Can Two Black Holes Really Collide, Even If They Were Once Stars?

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Discussion Overview

The discussion revolves around the conditions and mechanisms that could lead to the collision of two black holes, particularly focusing on their origins from supernova events and the dynamics of their paths in space. It touches on theoretical aspects, observational evidence, and the implications of black hole mergers.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that for two black holes to collide, they must originate from stars that went supernova in close proximity, raising questions about the survivability of such stars.
  • Others argue that any two objects in space could alter their paths due to mutual gravity, potentially leading to a collision.
  • A participant notes the uncertainty surrounding the number of black holes in the universe and suggests that the sheer number of stars that have died could imply that black hole mergers have occurred historically.
  • There is a suggestion that the merger of black holes could result in the formation of a larger black hole, although this remains speculative.
  • One participant questions the likelihood of black hole mergers in an expanding universe, suggesting that such events may primarily occur within local groups of galaxies.
  • Another participant mentions the detection capabilities of LIGO, questioning the discrepancy between expected and observed merger rates.
  • A later reply challenges the assumption that a star could not survive a nearby supernova, suggesting that a sufficiently massive star could maintain its integrity.
  • Reference is made to a known merged galaxy, OJ287, which is said to exhibit the behavior of having two massive black holes.
  • There is a question regarding the mass of a specific black hole, raising curiosity about its formation and growth over time.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the conditions necessary for black hole collisions, the implications of an expanding universe, and the observational evidence for such events. The discussion remains unresolved with no consensus reached on these points.

Contextual Notes

Some claims depend on assumptions about stellar evolution and the dynamics of black holes, while others reference observational data that may not align with theoretical expectations. The discussion includes speculative elements regarding the nature of black hole mergers and their historical occurrences.

wolram
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For this to happen there must have been two stars that went super nova in close
proximity, if so i find hard to think that a star would survive a very close companion going nova, so how do the two black holes get close enough to collide?
 
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Any two objects flying around in space could pass near each other and mutual gravity could alter their paths enough for them to collide.
 
mathman said:
Any two objects flying around in space could pass near each other and mutual gravity could alter their paths enough for them to collide.

Thats a lot of could s how many black holes are there floating around.
 
wolram said:
Thats a lot of could s how many black holes are there floating around.

There's quite a few, centers of certain galaxies included.

I'm sure this phenomenon that you talk about originally has happened at some point in the history of our universe, given the sheer number of stars that we know of that have died and black holes that we know of (not to mention the countless ones we don't know of), and my guess on this matter (and it is a guess, since we have no idea what happens to something when it hits the singularity of a black hole) is that the masses of the black holes combine to create a bigger one.
 
We are supposed to be living in an expanding universe so i guess the only chance for black hole merger is within local groups of galaxies, has a merged galaxy been observed that exhibit the behavior of having two massive black holes in it.
 
wolram said:
For this to happen there must have been two stars that went super nova in close
proximity, if so i find hard to think that a star would survive a very close companion going nova, so how do the two black holes get close enough to collide?

Why not? I think another star, especially one that is big enough to make a black hole would have enough mass to hold itself together near a supernova.
 
Oj287

wolram said:
We are supposed to be living in an expanding universe so i guess the only chance for black hole merger is within local groups of galaxies, has a merged galaxy been observed that exhibit the behavior of having two massive black holes in it.

Yes, at least one such is known. It's called OJ287.
There was more info released at the recent AAS meeting.
Here's a BBC link:

http://news.bbc.co.uk/1/hi/sci/tech/7181877.stm

Jim Graber
 
The BH is equal to 18 billion suns? has this BH been stoked since time began?
 

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