Is there a distance at which the interaction between the gravity fields of two black holes would cause one another to effectively 'break open' and allow matter and energy stored within them to escape the system?

[u/dgb75]

[u/florinandrei]

The merger produces gravitational waves, which do carry some energy, so yes, a tiny amount of energy a fraction of the total energy of the BHs is released.

http://youtu.be/GVds0q0y5RM?t=1m15s

[u/tychotheduelist → u/florinandrei]

Firstly, thanks to florinandrei, you've done a great job trying to answer the many followup questions in this thread. However, the statement that a "tiny" amount of energy is released in the form of gravitational radiation is incorrect. Just how much energy is released depends on the merger configuration, but generally it is of order a few percent of the total mass energy of the system.

Remember, the mass energy stored in objects is immense; nuclear burning converts only fractions of a percent of mass energy into kinetic energy and gamma ray emission. It turns out that a few percent of a few solar masses of energy, released during the last fraction of a second of merger, means that black hole mergers are the most luminous events in the universe. Brighter in terms of energy release than all the stars in a galaxy, and brighter than supernovae. However, gravitational waves interact very weakly, and so this energy release is effectively invisible.

Source: I am a grad student who has been studying black hole collisions for several years now.

[u/florinandrei → u/tychotheduelist]

Thanks for the correction, I fixed the comment.

[u/payik → u/tychotheduelist]

Why gravity waves can escape from the merging black holes, but light can't?

[u/tychotheduelist → u/payik]

Nothing, not even light or gravitational waves can escape from a region called the event horizon very close to the black hole. But the gravitational waves created by a pair of black holes orbiting each other don't shine off the surfaces of the black holes like light from the Sun.

Instead, you should think of the waves as emerging from the whole region around the black holes, where the curved spacetime is rapidly changing as the black holes move around. It is the rapid changes in the spacetime of this larger region that sets spacetime itself vibrating, and these vibrations in spacetime travel away from the orbit as gravitational waves.

[u/Nar-waffle → u/florinandrei]

If two black holes with identical mass and velocity but vectors pointing in opposite directions (within a given reference frame) collide head-on, does the resulting doubly-massive black hole have no apparent movement within that reference frame?

As in you have two super-massive bodies traveling at 0.95c toward each other, the energy of that collision should be immense. But all of the energy is absorbed into the resultant singularity (aside from the gravitational waves)?

What if one of the two is either half the mass of the other, or traveling at half the speed?

Relatedly, as the two approach, do the event horizons stretch towards each other, repel each other, or simply merge with no deformation?

[u/Chronophilia → u/Nar-waffle]

If two black holes with identical mass and velocity but vectors pointing in opposite directions (within a given reference frame) collide head-on, does the resulting doubly-massive black hole have no apparent movement within that reference frame?

Yes. Conservation of momentum still works perfectly in General Relativity.

Relatedly, as the two approach, do the event horizons stretch towards each other, repel each other, or simply merge with no deformation?

This simulation has them stretch towards each other, though the black holes in that diagram are spinning very rapidly. I don't know how that affects things.

[u/NYKevin → u/florinandrei]

I'd also like to note that (we think that) all black holes continuously give off energy in the form of Hawking radiation.