<p>Here is what I get when I run <a href="http://user.astro.wisc.edu/%7Etownsend/static.php?ref=mesa-web-submit" rel="nofollow noreferrer">MESA-Web</a> for the sun, zooming in on the red giant period (top plot: core temperature, middle: triple alpha luminosity, bottom: surface luminosity).</p>
<p><a href="https://i.sstatic.net/bcgyw.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/bcgyw.png" alt="Simulated red giant stage" /></a></p>
<p>When the process sets in, the core temperature rises (after oscillatory transients) to 110 million K, ramping up to 147 MK near the end.</p>
<p>The maximum temperature is however not always in the core, but sometimes in a shell surrounding it. Plotting it versus the core temperature shows there are periods where the shell reaches 200 million K.</p>
<p><a href="https://i.sstatic.net/0zN8A.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0zN8A.png" alt="Core (blue) and maximal shell (red) temperature" /></a></p>

CC BY-SA 4.0
2022-12-13T12:23:10.033Z
2022-12-13T13:42:09.690Z
2022-12-13T13:42:09.690Z
Anders Sandberg
<p>According to this paper: <a href="https://iopscience.iop.org/article/10.1086/342498/meta" rel="noreferrer">https://iopscience.iop.org/article/10.1086/342498/meta</a></p>
<ul>
<li>The core may not be the hottest point of the star, rather that will be where fusion is happening.</li>
<li>At the moment of Helium flash the core is likely to be at around  <span class="math-container">$7\times10^7$</span>K</li>
<li>Core temperature will rise as per the mecahnism you posit but eventually the temperature rise will allow the core to expand (which presumably acts as a limit to the heating)</li>
</ul>
<p>This paper: <a href="https://iopscience.iop.org/article/10.1086/319496/fulltext/006059.text.html" rel="noreferrer">https://iopscience.iop.org/article/10.1086/319496/fulltext/006059.text.html</a> - cited in the above suggests that temperatures at the bottom of the convection layer (the hottest point) will be of the order of <span class="math-container">$&gt;10^8$</span>K</p>

CC BY-SA 4.0
2022-12-13T10:03:08.657Z
Presumably between the two values given above
adrianmcmenamin
CC BY-SA 4.0
2022-12-11T17:10:59.423Z
2022-12-11T17:10:59.423Z
adrianmcmenamin
<p>After the Sun becomes a red giant, it will heat up its core to 100 million kelvins, which initiates the Triple-Alpha fusion process, which heats up the star's core even further and cause it to undergo a runaway thermal reaction, a helium flash.</p>
<p>However, I have not been able to find the final temperature of the core. Meaning that, although the star's core would heat up to 100 million kelvin, since the electron-degenerate core cannot expand, it just gets more hotter. I remember having read a paper where the Red giant's core would reach 1 billion kelvin, but I can no longer find that. What vague info I have in mind, is that the Red Giant's core would be between 100m-1b kelvins.</p>
<p><strong>What would be the core temperature of the Red Giant Sun, after the Triple Alpha process causes it to heat up?</strong></p>

CC BY-SA 4.0
2022-10-27T08:45:03.763Z
Have you tried to use one of the simple web-interfaces to generate 1-D evolution models? e.g. http://user.astro.wisc.edu/~townsend/static.php?ref=ez-web
AtmosphericPrisonEscape
<the-sun><temperature><red-giant><heat>
How hot would the core of the Red Giant Sun be?
Arcturus
# How hot would the core of the Red Giant Sun be?

(Asked by: username_0 on 2022-10-27)

After the Sun becomes a red giant, it will heat up its core to 100 million kelvins, which initiates the Triple-Alpha fusion process, which heats up the star's core even further and cause it to undergo a runaway thermal reaction, a helium flash.

However, I have not been able to find the final temperature of the core. Meaning that, although the star's core would heat up to 100 million kelvin, since the electron-degenerate core cannot expand, it just gets more hotter. I remember having read a paper where the Red giant's core would reach 1 billion kelvin, but I can no longer find that. What vague info I have in mind, is that the Red Giant's core would be between 100m-1b kelvins.

**What would be the core temperature of the Red Giant Sun, after the Triple Alpha process causes it to heat up?**

**Tags:** the-sun, temperature, red-giant, heat
> **Comments:**
> **username_1**: Have you tried to use one of the simple web-interfaces to generate 1-D evolution models? e.g. http://user.astro.wisc.edu/~townsend/static.php?ref=ez-web  

---

## 2 answers

### Answer by username_2 on 2022-12-13. Score: 2 | Accepted answer

Here is what I get when I run [MESA-Web](http://user.astro.wisc.edu/%7Etownsend/static.php?ref=mesa-web-submit) for the sun, zooming in on the red giant period (top plot: core temperature, middle: triple alpha luminosity, bottom: surface luminosity).

[![Simulated red giant stage](https://i.sstatic.net/bcgyw.png)](https://i.sstatic.net/bcgyw.png)

When the process sets in, the core temperature rises (after oscillatory transients) to 110 million K, ramping up to 147 MK near the end.

The maximum temperature is however not always in the core, but sometimes in a shell surrounding it. Plotting it versus the core temperature shows there are periods where the shell reaches 200 million K.

[![Core (blue) and maximal shell (red) temperature](https://i.sstatic.net/0zN8A.png)](https://i.sstatic.net/0zN8A.png)


---

### Answer by username_3 on 2022-12-11. Score: 4

According to this paper: <https://iopscience.iop.org/article/10.1086/342498/meta>

* The core may not be the hottest point of the star, rather that will be where fusion is happening.
* At the moment of Helium flash the core is likely to be at around $7\times10^7$K
* Core temperature will rise as per the mecahnism you posit but eventually the temperature rise will allow the core to expand (which presumably acts as a limit to the heating)

This paper: <https://iopscience.iop.org/article/10.1086/319496/fulltext/006059.text.html> - cited in the above suggests that temperatures at the bottom of the convection layer (the hottest point) will be of the order of $>10^8$K

> **Comments:**
> **username_3**: Presumably between the two values given above  

---

