<p>It is impossible. After the star is &quot;born&quot;, it will be rotating because of angular momentum from the place it was formed (most likely a nebula, which is the aftermath of a supernova). Even if there are extremely large amounts of magnetic, tidal, etc. forms of weakening the star's rotation, they will weaken as the star's rotation weakens. The stars rotation could become painfully slow (possibly the slowest speed allowed by the universe), but it is still rotating, just extremely slow.</p>

CC BY-SA 4.0
2021-06-30T14:56:42.723Z
Hi Linus, welcome to StackExchange. While your answer may be correct, it doesn't really say anything the accepted answer doesn't. However, if you could back up your claim with references and/or some math/physics, it would actually be an improvement over the accepted.
pela
CC BY-SA 4.0
2021-06-30T13:50:00.437Z
2021-06-30T13:50:00.437Z
Linus Kerman
<p>This is very well possible. If another star passes the two can exchange angular momentum when they meet tangentially. They can even both come out from this encounter with zero rotatiòn. The chances are small but it is possìble.</p>

CC BY-SA 4.0
2021-06-30T09:31:20.040Z
The first and last sentences seem to contradict, in spirit if not in fact.
RonJohn
CC BY-SA 4.0
2021-06-30T09:36:51.187Z
@RonJohn I  see what you mean! Very well possible seems contrary to a very small chance. Maybe I should have written that it is (very well) possible, but... It *is* very well possible though (in fact).
Deschele Schilder
CC BY-SA 4.0
2021-07-01T13:36:55.247Z
The probability is small, but non-zero?
Ng Ph
CC BY-SA 4.0
2021-06-29T19:22:46.037Z
2021-06-29T19:22:46.037Z
Deschele Schilder
<p>It's not physically impossible, but it's so improbable that it may as well be so. You would need every tumbling dust grain and swirl of gas to exactly cancel out the rotation of all the other bits of matter that came together to form the star. If that did happen, the most minuscule disturbance would turn it from a non-rotating star into a slowly-rotating star. It's a reasonable assumption that there are no non-rotating stars within the observable universe.</p>

CC BY-SA 4.0
2021-06-30T14:43:21.227Z
2021-06-30T14:43:21.227Z
Christopher James Huff
<p>No, this is not possible.</p>

<p>During the stellar formation, some angular momentum will always be present. And any "braking" effects (magnetic, relativistic, tidal etc.) will become weaker as the rotation slows down. So the rotation will never completely stop, because any forces slowing down the rotation will weaken as well.</p>

CC BY-SA 4.0
2019-01-30T07:36:56.007Z
well not exactly true, but pretty much true ;-) There could be braking due to tidal effects (or infall) from an object in orbit in the other direction. In that case net angular momentum could change sign, and therefore pass through zero at some instant in time. Then again what does or does not count as "braking".
uhoh
CC BY-SA 4.0
2019-01-30T02:51:10.870Z
2019-01-30T02:51:10.870Z
cuckoo
<p>I'm just curious about that the existence of non-rotating stars. Is it physically possible for a star not to rotate at all? Does magnetic braking eventually stop the stellar rotation?</p>

CC BY-SA 4.0
2019-01-28T03:46:05.860Z
"Is it possible for stars not to rotate?" is a really interesting question! Lack of net rotation during the formation process would have a big impact, I'm looking forward to finding out how. However the question on magnetic braking suggests there are possibly two questions here, 1) can stars form with little or no rotation, and 2) are there any mechanisms by which a rotating star can slow itself down over time.
uhoh
CC BY-SA 4.0
2019-01-28T19:04:04.887Z
How could magnetic braking have an effect? To stop rotation, you need to generate a counter-rotating force, and for a standalone object (the star) this implies that the initial net angular momentum was zero.
Carl Witthoft
CC BY-SA 4.0
2019-01-28T22:47:35.237Z
Magnetic braking occurs through the application of torques to the star either through connection of the magnetic field to the protostellar disc (early in life) or through angular momentum loss through the stellar wind (later stellar life stages). Note that the initial protostellar cloud will have a small amount of rotation from the galactic rotation at a minimum and this would be increased as the protostar contracts. Also proving non-rotation observationally is basically impossible
astrosnapper
CC BY-SA 4.0
2019-01-30T03:05:03.290Z
Rotate relative to what? Relative to an observer on Earth, an orbiting satellite, or something else? IF you mean relative to some static background then yes it is possible, but not very plausible.
Daddy Kropotkin
<star><rotation><stellar-astrophysics><stellar-dynamics>
Is it possible for stars not to rotate?
Study Astrophysics
# Is it possible for stars not to rotate?

(Asked by: username_0 on 2019-01-28)

I'm just curious about that the existence of non-rotating stars. Is it physically possible for a star not to rotate at all? Does magnetic braking eventually stop the stellar rotation?

**Tags:** star, rotation, stellar-astrophysics, stellar-dynamics

> **Comments:**
> **username_1**: "Is it possible for stars not to rotate?" is a really interesting question! Lack of net rotation during the formation process would have a big impact, I'm looking forward to finding out how. However the question on magnetic braking suggests there are possibly two questions here, 1) can stars form with little or no rotation, and 2) are there any mechanisms by which a rotating star can slow itself down over time.  
> **username_2**: How could magnetic braking have an effect? To stop rotation, you need to generate a counter-rotating force, and for a standalone object (the star) this implies that the initial net angular momentum was zero.  
> **username_3**: Magnetic braking occurs through the application of torques to the star either through connection of the magnetic field to the protostellar disc (early in life) or through angular momentum loss through the stellar wind (later stellar life stages). Note that the initial protostellar cloud will have a small amount of rotation from the galactic rotation at a minimum and this would be increased as the protostar contracts. Also proving non-rotation observationally is basically impossible  
> **username_4**: Rotate relative to what? Relative to an observer on Earth, an orbiting satellite, or something else? IF you mean relative to some static background then yes it is possible, but not very plausible.  

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## 4 answers

### Answer by username_11 on 2019-01-30. Score: 4 | Accepted answer

No, this is not possible.

During the stellar formation, some angular momentum will always be present. And any "braking" effects (magnetic, relativistic, tidal etc.) will become weaker as the rotation slows down. So the rotation will never completely stop, because any forces slowing down the rotation will weaken as well.

> **Comments:**
> **username_1**: well not exactly true, but pretty much true ;-) There could be braking due to tidal effects (or infall) from an object in orbit in the other direction. In that case net angular momentum could change sign, and therefore pass through zero at some instant in time. Then again what does or does not count as "braking".  

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### Answer by username_5 on 2021-06-30. Score: 1

It is impossible. After the star is "born", it will be rotating because of angular momentum from the place it was formed (most likely a nebula, which is the aftermath of a supernova). Even if there are extremely large amounts of magnetic, tidal, etc. forms of weakening the star's rotation, they will weaken as the star's rotation weakens. The stars rotation could become painfully slow (possibly the slowest speed allowed by the universe), but it is still rotating, just extremely slow.

> **Comments:**
> **username_6**: Hi username_5, welcome to StackExchange. While your answer may be correct, it doesn't really say anything the accepted answer doesn't. However, if you could back up your claim with references and/or some math/physics, it would actually be an improvement over the accepted.  

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### Answer by username_7 on 2021-06-29. Score: 0

This is very well possible. If another star passes the two can exchange angular momentum when they meet tangentially. They can even both come out from this encounter with zero rotatiòn. The chances are small but it is possìble.

> **Comments:**
> **username_8**: The first and last sentences seem to contradict, in spirit if not in fact.  
> **username_7**: @username_8 I  see what you mean! Very well possible seems contrary to a very small chance. Maybe I should have written that it is (very well) possible, but... It *is* very well possible though (in fact).  
> **username_9**: The probability is small, but non-zero?  

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### Answer by username_10 on 2021-06-30. Score: 0

It's not physically impossible, but it's so improbable that it may as well be so. You would need every tumbling dust grain and swirl of gas to exactly cancel out the rotation of all the other bits of matter that came together to form the star. If that did happen, the most minuscule disturbance would turn it from a non-rotating star into a slowly-rotating star. It's a reasonable assumption that there are no non-rotating stars within the observable universe.


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