Help Need description of formation of heavy elements

[peterw]

Hi,

Hope someone here can help. I'm working on explanatory graphics on how nuclear fusion works, and how the elements are formed. In particular, I need to show how elements heavier than iron are formed. The obvious process is as part of a supernova explosion, but for the life of me I can't find any diagrams showing what exactly happens.

What I think I know so far: once you get to iron or heavier you need to pump energy into the reaction to get results. It seems nuclear fusion is replaced by the R and/or S processes, where the huge amount of neutrons released in a supernova explosion slam into the Fe, building it up to heavier elements. Some of these heavier elements are stable, others aren't and decay to stable elements.

OK that's probably a very simplistic explanation, but this needs to be made as easy to understand as possible for our visitors (astronomy exhibition).

So, two questions:

1. Can someone help describe (or even better point me to a diagram) what happens specifically? Even something as simple as Fe + loadsa neutrons = a heavier element?

2. For my own further interest, is this how it would also work for us down here doing it artificially? Do we slam heavier elements into each other and get something new, or do we copy this R/S process and use neutrons instead? And if we do, could someone give me an example reaction?

Thanks for reading this far, any help much appreciated!

Peter

 

[AndyW]

Dear Peter,

Thank you for reaching out for help on this topic. Nuclear fusion is a complex process and explaining it in simple terms can be a challenge. I will try my best to provide a clear explanation and point you to some helpful diagrams.

To start, nuclear fusion is the process of combining two or more atomic nuclei to form a heavier nucleus. This process releases a tremendous amount of energy, which is what powers the sun and stars. The most common type of nuclear fusion is the combination of hydrogen nuclei to form helium, which is what happens in the core of the sun.

However, as you mentioned, elements heavier than iron are not formed through the usual fusion process. Instead, they are formed through a process called nucleosynthesis, which occurs in supernova explosions. During a supernova, the intense heat and pressure causes the nuclei of iron and other elements to capture neutrons, creating heavier elements.

To better understand this process, it may be helpful to look at a diagram of the r-process (rapid neutron capture) and s-process (slow neutron capture). These are the two main processes responsible for the formation of heavy elements in supernovae. You can find a helpful diagram on the website of the European Space Agency (ESA) at this link: https://sci.esa.int/web/lisa-pathfinder/-/59041-nucleosynthesis-in-supernovae.

In terms of your second question, yes, scientists can also artificially create heavy elements through a process called nuclear transmutation. This involves bombarding a target element with high-energy particles, such as neutrons, to induce nuclear reactions and create new, heavier elements. An example of this is the creation of element 118, oganesson, which was achieved through the bombardment of curium with calcium ions.

I hope this information helps you in creating your explanatory graphics. Best of luck with your exhibition! If you have any further questions, please don't hesitate to reach out.

 

[sir-pinski]

Hi Peter,

The formation of heavy elements can be quite complex, but I'll try to provide a simplified explanation for you. As you mentioned, the process of creating elements heavier than iron usually occurs in supernova explosions. This is because the extreme conditions in a supernova, such as high temperatures and pressures, allow for nuclear fusion reactions to occur.

In the core of a massive star, hydrogen is fused together to form helium, and helium can then fuse to form heavier elements like carbon, oxygen, and eventually iron. However, once iron is reached, fusion reactions can no longer produce energy and actually require energy input. This means that the core of the star cannot support itself and collapses, resulting in a supernova explosion.

During this explosion, the extreme conditions allow for the process of neutron capture to occur. This is where free neutrons are captured by nuclei, creating heavier elements. This is known as the r-process (rapid neutron capture) and it is responsible for creating elements heavier than iron, such as gold, silver, and uranium.

The s-process (slow neutron capture) is another process that can occur in the outer layers of a star, where free neutrons are captured more slowly and produce stable, heavier elements like lead and bismuth.

As for your second question, scientists do indeed use the r-process to create heavy elements artificially. This is done in nuclear reactors, where neutrons are fired at stable nuclei to create heavier elements. For example, uranium-238 can absorb a neutron and become uranium-239, which then decays to plutonium-239, a highly radioactive and unstable element.

I hope this helps to clarify the formation of heavy elements for you. If you have any further questions, please don't hesitate to ask. Good luck with your exhibition!