<p>The Big Bang theory predicts that (depending what assumptions you choose) the <a href="http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis" rel="nofollow">initial elements</a> were formed from 10 seconds to 20 minutes after the Big Bang.</p>

<p>The initial elements were </p>

<ul>
<li><p>mostly hydrogen</p></li>
<li><p>some deuterium </p></li>
<li><p>some helium-3 and helium-4</p></li>
<li><p>a little lithium-7</p></li>
<li><p>a couple of unstable isotopes that decayed to lithium-7 or helium-3.</p></li>
</ul>

<p>As the linked Wikipedia article says</p>

<blockquote>
  <p>Essentially all of the elements that are heavier than lithium and beryllium were created much later, by <a href="http://en.wikipedia.org/wiki/Stellar_nucleosynthesis" rel="nofollow">stellar nucleosynthesis</a> in evolving and exploding stars.</p>
</blockquote>

<p>So the answer to your question is: the Helium came first.</p>

CC BY-SA 3.0
2015-03-18T18:01:14.513Z
Correction: most helium came first.
Florin Andrei
CC BY-SA 3.0
2015-03-18T21:22:12.260Z
@Florin Not sure what you mean; can you clarify? The answer says the helium came first, before stars. 75% of BBN output was hydrogen by mass.
andy256
CC BY-SA 3.0
2015-03-18T23:11:36.253Z
Right. I'm just saying, some of the helium that exists today, a fraction of it, was made by stars, much later after the Big Bang.
Florin Andrei
CC BY-SA 3.0
2015-03-18T23:51:35.477Z
@Florin Ok. Interestingly, most of the helium on Earth comes from radioactive decay of heavy elements.
andy256
CC BY-SA 3.0
2015-03-18T03:41:54.270Z
2015-03-18T03:41:54.270Z
andy256
<p>This seems to be a chicken and egg problem, the sun begins shining due to hydrogen becoming helium, but it's odd that there was no helium initially without the stars.</p>

<p>Is my logic flawed?</p>

<p>(Note: First year astronomy student)</p>

CC BY-SA 3.0
2015-03-18T10:40:11.217Z
The helium abundance in the universe has hardly changed since after nucleosynthesis in the big bang which created about 23% He by mass. The figure *now* in the interstellar medium of our Galaxy is estimated to be   around 25%.
ProfRob
CC BY-SA 4.0
2019-08-01T13:20:15.117Z
This may not be what you intended by this question, but the object that would become the sun was 'shining' before the p-p chain was able to activate in the core, due to gravitational contraction. This proto-sun of course developed from a cloud with ~24% He, so He existed before the sun on all accounts.
ShroomZed
<star><the-sun><helium>
What came first: the Sun shining or the existence of helium?
Tangent
# What came first: the Sun shining or the existence of helium?

(Asked by: username_0 on 2015-03-18)

This seems to be a chicken and egg problem, the sun begins shining due to hydrogen becoming helium, but it's odd that there was no helium initially without the stars.

Is my logic flawed?

(Note: First year astronomy student)

**Tags:** star, the-sun, helium

> **Comments:**
> **username_1**: The helium abundance in the universe has hardly changed since after nucleosynthesis in the big bang which created about 23% He by mass. The figure *now* in the interstellar medium of our Galaxy is estimated to be   around 25%.  
> **username_2**: This may not be what you intended by this question, but the object that would become the sun was 'shining' before the p-p chain was able to activate in the core, due to gravitational contraction. This proto-sun of course developed from a cloud with ~24% He, so He existed before the sun on all accounts.  

---

## 1 answers

### Answer by username_3 on 2015-03-18. Score: 4 | Accepted answer

The Big Bang theory predicts that (depending what assumptions you choose) the [initial elements](http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis) were formed from 10 seconds to 20 minutes after the Big Bang.

The initial elements were

* mostly hydrogen
* some deuterium
* some helium-3 and helium-4
* a little lithium-7
* a couple of unstable isotopes that decayed to lithium-7 or helium-3.

As the linked Wikipedia article says

> Essentially all of the elements that are heavier than lithium and beryllium were created much later, by [stellar nucleosynthesis](http://en.wikipedia.org/wiki/Stellar_nucleosynthesis) in evolving and exploding stars.

So the answer to your question is: the Helium came first.

> **Comments:**
> **username_4**: Correction: most helium came first.  
> **username_3**: @Florin Not sure what you mean; can you clarify? The answer says the helium came first, before stars. 75% of BBN output was hydrogen by mass.  
> **username_4**: Right. I'm just saying, some of the helium that exists today, a fraction of it, was made by stars, much later after the Big Bang.  
> **username_3**: @Florin Ok. Interestingly, most of the helium on Earth comes from radioactive decay of heavy elements.  

---

