<p>Stars above about 2.3 M<span class="math-container">$_\odot$</span> smoothly ignite helium in their core before reaching the tip of the red-giant branch and become hotter while they burn helium in their cores, thus entering the blue loop.</p>
<p>However, there are also other stars that may experience blue loops, some of them more than once, see <a href="https://en.wikipedia.org/wiki/Blue_loop" rel="nofollow noreferrer">Wikipedia</a> for a decent explanation.</p>

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2024-07-15T08:29:53.533Z
2024-07-23T22:06:09.940Z
2024-07-23T22:06:09.940Z
Walter
<p>I understand that the blue loop is a loop in the HR diagram performed by stars from 2-8 solar masses. I was curious as to why they occur, but when I researched all I got is that it is when the star begins to fuse helium. However, these stars do not undergo a helium flash as their cores are not degenerate.</p>

<stellar-evolution><red-giant>
Why does the blue loop occur?
Astrovis
# Why does the blue loop occur?

(Asked by: username_0 on 2024-07-15)

I understand that the blue loop is a loop in the HR diagram performed by stars from 2-8 solar masses. I was curious as to why they occur, but when I researched all I got is that it is when the star begins to fuse helium. However, these stars do not undergo a helium flash as their cores are not degenerate.

**Tags:** stellar-evolution, red-giant

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## 1 answers

### Answer by username_1 on 2024-07-15. Score: 2 | Accepted answer

Stars above about 2.3 M$\_\odot$ smoothly ignite helium in their core before reaching the tip of the red-giant branch and become hotter while they burn helium in their cores, thus entering the blue loop.

However, there are also other stars that may experience blue loops, some of them more than once, see [Wikipedia](https://en.wikipedia.org/wiki/Blue_loop) for a decent explanation.


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