Stars exploding as supernovae are the main sources of heavy chemical elements in the Universe. In particular, radioactive atomic nuclei are synthesized in the hot, innermost regions during the explosion and can thus serve as probes of the unobservable physical processes that initiate the blast. Using elaborate computer simulations, a team of researchers was able to explain the recently measured spatial distributions of radioactive titanium and nickel in Cassiopeia A, a roughly 340 year old gas remnant of a nearby supernova.