Where the atoms in your bones were forged
The Big Bang produced hydrogen, helium and a trace of lithium. Everything else on the periodic table — the calcium in your bones, the iron in your blood — was assembled later, inside stars.
Fusion, step by step
A star spends most of its life turning hydrogen into helium. When the hydrogen runs low, the core contracts, heats, and starts fusing helium into carbon. Massive stars keep going: neon, oxygen, silicon, each stage faster than the last.
- hydrogen burning: millions to billions of years
- helium burning: about a million years
- silicon burning: roughly one day
Why iron ends it
Fusing anything up to iron releases energy. Past iron it costs energy. When a massive core becomes iron, the furnace switches off, pressure vanishes, and the star collapses in under a second. What follows is a supernova, and the shock scatters the whole inventory into space.
Every atom heavier than helium in your body was manufactured inside a star that died before the Sun formed.
Gold is harder
Supernovae struggle to explain the heaviest elements. In 2017 the collision of two neutron stars was observed in both gravitational waves and light, and the spectrum showed freshly forged heavy elements — an estimated several Earth-masses of gold and platinum thrown out in one event.
The jewellery is, in a precise sense, debris from a collision between the densest objects in the universe.
Cover image: MSFC — Public domain (NASA) (source).