<p>Stars are often produced in groups, when a large cloud of gas collapses under its own gravity and splits up.  Sometimes stars are born solo, when a small cloud collapses and doesn't split up.  <strong>Neither of these processes have anything to do with dark matter</strong>. It is the gravity of the gas and dust, not dark matter that causes the collapse.</p>
<p>The initial formation of large scale structure was guided by dark matter.  If you change the amount of dark matter and visible matter, you will get a different universe. In some universes, spacetime will collapse before stars can form. But dark matter is not required to achieve sustained nuclear fusion in stars.</p>
<p>So the answer is &quot;None&quot;.  And, indeed, there are <a href="https://www.nature.com/articles/d41586-022-01410-x" rel="nofollow noreferrer">galaxies with stars that have very little dark matter</a> (how they formed is a bit of a conundrum)</p>

CC BY-SA 4.0
2023-06-04T21:18:33.923Z
2023-06-04T21:42:28.340Z
2023-06-04T21:42:28.340Z
James K
<p>The average dark matter density in the Galactic plane (where stars are born) near the Sun is about <span class="math-container">$10^{-21}$</span> kg/m<span class="math-container">$^3$</span> (<a href="https://www.aanda.org/articles/aa/full_html/2010/15/aa14385-10/aa14385-10.html" rel="nofollow noreferrer">Salucci et al. 2010</a>) and should be evenly spread (it doesn't clump on scales smaller than galaxies).</p>
<p>In contrast, the density of normal matter in a star-forming molecular  cloud at the start of its collapse is about 1000 times larger (and gets bigger as the cloud collapses).</p>
<p>Thus dark matter plays no role in star formation at level of a cluster of stars</p>

CC BY-SA 4.0
2023-06-05T16:54:19.550Z
More precisely, the dark matter doesn't form clumps within galaxies (since it was heated by the infall). In the conventional CDM picture, DM should form clumps at scales smaller than galaxies, but only in the extragalactic field (and while those clumps could persist in galaxies, they wouldn't be expected to accrete the gas to form stars).
Sten
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2023-06-05T16:37:48.627Z
2023-06-05T16:37:48.627Z
ProfRob
<p>In large spaces where there is a lot of dark matter, Stars are born in groups and not alone, so what is the minimum amount of dark matter to start controlled nuclear fusion in nature?</p>

CC BY-SA 4.0
2023-06-04T18:51:09.433Z
The downvote suggests to me that you need some more context.  Generally this is because you haven't included the background that you have done.  So, what do you mean by "born in groups and not alone"  Where did you learn this.  And secondly how does that connect to a "minimum amount of dark matter to start nuclear fusion". It seems obvious to me that nuclear fusion could star with no dark matter at all... but it's not obvious to you so you need to explain your question more.
James K
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2023-06-04T21:01:39.370Z
on wikipedia and several article it mentions that the stars are born in groups and not alone, you wanted me to put the link of wikipiedia?

and the dark matter acts a large scale between stars so I wanted to know the minimum amount of this matter that is there when the stars begins to be born
z.10.46
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2023-06-04T21:02:40.467Z
Links to the wikipedia pages please
James K
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2023-06-04T21:05:26.133Z
Ok Here are two links that mention that stars are born in groups:https://www.stelvision.com/astro/les-etoiles-naissance-vie-et-mort/#:~:text=Les%20pouponni%C3%A8res%20d'%C3%A9toiles&text=Elles%20naissent%20en%20groupe%2C%20%C3%A0,ainsi%20des%20%C2%AB%20c%C5%93urs%20protostellaires%20%C2%BB.       https://fr.wikipedia.org/wiki/Naissance_des_%C3%A9toiles
z.10.46
CC BY-SA 4.0
2023-06-04T21:17:25.867Z
*Merci*.  Now, how does that connect to a "minimum amount of dark matter to start nuclear fusion".  Dark matter "acts" on a scale between galaxies. It doesn't have much (or anything) to do with the processes the lead directly to the formation of stars
James K
CC BY-SA 4.0
2023-06-04T21:28:47.597Z
No the dark matter acts between the star, the effect of the dark matter is visible on the scale of two stars, and in the place of the birth of the stars there are more than 10 stars or even more who are born in groups .
z.10.46
CC BY-SA 4.0
2023-06-04T21:29:47.033Z
Perhaps you are confusing "le nuage sombre" in which stars are born, with "matière sombre" or "matière noire"  Your two links don't mention dark matter at all.  So  please say how you know that the effect of the dark matter is visible on the scale of two stars,
James K
CC BY-SA 4.0
2023-06-04T21:31:44.157Z
in fact from the birth of a group of stars the effect of dark matter becomes visible so normally can evulate the amount of this matter and also know the minimum amount needed...
z.10.46
CC BY-SA 4.0
2023-06-04T21:33:06.737Z
No. the effects of dark matter do not become visible fro the birth of a group of stars.  It is rather difficult to determine the distribution of dark matter.  Again please like to the page you have read about this.
James K
CC BY-SA 4.0
2023-06-04T21:35:20.243Z
and where does dark matter come from afterwards?, I think the effect can be seen from the birth of stars...
z.10.46
CC BY-SA 4.0
2023-06-04T21:37:11.000Z
for example, to check the position of dark matter since the birth of a group of stars, is it constant?  If the amount of dark matter is constant then it has been there since the birth of stars and a large impact on controlled fusion
z.10.46
CC BY-SA 4.0
2023-06-04T21:58:45.687Z
I don't understand you. I think I have answered your question below.  Please take a look.
James K
<general-relativity>
What is the minimum amount of dark matter to start controlled nuclear fusion in nature?
z.10.46
# What is the minimum amount of dark matter to start controlled nuclear fusion in nature?

(Asked by: username_0 on 2023-06-04)

In large spaces where there is a lot of dark matter, Stars are born in groups and not alone, so what is the minimum amount of dark matter to start controlled nuclear fusion in nature?

**Tags:** general-relativity
> **Comments:**
> **username_1**: The downvote suggests to me that you need some more context.  Generally this is because you haven't included the background that you have done.  So, what do you mean by "born in groups and not alone"  Where did you learn this.  And secondly how does that connect to a "minimum amount of dark matter to start nuclear fusion". It seems obvious to me that nuclear fusion could star with no dark matter at all... but it's not obvious to you so you need to explain your question more.  
> **username_0**: on wikipedia and several article it mentions that the stars are born in groups and not alone, you wanted me to put the link of wikipiedia?  and the dark matter acts a large scale between stars so I wanted to know the minimum amount of this matter that is there when the stars begins to be born  
> **username_1**: Links to the wikipedia pages please  
> **username_0**: Ok Here are two links that mention that stars are born in groups:https://www.stelvision.com/astro/les-etoiles-naissance-vie-et-mort/#:~:text=Les%20pouponni%C3%A8res%20d'%C3%A9toiles&text=Elles%20naissent%20en%20groupe%2C%20%C3%A0,ainsi%20des%20%C2%AB%20c%C5%93urs%20protostellaires%20%C2%BB.       https://fr.wikipedia.org/wiki/Naissance_des_%C3%A9toiles  
> **username_1**: *Merci*.  Now, how does that connect to a "minimum amount of dark matter to start nuclear fusion".  Dark matter "acts" on a scale between galaxies. It doesn't have much (or anything) to do with the processes the lead directly to the formation of stars  
> **username_0**: No the dark matter acts between the star, the effect of the dark matter is visible on the scale of two stars, and in the place of the birth of the stars there are more than 10 stars or even more who are born in groups .  
> **username_1**: Perhaps you are confusing "le nuage sombre" in which stars are born, with "matière sombre" or "matière noire"  Your two links don't mention dark matter at all.  So  please say how you know that the effect of the dark matter is visible on the scale of two stars,  
> **username_0**: in fact from the birth of a group of stars the effect of dark matter becomes visible so normally can evulate the amount of this matter and also know the minimum amount needed...  
> **username_1**: No. the effects of dark matter do not become visible fro the birth of a group of stars.  It is rather difficult to determine the distribution of dark matter.  Again please like to the page you have read about this.  
> **username_0**: and where does dark matter come from afterwards?, I think the effect can be seen from the birth of stars...  
> **username_0**: for example, to check the position of dark matter since the birth of a group of stars, is it constant?  If the amount of dark matter is constant then it has been there since the birth of stars and a large impact on controlled fusion  
> **username_1**: I don't understand you. I think I have answered your question below.  Please take a look.  

---

## 2 answers

### Answer by username_1 on 2023-06-04. Score: 6

Stars are often produced in groups, when a large cloud of gas collapses under its own gravity and splits up. Sometimes stars are born solo, when a small cloud collapses and doesn't split up. **Neither of these processes have anything to do with dark matter**. It is the gravity of the gas and dust, not dark matter that causes the collapse.

The initial formation of large scale structure was guided by dark matter. If you change the amount of dark matter and visible matter, you will get a different universe. In some universes, spacetime will collapse before stars can form. But dark matter is not required to achieve sustained nuclear fusion in stars.

So the answer is "None". And, indeed, there are [galaxies with stars that have very little dark matter](https://www.nature.com/articles/d41586-022-01410-x) (how they formed is a bit of a conundrum)


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### Answer by username_2 on 2023-06-05. Score: 4

The average dark matter density in the Galactic plane (where stars are born) near the Sun is about $10^{-21}$ kg/m$^3$ ([Salucci et al. 2010](https://www.aanda.org/articles/aa/full_html/2010/15/aa14385-10/aa14385-10.html)) and should be evenly spread (it doesn't clump on scales smaller than galaxies).

In contrast, the density of normal matter in a star-forming molecular cloud at the start of its collapse is about 1000 times larger (and gets bigger as the cloud collapses).

Thus dark matter plays no role in star formation at level of a cluster of stars

> **Comments:**
> **username_3**: More precisely, the dark matter doesn't form clumps within galaxies (since it was heated by the infall). In the conventional CDM picture, DM should form clumps at scales smaller than galaxies, but only in the extragalactic field (and while those clumps could persist in galaxies, they wouldn't be expected to accrete the gas to form stars).  

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