiment measured how often the beam's nuclei break apart or capture particles. Early results show fragmentation rates that differ from some theoretical models, potentially forcing a re-evaluation of how scientists interpret cosmic ray data.
If these findings hold, they could refine models used to trace the origin of cosmic rays back to specific supernovae. It would also sharpen estimates of how much matter travels between stars—key data for understanding how elements like carbon and iron spread through the galaxy. Improved models would benefit both astrophysics and studies of galactic evolution.