Binary black hole event horizon merger
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers and commenters link it as a concrete picture of how two event horizons actually merge, since the combined horizon is not just two intersecting spheres.
Recommended by 1 people across 1 different months, 2017 to 2023.
What it is
A 10-second numerical-relativity animation from the SXS Collaboration showing the event horizons of two spinning black holes (2:1 mass ratio) merging into one. It comes from a Caltech simulation published in Phys. Rev. D 80, 124010 and was rendered with the SpEC code and ParaView.
What people said
Recommends DilithiumMatrix · 2017-01 · Physics Stack Exchange · on “What is the region of space that exists at the center of mass of merging black holes?”
You have some region of space (lets call it the 'center') that is surrounded by black holes (BH), such that their individual event horizons (as spherical surfaces) completely enclose the center. The 'overall' event horizon (EH) of the spacetime are not just intersecting spheres. A spherical event horizon exists for a spherically symmetric blackhole, but as soon as you place two blackholes together, the event horizon is no longer spherical. That is to say that the geometry gets more complicated. This video (which could be better rendered...) gives a good example [this video] . Event horizons are defined (see, here [LINK] or here [LINK] ) based on causal interaction. Mathematically, when geodesics
Recommends DilithiumMatrix · 2017-01 · Physics Stack Exchange · on “Does large angular momentum cause swirly bridges when two black holes merge?”
Yes, I think you're correct that the connection between the two black holes (BH) should be asymmetric, but how to represent that with a drawing may be bit more complicated (even with a single BH). A photon (for example) that is co-rotating with a spinning BH (also called a 'Kerr BH' [LINK] ) is more able to escape than a photon anti-rotating with the BH. This is because of 'frame-dragging' [LINK] , which adds a directional dependence to the spacetime near the BH. There should be an additional asymmetry induced by the orbital motion of the blackholes (i.e. even if neither of them were spinning) in a very similar way, such that the EH are extended along the arcs of motion. This is a (brief) si
Cites PM 2Ring · 2021-02 · Physics Stack Exchange · on “A black hole has no hair, but can it have cellulite?”
@oliver The merging event horizons become a single sphere fairly quickly, see this brief anim: [this video] from an Ethan Siegel article [LINK] . Bear in mind that an event horizon isn't a physical object, it's a mathematical surface, like Earth's equatorial and orbital planes.
Cites AccidentalTaylorExpansion · 2023-01 · Physics Stack Exchange · on “What appears in the wake of a moving event horizon? For 2 merging black holes for example”
@ProfRob which premise do you mean? The fact that the event horizon is a spinning blob has been provided kindly by anna v or can be seen in this video [this video] . The premise that the past lightcone points towards the black hole is just a hunch and I'm not sure if it is true.
Critical Yukterez · 2023-01 · Physics Stack Exchange · on “What appears in the wake of a moving event horizon? For 2 merging black holes for example”
@TimRias wrote: *"Note that what you are seeing in that video is not the even horizon, but rather the shadow of the black hole"* - that's not true, the description [this video] says it shows the event horizons, by which they mean the surfaces [LINK] outgoing light cone null expansion. That is not a raytracing [LINK] of the shadow, that's a projection to the coordinate grid.