How are elements such as gold created and why can’t humans creat
In: Chemistry
To expand on the rest of the elements:
Hydrogen exists without anything else because it’s the simplest, most stable form that you get with the rules of the universe – one proton, one electron probably, and maybe a neutron or two.
During the birth of the universe when everything was super hot and dense, some hydrogen was fused by that heat into helium, and perhaps a very small amount of those two were fused into lithium.
Everything between hydrogen and iron comes from stars fusing elements during their normal lifespan. Fusing heavier elements requires more force and provides less energy, so it requires larger stars with more gravity crushing into the core. Main sequence stars like our Sun only fuse hydrogen into helium, and then as a red giant they will fuse some hydrogen and helium into heavier elements, up to maybe carbon and oxygen. Once it runs out of hydrogen and helium, it’ll shrink down into a white dwarf and then cool to a black dwarf.
Fusing elements into iron or anything heavier doesn’t give any energy back at all. You can get more energy out with fission, instead. Stars with enough mass will keep fusing heavier and heavier elements until they start fusing iron. Once this happens, the star will collapse very quickly. Stars are held up against their own gravity by the energy produced through fusion. When they start fusing iron, it sucks up energy which means there’s nothing holding the star up against itself. The outer layers of the star can reach high fractions of the speed of light before slamming into the super dense core. That energy creates another wave of fusion that creates all the elements heavier than iron. It also creates an explosion – a nova or supernova – which blasts the star apart into a nebula and spreads all those elements out into the universe.
It’s likely that different heavy elements are more common in different kinds of novae. For example, many stars are part of binary or trinary systems with stars close together. The larger of the two stars can siphon material away from its partner, getting larger until it explodes. This “type 1a supernova” might be responsible for more of certain elements, while a type 2 supernova (a large star collapsing on its own) might produce more of other elements. Astrophysicists are still figuring that out. Regardless, heavy elements come from supernovae.
Many elements are abundant because they are the decay products of larger, radioactive elements. So, the supernova creates uranium, and the uranium decays into thorium and radium and so on.
Almost everything except hydrogen and helium are made in stars (and a lot of helium is made in stars too). Everything heavier than iron is made in supernovas, while some lighter elements are made during stars’ ordinary lifetimes.
Hydrogen was made during the hadron epoch: a time that started about a millionth of a second after the Big Bang and ended about a second later. This is the time when the universe was cooling down to the point that quarks were starting to settle into their three-color (and color-anticolor) groupings that we call protons and neutrons: the building blocks of atoms.
Helium (and a small amount of lithium) were made during primordial nucleosynthesis: a time that started about 3 minutes after the Big Bang and lasted about 17 minutes. The newborn universe was still cooling down, but was still hot and dense enough that fusion was happening everywhere, almost as though the whole universe was one gigantic star.
Humans can make gold. We’ve even turned lead into gold, using particle accelerators. But the process of making gold is so incredibly expensie that it doesn’t make economic sense: even if you sold all the gold that you made, you would not get enough money to cover the cost of making it.
Any element higher than iron on the periodic table such as gold is made during Supernova. As for creation, humans can make gold it just doesn’t make sense to when we can dig it up due to the cost that would be required to synthesize it.
Stars.
Stars are so big thay they can press hydrogen atoms together to make helium. If they are still big enough, they can push a hydrogen and helium atom together to make lithium, and so on and so forth.
This fusion reaction sends out a ton of energy, pushing out the outer layers of the star.
This works until you get to iron. Iron takes more energy to fuse together than it outputs, so as soon as a star starts fusing iron, it’s energy output drops dramatically. Since it’s energy output drops, the other layers of the star are no longer being pushed out, so they suddenly collapse and slam into the star’s core. This collapse is what we call a supernova. This slam happens with so much energy that it’s able to make all the elements above iron up to uranium (possibly neptunium and plutonium, but no isotopes that last long enough for us to find them in nature).
After this supernova, all those elements are scattered, and that is what eventually formed the Earth and our solar system.
We can make very small amounts of elements (any element) ourselves by slamming subatomic particles together, this is how we made all the elements up to 118, but we can only make very small amounts of each, and it is incredibly expensive to do so.
The way that stars make elements such as gold is the same way that human make elements in particle accelerators. By smashing smaller atoms together with such immense energy that they fuse together and create atoms of larger elements such as Gold. This happens naturally when stars explode in a supernova at the end of their life.
So that is to say, humans CAN create gold. It’s just that the energy & technology requirements to do it that way is much more expensive than mining gold the old fashioned way, and is essentially not worth the expense if your goal is to just have gold to use as a commodity.
Most heavy metals are created when binary neutron stars merge. Bascially stars smash into each other and the atoms smash into each other and merge. Only a small amount is made from supernovas.
>That entirely changed the picture. The math showed that binary neutron stars were a more efficient way to create heavy elements, compared to supernovae
https://space.mit.edu/neutron-star-collisions-are-a-goldmine-of-heavy-elements-study-finds
Here’s a graphic showing which stellar process creates what element.
Contrary to a lot of comments it’s not all fusion and supernova
https://www.sciencealert.com/images/articles/processed/solar-system-periodic-head_600.jpg
The simple version is that after the big bang there was hydrogen and helium. These slowly swirled through space until sufficient collected in one place, which created microgravity, and attracted more and more getting “heavier” as more matter created more gravity and attracted more hydrogen and helium.
All that hydrogen and helium squished into one place created pressure and heat as things got really crowded, and they rubbed against each other and there was a spark and the first star ignited.
The sun continued to “suck in” more hydrogen and helium, and at the core of the sun nuclear fusion took place where the heat and pressure were greatest. Hydrogen and helium were slowly transformed into heavier elements. In some cases something special had to happen for the heavier elements to form, like when a super big star explodes or two stars join together. There’s a cool table that shows this here:
[https://www.sciencealert.com/images/articles/processed/solar-system-periodic-head_1024.jpg](https://www.sciencealert.com/images/articles/processed/solar-system-periodic-head_1024.jpg)
But the simple version is that the amount of heat and pressure required to start the nuclear fission is something we can’t easily do on earth. We’ve done it on a tiny scale, but the problem is that controlling this sort of reaction is so incredibly dangerous and complicated that it’s not really do-able on earth.
So why can’t we just fire a bunch of garbage into the sun and then wait a bit and harvest gold? Because if you check the table making gold requires either a dying low mass star or two neutron stars merging. That’s not something you want happening in your solar system.
The dream is something called “cold fusion” which would allow this sort of process at room temperature, but so far nobody has managed to prove this is actually possible.
As a parting thought, every element of your body (except for the hydrogen and helium) was at one point part of a star and is hundreds of billions of years old. That’s kindof a cool thought. You are made of stars. You are worthy, you are special, you are a star. Be nice to people, because they’re also stars.
As some of the others have stated, gold comes primarily from the collision of two neutron stars, or from the final stage of a low mass star’s life. In the first case, a neutron star is a remnant of a high mass star that went supernova (exploded) in the past. Neutron stars are so dense they are on the doorstep of being black holes. When two are close to each other, they will orbit very rapidly, spiraling towards each other until they eventually collide. Some of their material (which is almost entirely neutrons) is thrown off into space, and this spray of neutron droplets thrown into space will undergo nuclear decay, becoming heavy elements. The decay of neutron droplets to form heavy elements is a type of [r-process](https://en.wikipedia.org/wiki/R-process).
In the second case, at the end of a low mass star’s life, it may under go a phase known as the asymptotic giant branch (AGB). The star will be a relatively large and bright red giant. The core of the star will be very dense and hot, and neutrons released by the fusion reactions taking place there can combine with pre-existing heavy elements to create still heavier elements in what is known as the [s-process](https://en.wikipedia.org/wiki/S-process). Those newly created heavy elements can then bubble up to the surface and be blown into space by the strong stellar winds of the star.
The deposits we see on earth were created via nuclear fusion combining lighter elements in the cores of dying stars during the end of life inward collapse and then those new heavier elements were spread in the dust clouds after the stars explode and dissipate.
Human have created gold in science conditions but it costs a fortune and produces tiny amounts per day with no predictable improvement to costs or yield so we don’t bother compared to just mining the deposits on earth.
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