<p>In a word, no.</p>
<p>A black hole's border or event horizon is just curved space time where the curvature exceeds an escape velocity of the speed of light.   Because the inner mass is thought to be very uniform, with essentially zero mass concentrations, it should be one of the most spherical objects in the universe, even more than the sun.   A black hole's event horizon's spherical shape has nothing to do with Hawking radiation, which is a quantum effect just outside the event horizon.</p>
<p>That said, a rotating black hole has two distinct event horizons.  The inner one is spherical, the outer one is not and that may be a more accurate picture of black holes, so they may not be as spherical as highly spherical stars depending on which event horizon your taking into account.</p>

CC BY-SA 4.0
2021-05-09T12:30:41.607Z
2021-05-09T12:30:41.607Z
userLTK
<p>Like the radiation the Sun gives out to sustain it's circular shape, will Hawking radiation sustain the black hole's shape?</p>

CC BY-SA 4.0
2021-05-09T07:03:10.303Z
Have you read other answers in the [tag:hawking-radiation]  tag?  particularly https://astronomy.stackexchange.com/questions/31635/how-exactly-does-hawking-radiation-decrease-the-mass-of-black-holes
James K
CC BY-SA 4.0
2021-05-09T08:29:43.697Z
Welcome to astronomy SE. Please also make sure you follow the guidance [ask].
B--rian
CC BY-SA 4.0
2021-05-09T08:52:48.583Z
*"the radiation the sun gives out to sustain it's circular shape"* I'm not quite sure what you mean by that. Gravity pulls the Sun into a ball shape. There's a balance between the inward force due to gravity and the outward force due to heat (hot stuff tries to expand). Additionally, the Sun is *slightly* flattened due to its spin.
PM 2Ring
CC BY-SA 4.0
2021-05-09T12:04:26.290Z
@PM2Ring  I'm not sure if this is what he means, but the Sun is unexpectedly spherical.   (article is a little dated, more recent articles give updated details). https://www.theguardian.com/science/2012/aug/16/sun-perfect-sphere-nature
userLTK
CC BY-SA 4.0
2021-05-09T14:03:01.750Z
@userLTK I don't think that's unexpected, the Sun's rotation is slow, with a period of ~25 days at its equator. The centripetal acceleration at the solar equator is ~0.0018658 m/s². The gravitational acceleration is ~274.35 m/s²,  over 147,040 times greater.
PM 2Ring
CC BY-SA 4.0
2021-05-09T15:51:39.890Z
@PM2Ring The article I posted, and other articles mention that the equatorial bulge is less than expected and the result "surprising".  I could try to exercise my math muscles and check, but my math is a little rusty.   Some people have worked out the math in the Physics site and get higher numbers than expected, but only a little higher.   Maybe the writers of the articles exaggerated the surprise to make the article sound more interesting.   https://physics.stackexchange.com/questions/208344/why-is-the-sun-almost-perfectly-spherical
userLTK
CC BY-SA 4.0
2021-05-09T17:54:54.840Z
@userLTK As Qmechanic says in their answer to the question you linked, "we would like to argue that the 20% difference in eq. (7) is mainly due to the fact that the Sun does not spin as a rigid body"
PM 2Ring
CC BY-SA 4.0
2021-05-10T08:37:17.103Z
@PM2Ring maybe, I read too much into the articles and to little into the math.    Fair enough.
userLTK
<black-hole><supermassive-black-hole><hawking-radiation>
What is Hawking radiation?
yor
# What is Hawking radiation?

(Asked by: username_0 on 2021-05-09)

Like the radiation the Sun gives out to sustain it's circular shape, will Hawking radiation sustain the black hole's shape?

**Tags:** black-hole, supermassive-black-hole, hawking-radiation
> **Comments:**
> **username_1**: Have you read other answers in the [tag:hawking-radiation]  tag?  particularly https://astronomy.stackexchange.com/questions/31635/how-exactly-does-hawking-radiation-decrease-the-mass-of-black-holes  
> **username_2**: Welcome to astronomy SE. Please also make sure you follow the guidance [ask].  
> **username_3**: *"the radiation the sun gives out to sustain it's circular shape"* I'm not quite sure what you mean by that. Gravity pulls the Sun into a ball shape. There's a balance between the inward force due to gravity and the outward force due to heat (hot stuff tries to expand). Additionally, the Sun is *slightly* flattened due to its spin.  
> **username_4**: @PM2Ring  I'm not sure if this is what he means, but the Sun is unexpectedly spherical.   (article is a little dated, more recent articles give updated details). https://www.theguardian.com/science/2012/aug/16/sun-perfect-sphere-nature  
> **username_3**: @userLTK I don't think that's unexpected, the Sun's rotation is slow, with a period of ~25 days at its equator. The centripetal acceleration at the solar equator is ~0.0018658 m/s². The gravitational acceleration is ~274.35 m/s²,  over 147,040 times greater.  
> **username_4**: @PM2Ring The article I posted, and other articles mention that the equatorial bulge is less than expected and the result "surprising".  I could try to exercise my math muscles and check, but my math is a little rusty.   Some people have worked out the math in the Physics site and get higher numbers than expected, but only a little higher.   Maybe the writers of the articles exaggerated the surprise to make the article sound more interesting.   https://physics.stackexchange.com/questions/208344/why-is-the-sun-almost-perfectly-spherical  
> **username_3**: @userLTK As Qmechanic says in their answer to the question you linked, "we would like to argue that the 20% difference in eq. (7) is mainly due to the fact that the Sun does not spin as a rigid body"  
> **username_4**: @PM2Ring maybe, I read too much into the articles and to little into the math.    Fair enough.  

---

## 1 answers

### Answer by username_4 on 2021-05-09. Score: 1 | Accepted answer

In a word, no.

A black hole's border or event horizon is just curved space time where the curvature exceeds an escape velocity of the speed of light. Because the inner mass is thought to be very uniform, with essentially zero mass concentrations, it should be one of the most spherical objects in the universe, even more than the sun. A black hole's event horizon's spherical shape has nothing to do with Hawking radiation, which is a quantum effect just outside the event horizon.

That said, a rotating black hole has two distinct event horizons. The inner one is spherical, the outer one is not and that may be a more accurate picture of black holes, so they may not be as spherical as highly spherical stars depending on which event horizon your taking into account.


---

