Gold is a very valuable material, which is used in a great variety of industries. On Earth, this material is extracted from mines, and can also be found (in small quantities) in some rivers. However, gold didn’t appear from anywhere on the Earth. So, what is the origin of the gold that exists on Earth?
Stars get their energy by fusing elements that are found inside them, and in this process, they form more heavy ones. For example, stars start by fusing hydrogen, and they convert it into helium (which is then once again fused). However, when arriving at iron, this process doesn’t generate energy, but it consumes it. It is at this moment that the star collapses under its own weight, and it explodes in the form of a supernova (which can shine more than a whole galaxy).
Many texts claim that it is in these explosions that the heaviest elements, such as gold or uranium, are formed. However, the simulations of supernovae don’t show these materials to be produced. This represented a problem, as supernovae were the only phenomenon we could think of as the origin of these elements, such as gold.
Neutron stars collisions
Thanks to the proposed difficulties, a new idea arose on how could gold (and other more heavy elements) be formed in the universe.
Neutron stars are the stellar remainders of massive stars, they are mainly formed out of neutrons, and they have an enormous density (a coffee tablespoon of the material of these bodies could weigh as much as Mount Everest). These stellar remainders can be found in pairs, orbiting around a common centre. In these cases, and after billions of years, the two neutron stars can brutally collide.
As the simulations of these systems show, in the instants of the collision (and by a process through which, by bombarding an element with neutrons, the latter can end by converting itself in a much heavier element) is where gold, uranium, and many other elements that we see in the universe are created.
So, the gold, platinum and many other materials that nowadays are extracted from mines on the Earth were formed, billions of years ago, in neutron star collisions.