<p><span class="math-container">$^{130}$</span>Xe is thought to be produced almost exclusively in stellar interiors by <a href="https://en.wikipedia.org/wiki/S-process" rel="nofollow noreferrer">s-process</a> neutron capture onto pre-existing <a href="https://en.wikipedia.org/wiki/Iron_peak" rel="nofollow noreferrer">iron-peak elements</a> (e.g. <a href="https://iopscience.iop.org/article/10.1086/510881" rel="nofollow noreferrer">Gilmour &amp; Turner 2007</a>).</p>
<p>The s-process reactions are slow (that's what the s stands for); typically it take years to thousands of years between neutron captures onto a particular nucleus and many such neutron captures must take place to build up iron-peak nuclei to <span class="math-container">$^{130}$</span>Xe. i.e. The formation of heavy s-process elements takes thousands of years at least.</p>
<p>A massive primordial star initially contains no elements heavier than He, iron-peak elements are not synthesised in its interior until it reaches the very end stages of its life. This process of making iron-peak elements (known as <a href="https://en.wikipedia.org/wiki/Silicon-burning_process" rel="nofollow noreferrer">silicon burning</a>)  will take hours or days immediately before the core collapses and the star explodes as a supernova.</p>
<p>There is therefore no time to produce <span class="math-container">$^{130}$</span>Xe in the first stars via the s-process and <strong>so <span class="math-container">$^{130}$</span>Xe is a secondary isotope</strong>, which is produced in further generations of stars that form from gas that is already enriched in iron-peak elements.</p>

CC BY-SA 4.0
2023-01-16T00:05:35.493Z
2023-01-16T17:11:20.583Z
2023-01-16T17:11:20.583Z
ProfRob
<p>With the definitions: 'a primary isotope is any isotope which can be synthesised in a star which starts its life containing only hydrogen and helium', and a secondary isotope is any isotope which requires a higher metallicity at the start of the stars life in order to be synthesised.</p>
<p>Is xenon-130 therefore a primary or secondary isotope? Ive read conflicting answers. My reasoning is that to produce xenon-130 you just need a star which can produce iron-56 (therefore just a sufficient mass), and then the s-process, which simply requires an abundance of neutrons, both situations can occur in a first generation star. However many people say that it is secondary.</p>
<p>Can anyone shed any light to clarify?</p>
<p>(im also realising that this may not be the correct forum to ask this question, if not can anyone point me to a relevant place to ask this)</p>

CC BY-SA 4.0
2023-01-15T13:38:55.323Z
Can you add references to what you have read and what people say. Primary s-process in a primordial star would require some way of mixing iron-peak nuclei to regions where there is a supply of free neutrons. Do you have a reference for models where that happens?
ProfRob
<star><stellar-evolution><nucleosynthesis>
In the context of stellar nucleosyntheis, is Xenon-130 a primary or secondary isotope?
ryani42
# In the context of stellar nucleosyntheis, is Xenon-130 a primary or secondary isotope?

(Asked by: username_0 on 2023-01-15)

With the definitions: 'a primary isotope is any isotope which can be synthesised in a star which starts its life containing only hydrogen and helium', and a secondary isotope is any isotope which requires a higher metallicity at the start of the stars life in order to be synthesised.

Is xenon-130 therefore a primary or secondary isotope? Ive read conflicting answers. My reasoning is that to produce xenon-130 you just need a star which can produce iron-56 (therefore just a sufficient mass), and then the s-process, which simply requires an abundance of neutrons, both situations can occur in a first generation star. However many people say that it is secondary.

Can anyone shed any light to clarify?

(im also realising that this may not be the correct forum to ask this question, if not can anyone point me to a relevant place to ask this)

**Tags:** star, stellar-evolution, nucleosynthesis
> **Comments:**
> **username_1**: Can you add references to what you have read and what people say. Primary s-process in a primordial star would require some way of mixing iron-peak nuclei to regions where there is a supply of free neutrons. Do you have a reference for models where that happens?  

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## 1 answers

### Answer by username_1 on 2023-01-16. Score: 3

$^{130}$Xe is thought to be produced almost exclusively in stellar interiors by [s-process](https://en.wikipedia.org/wiki/S-process) neutron capture onto pre-existing [iron-peak elements](https://en.wikipedia.org/wiki/Iron_peak) (e.g. [Gilmour & Turner 2007](https://iopscience.iop.org/article/10.1086/510881)).

The s-process reactions are slow (that's what the s stands for); typically it take years to thousands of years between neutron captures onto a particular nucleus and many such neutron captures must take place to build up iron-peak nuclei to $^{130}$Xe. i.e. The formation of heavy s-process elements takes thousands of years at least.

A massive primordial star initially contains no elements heavier than He, iron-peak elements are not synthesised in its interior until it reaches the very end stages of its life. This process of making iron-peak elements (known as [silicon burning](https://en.wikipedia.org/wiki/Silicon-burning_process)) will take hours or days immediately before the core collapses and the star explodes as a supernova.

There is therefore no time to produce $^{130}$Xe in the first stars via the s-process and **so $^{130}$Xe is a secondary isotope**, which is produced in further generations of stars that form from gas that is already enriched in iron-peak elements.


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