<p>HDE226868's answer is perfectly correct. Just to add the following important information though.</p>

<p>The s-process is limited to elements lighter than lead and produces little peaks of abundance at certain elements along the s-process path - eg. Ba, Sr, Eu, Y. These are often called s-process elements. All the elements heavier than lead are produced by explosive r-process nucleosynthesis in supernova explosions, colliding neutron stars etc.</p>

<p>The split between r-process and s-process production of heavier than iron (peak) elements is about 50:50. ie They weren't mainly made in supernovae, which is a frequent, incorrect claim.</p>

<p>An update is also in order regarding the site of the r-process. In the past it has been thought that most of the r-processing occurs in the early stages of a supernova explosion. However, theoretical models have really struggled to get the environment as neutron-rich as required to produce the heavier elements - certainly those up around gold, platinum, osmium etc.</p>

<p>In the last few years it has become more popular to think that merging neutron star are the main site of the r-process. This hypothesis received a boost with the observation of a <a href="https://en.wikipedia.org/wiki/GW170817" rel="nofollow noreferrer">gravitational wave source</a> source that appeared to be that of a merging neutron star system coinciding with a <a href="https://en.wikipedia.org/wiki/Kilonova" rel="nofollow noreferrer">kilonova</a> explosion seen in gamma rays, visible and infrared light. The infrared spectrum of the decaying light from this explosion betrays the presence of "lanthanide" elements that are produced in the r-process.</p>

<p>Note however that the rate and yield of such events is highly uncertain. There is plenty of good work which suggests that rare types of core-collapse supernovae (aka "collapsars") are still in fact the dominant source of r-process elements in the Milky Way (<a href="http://ttps://arxiv.org/abs/1901.09044" rel="nofollow noreferrer">Siegel 2019</a>).</p>

<p>The relative contributions of various sites to the r-process remains an unsettled matter. You could also read my answers on this topic in Physics Stack Exchange.  </p>

<p><a href="https://physics.stackexchange.com/questions/231981/heavy-element-production-from-supernova">https://physics.stackexchange.com/questions/231981/heavy-element-production-from-supernova</a> </p>

<p><a href="https://physics.stackexchange.com/questions/7131/origin-of-elements-heavier-than-iron-fe">https://physics.stackexchange.com/questions/7131/origin-of-elements-heavier-than-iron-fe</a></p>

CC BY-SA 4.0
2015-02-17T08:47:46.353Z
2019-01-29T08:49:51.320Z
2019-01-29T08:49:51.320Z
ProfRob
<p>The processes at work are the <a href="https://en.wikipedia.org/wiki/R-process">r-process</a> and the <a href="https://en.wikipedia.org/wiki/S-process">s-process</a>.</p>

<p>The r-process occurs in supernovae. Under the extreme conditions leading up to it, heavy elements are initially blocked from undergoing beta decay to other elements. If a heavy atom captures a nearby neutron, it can go to a heavier isotope or element. This happens multiple times to an atom, producing heavy elements.</p>

<p><a href="https://upload.wikimedia.org/wikipedia/commons/a/a7/Rapid_neutron_capture.svg"><img src="https://upload.wikimedia.org/wikipedia/commons/a/a7/Rapid_neutron_capture.svg" alt="r-process"></a></p>

<p>The s-process is slower, and occurs under less dramatic conditions in asymptotic giant branch (AGB) stars - a certain type of red giant. It also uses neutron capture and the subsequent decay of that neutron into a proton. Over thousands of years, atoms climb to become heavier elements. The s-process, though, requires that there already be some heavy elements in existence, unlike the r-process.</p>

<p><a href="https://upload.wikimedia.org/wikipedia/commons/4/4e/S-process-elem-Ag-to-Sb.svg"><img src="https://upload.wikimedia.org/wikipedia/commons/4/4e/S-process-elem-Ag-to-Sb.svg" alt="s-process"></a></p>

<p>For more information, <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/nucsyn.html">Hyperphysics</a>, <a href="http://www.mso.anu.edu.au/~akarakas/Kodai_Lecture4.pdf">this</a> lecture and <a href="https://www-alt.gsi.de/forschung/kp/kp2/nuc-astro/HeavyElements_e.html">this</a> German site (in English) are very useful.</p>

CC BY-SA 3.0
2018-03-21T00:21:25.747Z
"The r-process occurs in supernovae". Needs revision.
ProfRob
CC BY-SA 3.0
2018-03-22T00:05:28.283Z
@RobJeffries You're right; the LIGO data makes that bit out of date. I'll revise it when I have the time to do it right.
HDE 226868
CC BY-SA 3.0
2015-02-16T23:38:40.380Z
2015-02-16T23:38:40.380Z
HDE 226868
<p>Partly inspired by <a href="https://astronomy.stackexchange.com/q/7663/1909">this question</a>, the end result of stellar fusion is Iron-56 (eventually, after some decay). Then it explodes. How/where then to the heavier elements come from. The answer <a href="https://astronomy.stackexchange.com/a/1411/1909">here</a> mentioned two colliding stars form gold. What process is taking place to form this gold (and I'd assume the rest of the heavier elements)?</p>

<star><element>
Where do the heavier elements come from?
CDspace
# Where do the heavier elements come from?

(Asked by: username_0 on 2015-02-16)

Partly inspired by [this question](https://astronomy.stackexchange.com/q/7663/1909), the end result of stellar fusion is Iron-56 (eventually, after some decay). Then it explodes. How/where then to the heavier elements come from. The answer [here](https://astronomy.stackexchange.com/a/1411/1909) mentioned two colliding stars form gold. What process is taking place to form this gold (and I'd assume the rest of the heavier elements)?

**Tags:** star, element


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## 2 answers

### Answer by username_2 on 2015-02-16. Score: 15 | Accepted answer

The processes at work are the [r-process](https://en.wikipedia.org/wiki/R-process) and the [s-process](https://en.wikipedia.org/wiki/S-process).

The r-process occurs in supernovae. Under the extreme conditions leading up to it, heavy elements are initially blocked from undergoing beta decay to other elements. If a heavy atom captures a nearby neutron, it can go to a heavier isotope or element. This happens multiple times to an atom, producing heavy elements.

[![r-process](https://upload.wikimedia.org/wikipedia/commons/a/a7/Rapid_neutron_capture.svg)](https://upload.wikimedia.org/wikipedia/commons/a/a7/Rapid_neutron_capture.svg)

The s-process is slower, and occurs under less dramatic conditions in asymptotic giant branch (AGB) stars - a certain type of red giant. It also uses neutron capture and the subsequent decay of that neutron into a proton. Over thousands of years, atoms climb to become heavier elements. The s-process, though, requires that there already be some heavy elements in existence, unlike the r-process.

[![s-process](https://upload.wikimedia.org/wikipedia/commons/4/4e/S-process-elem-Ag-to-Sb.svg)](https://upload.wikimedia.org/wikipedia/commons/4/4e/S-process-elem-Ag-to-Sb.svg)

For more information, [Hyperphysics](http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/nucsyn.html), [this](http://www.mso.anu.edu.au/~akarakas/Kodai_Lecture4.pdf) lecture and [this](https://www-alt.gsi.de/forschung/kp/kp2/nuc-astro/HeavyElements_e.html) German site (in English) are very useful.

> **Comments:**
> **username_1**: "The r-process occurs in supernovae". Needs revision.  
> **username_2**: @RobJeffries You're right; the LIGO data makes that bit out of date. I'll revise it when I have the time to do it right.  

---

### Answer by username_1 on 2015-02-17. Score: 10

username_2's answer is perfectly correct. Just to add the following important information though.

The s-process is limited to elements lighter than lead and produces little peaks of abundance at certain elements along the s-process path - eg. Ba, Sr, Eu, Y. These are often called s-process elements. All the elements heavier than lead are produced by explosive r-process nucleosynthesis in supernova explosions, colliding neutron stars etc.

The split between r-process and s-process production of heavier than iron (peak) elements is about 50:50. ie They weren't mainly made in supernovae, which is a frequent, incorrect claim.

An update is also in order regarding the site of the r-process. In the past it has been thought that most of the r-processing occurs in the early stages of a supernova explosion. However, theoretical models have really struggled to get the environment as neutron-rich as required to produce the heavier elements - certainly those up around gold, platinum, osmium etc.

In the last few years it has become more popular to think that merging neutron star are the main site of the r-process. This hypothesis received a boost with the observation of a [gravitational wave source](https://en.wikipedia.org/wiki/GW170817) source that appeared to be that of a merging neutron star system coinciding with a [kilonova](https://en.wikipedia.org/wiki/Kilonova) explosion seen in gamma rays, visible and infrared light. The infrared spectrum of the decaying light from this explosion betrays the presence of "lanthanide" elements that are produced in the r-process.

Note however that the rate and yield of such events is highly uncertain. There is plenty of good work which suggests that rare types of core-collapse supernovae (aka "collapsars") are still in fact the dominant source of r-process elements in the Milky Way ([Siegel 2019](http://ttps://arxiv.org/abs/1901.09044)).

The relative contributions of various sites to the r-process remains an unsettled matter. You could also read my answers on this topic in Physics Stack Exchange.

<https://physics.stackexchange.com/questions/231981/heavy-element-production-from-supernova>

<https://physics.stackexchange.com/questions/7131/origin-of-elements-heavier-than-iron-fe>


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