This fascinating metal has always influenced the life of human civilizations, symbol of wealth and considered by some ancient peoples as an element with magical and divine properties; its origin goes back a long time, very far, even from the stars!

When the universe originated 13,7 miliardi di anni fa con il Big Bang, gli elementi che lo componevano erano solamente 3: hydrogen, trace helium and lithium.

They are the stars, through various cycles of nuclear fusion that take place within them, to generate heavier elements: from hydrogen to helium, from helium to beryllium and, with a series of increasingly complex interactions that can involve even more atomic species at the same time, very heavy elements are obtained, just like gold.

However, not all stars are able to generate it: just think that a star the size of the Sun, towards the end of its life cycle, it is able to originate at most elements such as carbon, which has atomic number six, that is, its nucleus is made up of six protons and six neutrons. Un risultato modesto se consideriamo che il numero atomico dell’oro è settantanove!

Only stars exceeding the size of 10 solar masses (10M) riescono a raggiungere pressioni e temperature necessarie per formare l’oro. Another possible formation process is the collision of two neutron stars, celestial bodies with very high densities. Durante questo fenomeno viene sprigionata una quantità enorme di energia capace di originare il metallo prezioso.

But then how does it manage to be present on our planet?

The elements that make up the solar system come from the death of older stars.

Regardless of the size, all the stars, reached the end of their life cycle, they increase their diameter, a tal punto da non essere più in grado di trattenere, with their gravity, the outermost layers, which are thus dispersed in space.

In stars larger than 10M a state of imbalance is reached such as to generate a supernova, or a huge explosion capable of wiping out a large part of the mass in interstellar space.

The scattered material from different stars can aggregate into nebulae and, if sufficiently dense, can give rise, over time, to a planetary system, how it happened, for example, to our solar system.

Gold is therefore a rather rare element in the universe, as well as on Earth.

Fortunately, there are geological processes capable of concentrating it in deposits that allow man to extract it.

 

Sources:

https://www.gregschool.org/articles9blog/2017/5/14/genesis-of-the-elements-xz53h

https://www.sciencelearn.org.nz/resources/1727-how-elements-are-formed

Insights:

Video on how nuclear fusion takes place (ITA): https://www.youtube.com/watch?v = yA3qjWcLcjI&t=661s