Where do all elements come from? H and He from the Big Bang (first 20 minutes). C, N, O from stellar nuclear burning (CNO cycle). Elements up to Fe-56 from onion-shell burning in massive stars. Fe-56 has the highest binding energy per nucleon (8.79 MeV) — fusion stops here. Gold, platinum and uranium need neutron capture: s-process (AGB stars) or r-process (neutron star mergers). GW170817 (2017) directly confirmed r-process in a neutron star merger.
🚀 Simulate in the browser