Nuclear fusion is how heavy elements are formed in stars. First, stars fuse hydrogen atoms into helium. Helium atoms then fuse to create beryllium, and so on, until fusion in the star’s core has created every element up to iron… then in a violent explosion, more than half the elements on the periodic table are born. Intense heat from the explosion catalyzes nuclear reactions that were not possible in the core. Escaping elements are bombarded with neutrons, which split inside the nucleus into protons and electrons, generating new unique elements. Iron turns into gold, gold turns into lead, and so on until uranium, the heaviest naturally star-born element, is forged from the ashes.
We are stardust because our bodies are made up of atoms that come from old stars that exploded long ago.