Chemical element nucleosynthesis. Animation of a supernova explosion ejecting the names, symbols and atomic numbers of the elements. The elements appear in the order in which they are found in the periodic table. Heavy elements are produced in small amounts in giant stars during their lives, or in supernovae, the explosive death of a giant star. Stars cannot produce energy from elements heavier than iron atomic number 26, but the iron nuclei that are produced get bombarded with neutrons in giant stars or supernovae, producing all the heavy elements in the universe, apart from those heavy, radioactive elements past plutonium, which are made artificially on Earth.