All Questions
Tagged with event-horizon angular-momentum
29 questions
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When two black holes spinning in opposite directions approach one another is the Kerr metric destroyed as two regions of frame-dragged space meet?
The kerr metric describes the frame-dragged space just outside a spinning uncharged black hole. I have read in popular science articles that frame dragging is like a stick spinning in treacle causing ...
user441992
2
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1
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91
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What happens when you shine circularly polarized light at a pole of a rotating black hole?
Circularly polarized light carries spin angular momentum (SpAM 😉), so shining it into a pole of a spinning black hole from a point on the rotation axis of the BH should raise the angular momentum of ...
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4
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Is a black hole spherical?
Black holes are usually created when massive stars use up all their fuel and collapse due to gravitational collapse.
All stars rotate.
However, since angular momentum must be conserved even when they ...
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Exact meaning of the mass $M$ in the Kerr metric event horizon?
Posting this as I have so far not been able to find a straightforward answer to the following question. The formula for the outer event horizon of a kerr black hole is given by the following equation:
...
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Can a Kerr black hole become super-extremal?
Let's assume there is a large Kerr black hole, which is almost
extremal and would become extremal with the addition of a small
amount of mass $M$ with spin $J$ to make the final $J=M$.
What if this ...
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3
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Why does rotation make black holes smaller?
A non-rotating black hole has a Schwarzchild radius of $2GM/c^2$. A rotating black hole of the same mass has a smaller outer horizon radius, down to a limit of $GM/c^2$ at the fastest possible ...
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What is spinning in a spinning black hole? [duplicate]
When a rotating star collapses into a neutron star, the resulting object spins at a huge number of rpm due to its much smaller volume and the conservation of angular momentum. What happens when a ...
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When black holes rotating in opposite directions meet does frame dragging stop where they meet?
Does spacetime stop being dragged when counterclockwise rotation meets clockwise rotation for black holes of equal mass?
user353451
2
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3
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Astrophysical vs. Schwarzschild Black Holes
I have heard the idea that real astronomical black holes cannot be called Schwarzschild BHs, not because of rotation but because Schwarzschild contains no mass and is eternal, due to being a ...
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Does the angular momentum of a Black Hole give insight into a potential solution for the singularity?
Alright so, i want to make one thing clear. I am a bit of a dumbass who watches a lot of PBS Spacetime and read a paper or to on visualising Black Holes. Example image (10k):
I asked a very similar ...
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Could the spin of a Black Hole give us insight into the size of the core? [closed]
As we know the conservation of angular momentum seems to be rather true and applies to black holes as well. We know that they spin and we also know the relationship between angular velocity and radius....
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Rotating black hole
I know that everything that is shaped from gravity force is rotating, and gravity is a central force. but I want to know how can we detect that a black hole has an angular momentum? By which ...
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1
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Speciality of rotating black holes? [closed]
I have read that there are different properties of black hole which are rotating like, they drag the spacetime, with them. Also I read that they have kind of 'ergosphere' along with event horizon. ...
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1
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What is the physical shape of a rapidly spinning singularity?
Let's say I have a star 20x the mass of the sun. At the end of its life, it collapses into a black hole. Now correct me if I am wrong, but as it collapses it rotational speed dramatically increases ...
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What happens if an object spins faster than light? [closed]
Does a star disappears from space time, if it spins faster than light?
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How can black hole rotate? [duplicate]
I was reading about black holes and I've found part saying that black hole is a point and anther saying that black hole can rotate. However the points are dimensionless, so they can't rotate - How can ...
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Can black hole experiences Coriolis effect?
The weather here are thanks to Earth's rotation, so would there be any coriolis effect however tiny occurs when black hole rotates?
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Black hole and the continuum of laws in normal space
I have heard it said that the laws of physics break down inside a black hole. I find it hard to believe that the law of conservation of angular momentum would not operate inside a black hole. Are some ...
4
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1
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What is exactly rotating in a rotating black hole?
I have read this:
https://arxiv.org/abs/gr-qc/9404041
In General Relativity the black hole solutions which have so far been found
form a four parameter family called the generalized Kerr-...
- 29.3k
4
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1
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"Black hole spins at $X$% of the speed of light", what does that mean?
I've seen a few news stories recently (example, example) about some black holes spinning at X% of the speed of light. What does that mean? What exactly is moving at that speed, and with respect to ...
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Rotating Black Holes
All stars rotate. And the more they contract the faster the rotation, so is there such a thing as a non-rotating black hole? And as gravity is less at the equator of a rotating star, assuming that ...
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What does that mean, a black hole "rotates"? [duplicate]
A black hole has:
a mass
electrical charge
angular momentum?
In the inner, there is a singularity, all the mass, collapsed to one point.
The event horizon is surrounding that singularity.
How can a ...
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3
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How can a black hole rotate if time dilation stops time at the event horizon?
How does a black hole rotate if time is dilated to infinity (e.g. stopped) at the event horizon? Note: this is relevant to this question, but different: How can a singularity in a black hole rotate ...
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Why are black holes depicted as disks and not spheres?
Surely light gets 'pulled' in from all directions in 3D space so the event horizon would not be a round disk, but rather a sphere of light - meaning black holes should actually be light holes?
My ...
2
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Does the event horizon of a black hole need to be an oblate sphere?
Suppose two black holes where rotating around each other, perhaps spinning into each other, at a distance such that their event horizons merge into one event horizon. It seems to me that the event ...
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How fast does a black hole spin? [duplicate]
When a star dies it explodes in a supernova. This happens when heavier elements like iron is fused in the core of the star. Then the star collapses under its own gravity. This leaves a black hole ...
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3
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Why does angular momentum shorten the Schwarzschild Radius of a black hole?
Angular momentum causes the event horizon of a black hole to recede. At maximum angular momentum, $J=GM^2/c$, the Schwarzschild radius is half of what it would be if the black hole wasn't spinning.
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How can a singularity in a black hole rotate if it's just a point?
I guess nobody really knows the true nature of black holes, however, based on everything I know about black holes, there is a "singularity" at their center, which has finite mass but is infinitely ...
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How can a black hole have spin?
How is it possible, or even meaningful, to say that a black hole has spin? (Tangentially, if the singularity is assumed to be a point, it must have either zero or infinite angular momentum, in both ...
user40753