Element Creation

All stars fuse hydrogen into helium. Medium stars, like our Sun will eventually fuse helium into carbon and oxygen before eventually turning into white dwarfs. It will take stars many times the mass of our Sun to fuse heavier elements. After exhausting helium they’ll burn carbon to neon in centuries, neon to oxygen in a year, oxygen to silicon in months, and silicon to iron in a day, before imploding. This implosion bounces off the iron core and causes a supernova explosion. Above iron, heavier elements are mainly created in supernovae, where there is lots of energy to spare; however, because these are short-lived and (relatively) rare events, elements above iron are rarer than those below.