All Questions
44
questions
17
votes
1
answer
1k
views
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 ...
- 751
6
votes
2
answers
1k
views
What happens to the ring singularities when two Kerr black holes merge?
Imagine two Kerr black holes with ring singularities oriented in different axes (e.g. one horizontal and the other one vertical). If they merge, what will happen to these singularities? Will they form ...
- 185
0
votes
2
answers
135
views
Does someone falling into a spinning black hole see the end of the universe?
It is well known that if you fall into the Schwarzschild black hole you cannot see the entirety of the outside spacetime since there are photons which cannot catch up with you before you reach the ...
- 572
3
votes
2
answers
109
views
Perimeter of Kerr's event horizon
We can compute the "proper circumference" of the Schwarzschild event horizon integrating its line element along its perimeter at a fixed $t$. This would be the minimum length of a rope that ...
- 33
0
votes
1
answer
120
views
What would Hawking radiation look like from inside the event horizon?
Let’s say you fell into a rotating black hole, the inner horizon of the black hole is an infinite blue shift surface, so you should be able to observe events from the arbitrarily far future before ...
- 2,908
1
vote
1
answer
113
views
How can I make the Kerr black hole surfaces scale well in my diagrams?
I've read that the equatorial radius of the ergosphere of a rotating black hole is the Schwarzschild radius. But in this animation made in natural units by Yukterez it doesn't apply.
I then used ...
3
votes
1
answer
125
views
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 ...
- 31
1
vote
0
answers
88
views
What specifically prevents the geodesics in Kerr BH from continuing beyond the second world line located inside the inner event horizon?
In a Kerr black hole, the inner event horizon is also called the Cauchy horizon. According to the answer to the question linked here, why are inner horizons Cauchy horizons, the Cauchy horizon only ...
5
votes
2
answers
350
views
How do we determine whether a surface is an event horizon? Exactly what to calculate to do this?
Event horizons play an important role in relativistic astrophysics, especially for black holes, but also for other spacetimes. It is fundamental to be able to determine whether a given surface is an ...
3
votes
1
answer
311
views
Are rotating black holes producing a frame dragging effect inside the event horizon?
Are rotating black holes producing a frame dragging effect inside the event horizon? Is that effect moving space inside the event horizon at speeds far greater than the speed of light?
- 2,255
1
vote
1
answer
184
views
Finding event horizon and ergosphere
I am trying to calculate the event horizon and ergosphere of the Kerr metric. However, I could not seem to find a proper derivation or formula to calculate the event horizon and ergosphere. Could ...
user161157
1
vote
0
answers
84
views
Outer horizon in the Kerr metric
I have a question about the horizon of a Kerr black hole. Assuming that the metric has a coordinate singularity for $\Delta=0$, namely when $$r_\pm=GM\pm\sqrt{G^2M^2-a^2}$$
how can the outer horizon ...
- 308
6
votes
1
answer
263
views
What is missing to make this depiction of a Black Hole realistic?
So i am working on a Music video as a FX Artist and part of the job is a Black Hole. Now i am fairly confident that i am just about the only one on the team who cares how accurat the party is. But i ...
- 308
1
vote
2
answers
180
views
Watching Kerr Ring Singularity
Can you see light from ring singularity from inside the Cauchy Horizon? In between 2 horizons space and time coordinate swaps places, so the inside region lies at the future. But after crossing Cauchy ...
- 1,161
2
votes
1
answer
228
views
What happens to the ergospheres of two colliding black holes, right before collision?
Let's assume we have two black holes with equal mass. They move towards each other, each heading towards the center of the other black hole. Both black holes rotate with equal speed. What happens to a ...
- 163