When a star dies, it generates an explosion of elemental nuclei and hurls them into space. Those elements, called cosmic rays, travel at nearly the speed of light, and eventually some of them encounter manmade detectors. Recording how many of each of these elements show up helps scientists better understand cosmic processes—but despite incredible research advances over the last century, uncertainty around how these elements transform as they travel across the light-years has left fundamental questions about our galaxy’s composition unanswered.