This might be Valentine’s Day, but some of the trappings of the day sound like they might be more suitable for Halloween. That’s because most of the gold in the universe – along with silver and platinum – may have been forged in collisions between dead stars.

Astronomers watched that process in action in 2017, when two neutron stars rammed together. That triggered a burst of gravitational waves – ripples in spacetime that were “heard” on Earth.

A neutron star is the tiny but ultra-dense corpse of a massive star. When two of them collide, they blast out huge amounts of matter. As the material cools, it builds up heavier elements – including gold.

Some of those elements are radioactive. As they decay, they glow, creating a kilonova – a fireball billions of times brighter than the Sun.

Telescopes saw the 2017 outburst less than two seconds after the gravitational waves arrived – the first time a source of the waves was seen in other forms. A recent study found that material from the blast was racing outward at almost half the speed of light.

Astronomers watched the formation of heavy elements almost minute by minute as the cloud of debris expanded. They couldn’t see the formation of gold itself, but they did see related elements. That allowed them to calculate the amount of gold that was created: enough to make 10 planets as heavy as Earth – perhaps providing the raw materials for future golden trinkets.

Script by Damond Benningfield