Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one step. Numbers come from NASA, LIGO, USGS and LANL; the pictures are not to scale.
Tap the buttons and watch what happens.
Zoom into the gold, then add or remove a proton. What element do you get?
The proton count (Z) fixes the element. Step Z from 76 to 82 with the neutrons fixed at 118 and watch gold become platinum or mercury.
Zoom in. Tap the buttons. Is it still gold?
A sketch, not to scale.
Fuse bigger and bigger atoms. What happens to the energy at iron?
Binding energy per nucleon peaks around iron (and nickel). Fuse up the ladder: every step releases energy until iron, then fusion absorbs it.
Tap Fuse. When does the star get stuck?
Curve values are rounded textbook numbers.
Pick trickle or flood, then fire neutrons at an iron nucleus. Which one reaches gold?
Captures add mass; beta decay turns a neutron into a proton. With a slow trickle an unstable nucleus usually decays before the next capture; a flood lets it swallow dozens first.
A simplified model tuned so a flood of 141 neutrons on iron-56 ends at gold-197.
Watch two neutron stars spiral in, send out ripples, and crash. What comes flying out?
The orbit shrinks as gravitational waves carry energy away, then the merger throws out freshly made heavy elements: a kilonova.
Tap the button. Watch them spin and crash!
Not to scale.
Tap the Earth to drop asteroids. Where does their gold end up?
Core formation took most precious metals out of the mantle; a bombardment after the core formed added more to the outer layers.
Tap the Earth. Where does the gold land?
A sketch: not to scale.
Swirl the pan. Why does the gravel wash out while the gold stays?
Natural gold (density 16–19.3) is about seven times denser than ordinary rock (~2.5), so it sinks while the water carries light gravel over the rim.
Swirl the pan. What stays at the bottom?
Gold is very, very old. The gold in a ring is older than the whole Earth!
Stars are giant hot balls in space. They squeeze tiny bits together to make new stuff. But squeezing only works up to iron. To make gold, nature needs a different trick.
Some stars leave behind a tiny ball that is super heavy, called a neutron star. Long ago, two of them spun around each other and crashed. Boom! A glowing cloud flew out, and it was full of brand new gold.
The gold floated through space in giant clouds of dust. One cloud made our Sun and our Earth. Most of the gold sank deep inside the Earth. Then rocks from space crashed down and brought more gold to the top.
Rain and rivers wear away rocks and wash tiny bits of gold into rivers. Gold is very heavy, so it sinks. People swirl a pan in the river. The sand washes away, and the shiny gold stays!
More space stories: how stars are born and how the Big Bang happened. ← More explainers
Gold is made in space, not on Earth. Its atoms are forged in the most violent events in the universe, mainly when two neutron stars crash into each other. In the crash, atomic nuclei are flooded with neutrons and grow into heavy elements like gold and platinum. This is called the rapid neutron-capture process, or r-process.12
That gold drifted through the galaxy and ended up in the cloud of gas and dust that formed our Solar System about 4.6 billion years ago.9 On Earth, most of it sank into the planet's iron core. The gold we mine was probably brought to the outer layers later by asteroids. Then hot water and rivers gathered it into veins and nuggets.67
Gold is a chemical element: a pure substance made of only one kind of atom. What sets an element apart is the number of protons in the nucleus of each atom. Gold has 79.8 Its nucleus also holds neutrons, which add weight but don't change which element it is. Natural gold has only one stable form, gold-197.163 The common form of gold weighs 197 units, so it has 79 protons plus 118 neutrons.8
So "making gold" really means building nuclei with exactly 79 protons. You can't do that with chemistry. Heating, mixing or melting never changes the number of protons in a nucleus. To make gold you need nuclear reactions, and nature only runs the right ones in extreme places.
After the Big Bang, the universe had only hydrogen, helium and a little lithium.3 Stars make heavier elements by nuclear fusion: they squeeze light nuclei together into heavier ones, and that gives off energy. (Our explainer How are stars formed? shows how that fire starts, and How did the Big Bang happen? covers the first elements.)
Big stars keep going: hydrogen to helium, helium to carbon, then oxygen, neon, silicon, and finally iron (26 protons). There the chain stops. Iron's nucleus is one of the most stable of all (the peak is in the iron–nickel group), so fusing it releases no energy. Making anything heavier than iron by fusion takes in energy instead.45 A star can't power itself that way, so fusion can never climb to gold.
To go beyond iron, nature adds neutrons. A neutron has no electric charge, so it can slip into a nucleus easily. That makes the nucleus heavier, but it's still the same element. If a nucleus picks up too many neutrons it becomes unstable, and a neutron changes into a proton (beta decay). With one more proton, the atom moves one step up the periodic table.3
| Slow process (s-process) | Rapid process (r-process) | |
|---|---|---|
| Where | Inside big, ageing stars | Neutron-star collisions (and possibly rare supernovae and magnetar flares) |
| Neutron supply | A trickle, over thousands of years | A flood, in about a second |
| How it climbs | Slowly: an unstable nucleus usually decays before the next neutron arrives | Dozens of neutrons at once, then many decays |
| Makes | Many elements beyond iron: up to about zirconium in big stars,5 and up to lead in smaller ageing stars, so some gold too16 | The heaviest elements, including gold, platinum and uranium3 |
In the neutron flood of a torn-apart neutron star, "single atoms can rapidly capture so many neutrons that they undergo multiple decays," as NASA puts it. That is how you get far heavier elements.3
A neutron star is the crushed core left over after a massive star explodes as a supernova. It holds more mass than the Sun but is only about 20 kilometres (12 miles) across. A teaspoon of its material would weigh about a billion tons.110
On 17 August 2017, the LIGO detectors in the US and the Virgo detector in Italy picked up gravitational waves, ripples in space-time, from two neutron stars spiralling together. The signal is known as GW170817 and lasted about 100 seconds. About two seconds after the gravitational waves arrived, NASA's Fermi telescope caught a burst of gamma rays from the same event. Some 70 observatories on the ground and in space then studied the event, about 130 million light-years away.111
They found a kilonova: a glowing, expanding cloud of debris heated by newly made radioactive elements. Its light showed signs of freshly made heavy elements, including gold and platinum.112 Caltech astronomers estimated that this one collision was forging "more than 10,000 earth-masses of heavy elements."2 The discovery answered a question astronomers had argued about for decades: where about half of all elements heavier than iron are made.1
Neutron-star crashes aren't the whole story. Some supernovae may make heavy elements too.13 A 2025 study found that giant flares from magnetars (strongly magnetic neutron stars) could make up to 10% of the galaxy's elements heavier than iron, perhaps including the very first gold.3
Gold from many cosmic crashes mixed into the galaxy's clouds of gas and dust. About 4.6 billion years ago, one of those clouds collapsed to form the Sun and planets.9 So the Earth had gold from the very beginning.
But the young Earth was mostly molten. Heavy molten iron sank to the centre to form the core, and it took nearly all the precious metals with it. According to University of Bristol researchers, the core holds enough precious metals to cover the whole surface of the Earth four metres deep.7
Why is there any gold near the surface, then? Precious metals are "tens to thousands of times" more common in the Earth's rocky mantle than you'd expect. Nearly four-billion-year-old rocks from Greenland suggest why: a heavy shower of meteorites, about 20 billion billion tonnes of it, hit the Earth after the core had formed, and its gold stayed in the outer layers.7
Gold is scarce in the Earth, but geology concentrates it. USGS describes two main kinds of deposit:6
That difference in density is the secret of the gold pan. Swirl water and gravel, and the light stones wash over the rim while the heavy gold sinks to the bottom. Rockers and sluice boxes use the same idea.6
Panning is how many prospectors start, but most of the world's gold today comes from hard-rock mining: digging out gold-bearing rock, either from giant stepped open pits or through underground tunnels and shafts. South Africa has the deepest hard-rock gold mine, up to about 3,900 metres down.15
Yes, but only in unbelievably tiny amounts. Nuclear reactions can turn one element into another. At CERN's Large Hadron Collider, near-miss collisions between lead nuclei (82 protons) sometimes knock out three protons and leave gold behind. From 2015 to 2018, the LHC made about 86 billion gold nuclei this way. That is only 29 picograms, trillions of times too little for a piece of jewellery.14 Making gold this way works, but it is hopeless as a gold supply: every gold ring is made of gold forged in space.
In two stages. First, gold atoms are made in space, mainly when two neutron stars collide and a flood of neutrons builds heavy elements (the r-process). Then, on Earth, hot water moving through cracks in rock collects tiny traces of gold and deposits them with quartz as veins. Weathering frees that gold, and rivers concentrate it into placer deposits of flakes and nuggets.
The gold atoms themselves come from space. They were forged in extreme cosmic events, mainly neutron-star collisions (the main confirmed source) and possibly some rare supernovae and magnetar flares, billions of years ago. That gold was mixed into the cloud that formed our Solar System about 4.6 billion years ago. Most of Earth's original gold sank into the iron core; the gold we mine was likely added to the outer layers by asteroid impacts after the core formed.
Rocks and rivers never make gold atoms. In nature, gold atoms are only made in extreme events in space (particle colliders can make a few, see below). What the Earth keeps doing is moving and concentrating the gold it already has: hot fluids still form new gold-bearing veins, and rivers still wash gold out of rocks today.
The Earth never makes gold atoms, it only gathers them. Forming a rich gold deposit takes long geological stretches: hot fluids must circulate through rock, and the rock must wear away, before gold collects in veins or riverbeds.
Yes, but only in unbelievably tiny amounts. Nuclear reactions can knock protons out of heavier atoms. At CERN's Large Hadron Collider, near-miss collisions between lead nuclei made about 86 billion gold nuclei during 2015 to 2018, which weighs just 29 trillionths of a gram and falls apart almost immediately. Mining is far cheaper.
Fusion only releases energy for elements up to iron, which has one of the most stable nuclei (the peak is iron and nickel). Fusing iron or anything heavier takes energy in instead of giving it out, so a star's fusion stops at iron. Heavier elements like gold are made by neutron capture instead.
Partly. The gold was made in space before Earth formed, and plenty of it was in Earth from the start, but most of that sank into the core. Research on four-billion-year-old rocks from Greenland suggests the gold we can reach arrived with a heavy shower of asteroids that hit Earth after the core had formed.