<p>Copper is not thought to be primarily <em>made</em> in a supernova. It is thought to be mainly produced by the <a href="https://en.wikipedia.org/wiki/S-process" rel="nofollow noreferrer">s-process</a> of slow neutron capture onto iron-peak nuclei that already exist inside a star. These reactions are <em>endothermic</em>.</p>

<p>The source of the neutrons is still somewhat debated, it could either be from the decay of $^{13}$C in relatively low-mass asymptotic giant branch stars or is more likely from the decay of $^{22}$Ne in more massive evolved stars (e.g. <a href="http://iopscience.iop.org/article/10.1088/0004-637X/710/2/1557/meta;jsessionid=F521A33E8AC70B164FD9E8D19FDF5ED8.c3" rel="nofollow noreferrer">Pignatari et al. 2010</a>).</p>

<p>Below you can see a typical route for producing copper from $^{56}$Fe. The axes of the plot are neutron number on the x-axis and proton (atomic) number on the y-axis. Three neutron captures are followed by a beta decay, a neutron capture, a beta decay, then 3 more neutron captures followed by another beta decay to form $^{63}$Cu.</p>

<p>The net process is
$$ ^{56}{\rm Fe} + 7n \rightarrow \  ^{63}{\rm Cu} + 3e + 3\bar{\nu}_e$$  </p>

<p>The copper is then <em>distributed</em> into the interstellar medium by a later supernova explosion in the same star.</p>

<p>If there are no "seed" iron-peak nuclei (e.g. in the first/second generation of stars), then copper can be inefficiently produced by explosive <a href="https://en.wikipedia.org/wiki/R-process" rel="nofollow noreferrer">r-process</a> neutron capture during supernovae explosions. However, this would not contribute very much to the copper we see on the Earth.</p>

<p><a href="https://i.sstatic.net/2YjW2.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2YjW2.jpg" alt="s-process network"></a> </p>

CC BY-SA 3.0
2016-04-16T21:12:27.733Z
2016-04-16T21:12:27.733Z
ProfRob
<p>What are the reasonable chain of reactions to form copper (63, 29) from ca(40, 20) during supernova explosion? And how it will happen? I do not understand the theory behind it. I thought that the reaction will end at Iron and now it does not make sense to me. </p>

CC BY-SA 3.0
2016-04-16T20:28:09.377Z
Could you give some context as to why you think there is a direct link between copper and calcium.
ProfRob
<supernova>
How to form Copper from Calcium in a supernova explosion?
Berkley J
# How to form Copper from Calcium in a supernova explosion?

(Asked by: username_0 on 2016-04-16)

What are the reasonable chain of reactions to form copper (63, 29) from ca(40, 20) during supernova explosion? And how it will happen? I do not understand the theory behind it. I thought that the reaction will end at Iron and now it does not make sense to me.

**Tags:** supernova
> **Comments:**
> **username_1**: Could you give some context as to why you think there is a direct link between copper and calcium.  

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## 1 answers

### Answer by username_1 on 2016-04-16. Score: 4

Copper is not thought to be primarily *made* in a supernova. It is thought to be mainly produced by the [s-process](https://en.wikipedia.org/wiki/S-process) of slow neutron capture onto iron-peak nuclei that already exist inside a star. These reactions are *endothermic*.

The source of the neutrons is still somewhat debated, it could either be from the decay of $^{13}$C in relatively low-mass asymptotic giant branch stars or is more likely from the decay of $^{22}$Ne in more massive evolved stars (e.g. [Pignatari et al. 2010](http://iopscience.iop.org/article/10.1088/0004-637X/710/2/1557/meta;jsessionid=F521A33E8AC70B164FD9E8D19FDF5ED8.c3)).

Below you can see a typical route for producing copper from $^{56}$Fe. The axes of the plot are neutron number on the x-axis and proton (atomic) number on the y-axis. Three neutron captures are followed by a beta decay, a neutron capture, a beta decay, then 3 more neutron captures followed by another beta decay to form $^{63}$Cu.

The net process is
$$ ^{56}{\rm Fe} + 7n \rightarrow \ ^{63}{\rm Cu} + 3e + 3\bar{\nu}\_e$$

The copper is then *distributed* into the interstellar medium by a later supernova explosion in the same star.

If there are no "seed" iron-peak nuclei (e.g. in the first/second generation of stars), then copper can be inefficiently produced by explosive [r-process](https://en.wikipedia.org/wiki/R-process) neutron capture during supernovae explosions. However, this would not contribute very much to the copper we see on the Earth.

[![s-process network](https://i.sstatic.net/2YjW2.jpg)](https://i.sstatic.net/2YjW2.jpg)


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