Event horizons of merging black holes with 6 to 1 mass ratio

What people said

Recommends benrg · 2021-04 · Physics Stack Exchange · on “Does a finite mass particle pass a black hole event horizon in a finite time for an outside observer?”

I don't think it matters. The only sense in which test particles take forever to cross the event horizon "from the perspective of" someone outside is that news of the crossing, conveyed by light or any other causal signal, takes an unbounded time to reach them. News of events just before the crossing reaches them quickly, though. If you replace the test particle by a small black hole, you'll still never get news of the merging of the event horizon(s), but news of the shape of spacetime just outside the horizon(s) reaches you quickly. In videos of merging black hole horizons, like this one [this video] , they are showing you slices through the manifold they calculated. There's a large element of a

Recommends safesphere · 2023-01 · Physics Stack Exchange · on “Counterintuitive effect between event horizons of a 'binary black hole system'”

When two black holes approach each other, their horizons extend away from their centers and toward each other. Here is a mathematically correct video showing this effect just before two black holes merge into one: [this video]

Recommends safesphere · 2024-02 · Physics Stack Exchange · on “Black Hole Ripped Apart”

A classical black hole of any type (even a not fully formed astrophysical one) cannot be destroyed or ripped apart by anything known to science for several reasons (I hope you get a good answer). In your scenario, the horizons will extend toward each other and merge thus joining three black holes into one. The video in the answer below is horrible. Here is a good one. It shows how the horizons extend, the same would happen for three horizons: [this video]

Recommends safesphere · 2024-07 · Physics Stack Exchange · on “Can black holes fully merge, according to a distant observer?”

@Michael Here is a mathematically correct video from numerical gravity of two black holes merging in the frame of a remote observer. It is quite evident that the moment the horizons touch, the result already is a single larger horizon of an odd shape that very quickly becomes spherical (strictly speaking, never exactly, but this is exponentially negligible): [this video]

Cites Árpád Szendrei · 2020-04 · Physics Stack Exchange · on “Do merging BHs have two or just one singularity?”

There are a lot of questions about BH mergers on this site, and based on those, there are two main possibilities: 1. Initially, the merged BHs, now a joint single BH, have two singularities, that move towards each other. That is, for a certain amount of time, there exist two different singularities inside a single (joint) EH. And based on the statements, it is now unclear whether a merging BH binary has two or just one singularity inside the joint EH. This is after the EHs have joined, that is, when we have a single EH, that incorporates now both BHs, both previously existed singularities. 2. The other argument is, that the joint EH cannot have two singularities, as the singularity is not a

Cites Árpád Szendrei · 2021-10 · Physics Stack Exchange · on “Can information leak through between merging black holes during the merger?”

There are other questions on this site about black hole mergers and information, but none of them answer my question. What happens to information when black holes merge? [LINK] This does not give a satisfactory answer to my specific question. This means that $dr/dt$ cannot change sign once $r<r_s$ . Thus once moving into a black hole ( $dr <0$ ), then the radial coordinate cannot increase. Why radial coordinate of a particle must decrease continuously once it is inside the Schwarzschild radius? [LINK] Nothing can remain stationary and the decrease in the radial coordinate is as inevitable as the increase of the temporal Can information leak through between merging black holes during the merg

Cites safesphere · 2021-10 · Physics Stack Exchange · on “How can anything ever fall into a black hole as seen from an outside observer?”

@Nathaniel "*we only ever observe approximations to black holes, which may merge to form an approximation of a bigger black hole*" - While this is correct +1, it may sound misleading to some. "Approximation" here applies to what merges (the "almost horizons"), but not to the fact that they merge. Two "almost horizons" do merge into one larger "almost hirizon" in seconds by the clock of a remote observer. Anyone thinking they "almost merge" would be incorrect. They do merge into one without approximation. Here is an animation based on numerical gravity: [this video]

Cites safesphere · 2021-10 · Physics Stack Exchange · on “A small black hole asymptotically approaches a big black hole's event horizon. Will it seem to be frozen there, or will it seem to merge?”

"*If the smaller hole glowed brightly enough to be seen, you would see it pancake on the horizon and redshift to invisibility much like an ordinary object of the same size and temperature.*" - This is incorrect. A small black hole already is infinitely redshifted, so the fact that it approaches a big black hole does not affect the redshift. Furthermore, the small black hole will not be flattened. Numerical gravity shows the opposite - the horizons of both black holes extend and protrude toward each other until they unite like two soap bubbles: [this video]

Cites RC_23 · 2023-04 · Physics Stack Exchange · on “Event Horizon Tunnel”

Regarding the following short animation of a merger between a large and small black hole: [this video] The colored surfaces are meant to be the horizons (points of no return). I'm having a hard time understanding the reason for that tunnel that extends between the two momentarily. [LINK] [LINK] Credits: SXS Collaboration After the tunnel forms (2nd image) consider a ray of light that passes exactly through the midpoint of the tunnel (barycenter of the BH's I assume...?), on a path perpendicular to the tunnel. In the case of two planetary bodies or stars in this configuration, the light would be passing through a kind of "saddle" or Lagrange point of gravitational potential, equally balanced betwe

Cites safesphere · 2023-11 · Physics Stack Exchange · on “Falling to a white hole”

To expand on why the “enveloping horizon” logic is wrong, when an object $m$ (let it be a small black hole for example) approaches a black hole $M$, the spacetime between them is curved stronger. Since the position of the horizon depends on the curvature, the horizon of $M$ expands toward $m$ until it “meets” $m$ at $r=2(M+m)$. No “enveloping horizon” forms outside of $m$. Here is a mathematically correct numerical gravity video: [this video] - Finally, since the external metrics are the same, $M$ can be a white hole with exactly the same result.