<p>My stellar astrophysics text, Francis LeBlanc's <em>An Introduction to Stellar Astrophysics</em>, gives the following quantities for the stages of burning in a <span class="math-container">$25M_{\odot}$</span> star (citing models by <a href="https://ui.adsabs.harvard.edu/abs/2001AnPh...26e...1A/abstract" rel="noreferrer">Arnould &amp; Samyn 2001</a>). This is somewhat less massive than a typical main sequence O5-type star, and with higher masses come higher core temperatures and shorter evolutionary timescales. Nonetheless, it should give you a reasonable order-of-magnitude idea of how long it takes for these processes to play out in a massive star.</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>Phase</th>
<th>Central temperature (K)</th>
<th>Timescale</th>
</tr>
</thead>
<tbody>
<tr>
<td>Hydrogen</td>
<td><span class="math-container">$6.0\times10^7$</span></td>
<td><span class="math-container">$7\times10^6$</span> years</td>
</tr>
<tr>
<td>Helium</td>
<td><span class="math-container">$2.0\times10^8$</span></td>
<td><span class="math-container">$5\times10^5$</span> years</td>
</tr>
<tr>
<td>Carbon</td>
<td><span class="math-container">$9.0\times10^8$</span></td>
<td><span class="math-container">$600$</span> years</td>
</tr>
<tr>
<td>Neon</td>
<td><span class="math-container">$1.7\times10^9$</span></td>
<td><span class="math-container">$0.5$</span> years</td>
</tr>
<tr>
<td>Oxygen</td>
<td><span class="math-container">$2.4\times10^9$</span></td>
<td>6 days</td>
</tr>
<tr>
<td>Silicon</td>
<td><span class="math-container">$4.0\times10^9$</span></td>
<td>1 days</td>
</tr>
</tbody>
</table>
</div>
<p>(One major caveat is that these models are two decades old, and stellar evolutionary codes are constantly being improved. However, I don't believe that these are old enough to be significantly out-of-date!)</p>

CC BY-SA 4.0
2020-12-16T17:51:10.847Z
2020-12-16T17:51:10.847Z
HDE 226868
<p>In a massive star (i.e. an O5 star), first hydrogen is fused into helium, then helium is fused into carbon. This process continues to neon, oxygen, and finally silicon burning. So I am wondering, how long does it take for each process to commence?</p>

CC BY-SA 4.0
2020-12-16T08:45:03.173Z
Here's a timetable for a 25 $M_\odot$ star. https://en.wikipedia.org/wiki/Type_II_supernova#Formation
PM 2Ring
CC BY-SA 4.0
2020-12-16T14:08:47.460Z
@PM2Ring You can use this in an answer :D
WarpPrime
<star><nucleosynthesis>
What is the length of time for each fusion process in a massive star?
WarpPrime
# What is the length of time for each fusion process in a massive star?

(Asked by: username_0 on 2020-12-15)

In a massive star (i.e. an O5 star), first hydrogen is fused into helium, then helium is fused into carbon. This process continues to neon, oxygen, and finally silicon burning. So I am wondering, how long does it take for each process to commence?

**Tags:** star, nucleosynthesis
> **Comments:**
> **username_1**: Here's a timetable for a 25 $M_\odot$ star. https://en.wikipedia.org/wiki/Type_II_supernova#Formation  
> **username_0**: @PM2Ring You can use this in an answer :D  

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## 1 answers

### Answer by username_2 on 2020-12-16. Score: 7 | Accepted answer

My stellar astrophysics text, Francis LeBlanc's *An Introduction to Stellar Astrophysics*, gives the following quantities for the stages of burning in a $25M\_{\odot}$ star (citing models by [Arnould & Samyn 2001](https://ui.adsabs.harvard.edu/abs/2001AnPh...26e...1A/abstract)). This is somewhat less massive than a typical main sequence O5-type star, and with higher masses come higher core temperatures and shorter evolutionary timescales. Nonetheless, it should give you a reasonable order-of-magnitude idea of how long it takes for these processes to play out in a massive star.

| Phase | Central temperature (K) | Timescale |
| --- | --- | --- |
| Hydrogen | $6.0\times10^7$ | $7\times10^6$ years |
| Helium | $2.0\times10^8$ | $5\times10^5$ years |
| Carbon | $9.0\times10^8$ | $600$ years |
| Neon | $1.7\times10^9$ | $0.5$ years |
| Oxygen | $2.4\times10^9$ | 6 days |
| Silicon | $4.0\times10^9$ | 1 days |

(One major caveat is that these models are two decades old, and stellar evolutionary codes are constantly being improved. However, I don't believe that these are old enough to be significantly out-of-date!)


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