Coalescing Supermassive Black Holes

Main Question or Discussion Point

Hello all,

I'm currently doing a research paper on the coalescence of two Supermassive black holes (Sagittarius A and the Supermassive black hole at the center of the Andromeda galaxy) and have come across some difficult quandaries.

First since (to an outside observer) nothing ever comes in contact with a Supermassive black hole's Schwarzschild radius, or any black hole's Schwarzschild radius for that matter, how can two black holes coalesce?

Second, if they can coalesce then is it possible to calculate the minimum mass required for an object falling into a black hole to pass the Schwarzschild radius (to an outside observer).

Third, do gravitational waves have interference patterns?

Finally I've heard that gravity is created by matter in motion is this true?
 

Answers and Replies

mathman
Science Advisor
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398
First since (to an outside observer) nothing ever comes in contact with a Supermassive black hole's Schwarzschild radius, or any black hole's Schwarzschild radius for that matter, how can two black holes coalesce?
They will in their own frame.

Finally I've heard that gravity is created by matter in motion is this true?
Gravity waves would be created.
 
182
0
Hello all,
First since (to an outside observer) nothing ever comes in contact with a Supermassive black hole's Schwarzschild radius, or any black hole's Schwarzschild radius for that matter, how can two black holes coalesce?
The Schwarzschild radius is not a constant. It can increase.
 
Chronos
Science Advisor
Gold Member
11,398
738
It may be true it takes forever for the singularities to merge. It is does not take as long for event horizons to merge.
 

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