This plot shows the fitted fraction of protons, helium nuclei, nitrogen nuclei and iron nuclei found in cosmic rays by the Auger experiment. The Auger collaboration has recently released its latest result on the composition of ultra-high-energy cosmic rays (UHECRs) — particles that reach us from beyond our solar system — for energies above 7×1018 eV. Similar to the way particle beams generated by accelerators strike and interact with material in a stationary target, UHECRs interact with nuclei in the…