Colliding black holes: when will linear acceleration end?

In summary, the conversation centered around the possibility of a distant observer seeing a change in acceleration during a head-on collision of two black holes with dissimilar masses. The question was raised about whether there would still be a perceived acceleration once one black hole disappeared beneath the event horizon of the other. Various theories were discussed, including the possibility of a "wobble" or "ringdown" of the new event horizon. It was mentioned that according to LIGO, the ringdown from the first detected black hole merger lasted less than 0.05 seconds. The conversation ended with a question about how long a ringdown might persist.
  • #1
gneill
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I was musing about black hole mergers and what an observer might see for a particularly simple (i.e. blatantly contrived) scenario.

Suppose that there are two (non rotating, un-charged, bog standard) black holes of dissimilar masses heading for a head-on collision. They will accelerate towards each other. The larger one will accelerate at a lesser rate than the smaller one, but the acceleration of both towards each other can be observed.

As they merge, will a distant observer see a change in the acceleration of the bodies, and when the smaller black hole just disappears beneath the the event horizon of the larger black hole (admittedly creating a much larger event horizon for the combined masses), will there still be a perceived acceleration of the combination for some interval? If so, for how long might this observable acceleration persist?

Just curious.
 
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  • #2
Wouldn't this manifest as a 'wobble' of the new event horizon, or a 'ringdown'?
 
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  • #3
Drakkith said:
Wouldn't this manifest as a 'wobble' of the new event horizon, or a 'ringdown'?
Could be. I admit that I'm not up to scratch on the details of black hole interactions. The question arose from an idle curiosity. I was wondering how long after the BH's encountered each other that the perceived accelerations of their centers of mass could be detected.

I wonder how long would a "ringdown" persist? It's kind of a sneaky way of asking how long it takes for events below the event horizon to sort themselves out if that''s even a reasonable question. Probably not.
 
  • #4
gneill said:
I wonder how long would a "ringdown" persist?

According to LIGO, less than 0.05 seconds passed from peak amplitude until the ringdown was no longer detectable in the first detected black hole merger. Perhaps it lasts a bit longer but just isn't detectable from this distance.

1280px-LIGO_measurement_of_gravitational_waves.svg.png
 

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  • #5
Very interesting. Thanks for that!
 
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Related to Colliding black holes: when will linear acceleration end?

1. What is linear acceleration?

Linear acceleration is the rate of change of an object's velocity in a straight line.

2. How do black holes collide?

Black holes can collide when two massive objects, such as stars, orbit each other and eventually merge, forming a larger black hole.

3. What happens during a black hole collision?

During a black hole collision, the two black holes will merge and release an immense amount of energy in the form of gravitational waves.

4. How long does it take for linear acceleration to end during a black hole collision?

The duration of linear acceleration during a black hole collision depends on the mass and velocity of the black holes, but it typically only lasts for a few milliseconds.

5. Can we observe the end of linear acceleration during a black hole collision?

Yes, we can observe the end of linear acceleration during a black hole collision through the detection of gravitational waves using specialized equipment such as the Laser Interferometer Gravitational-Wave Observatory (LIGO).

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