PDA

View Full Version : What Happens When Supermassive Black Holes Collide?



Fraser
2008-Feb-29, 07:40 PM
As galaxies merge together, you might be wondering what happens with the supermassive black holes that lurk at their centres. Just imagine the forces unleashed as two black holes with hundreds of millions of times the mass of the Sun come together. The answer will surprise you. Fortunately, it's an event that we should be [...]

More... (http://www.universetoday.com/2008/02/29/what-happens-when-supermassive-black-holes-collide/)

GOURDHEAD
2008-Mar-01, 03:39 AM
The article states that there is a recoil that kicks one black hole out of the combined galaxies. Why not both? Does the Lens-Thirring effect have a spring constant characteristic that supports this behavior? Does rotation (spinning) have the same manifestation with respect to a black hole as it does to a star? If the black hole(s) is (are) kicked out, how much of the mass of the galaxy will follow due to gravitational coupling? Is there a prediction of the amplitude or frequency of the gravity waves that may be associated with the event? Is it probable that the combined effects of "spin", mutual gravitational attraction, and the powerful magnetic and electric fields attached to the accretion disks of each could interact to "instantly evaporate" each black hole?

Fadingstar
2008-Mar-02, 10:08 PM
I'd be interested to know how they make simulations when forces are approaching infinity. I wonder if these simulations of BH's are - to speak - underestimated.

tdvance
2008-Mar-03, 06:33 PM
does the force approach infinity when you are outside the event horizon? I think it does when you approach the singularity, but I doubt a simulation need be concerned with that.

Fadingstar
2008-Mar-03, 07:00 PM
does the force approach infinity when you are outside the event horizon? I think it does when you approach the singularity, but I doubt a simulation need be concerned with that.

I'd be inclined to think that it does. When two BH's collide, I can't see them bouncing off their event horizons. I would suspect that the forces involved would draw the singularities together - whether they're kicked apart or merge is another point - but the simulation would have to allow for that.

Noclevername
2008-Mar-03, 07:13 PM
I'd be inclined to think that it does. When two BH's collide, I can't see them bouncing off their event horizons.

That's exactly what the simulation says happens; or rather, they bounce off their spins. Bouncing is just a transfer of energy, and HMBH's at galactic cores must have a lot of energy to tranfer.

Fadingstar
2008-Mar-03, 11:02 PM
That's exactly what the simulation says happens; or rather, they bounce off their spins. Bouncing is just a transfer of energy, and HMBH's at galactic cores must have a lot of energy to tranfer.

But the event horizon is not a solid thing! Even if they are spinning the event horizon is just a point where light cannot escape.

http://www.nasa.gov/vision/universe/starsgalaxies/gwave.html

http://www.usatoday.com/tech/science/space/2007-05-17-merging-black-holes_N.htm

Well, it seems I was wrong about the number crunch involved for a simulation, but I still can't see them bouncing off their event horizons.

Noclevername
2008-Mar-04, 01:03 AM
But the event horizon is not a solid thing! Even if they are spinning the event horizon is just a point where light cannot escape.

http://www.nasa.gov/vision/universe/starsgalaxies/gwave.html

http://www.usatoday.com/tech/science/space/2007-05-17-merging-black-holes_N.htm

Well, it seems I was wrong about the number crunch involved for a simulation, but I still can't see them bouncing off their event horizons. They aren't really. They're bouncing off each other's "surface" (whatever that means in a black hole) but from our outside point of view, it would look like the EH's just hit and rebounded-- I think. The amount of almost-escaped energy built up just inside the EH must be massive; maybe enough to have an effect on motion.

Fadingstar
2008-Mar-04, 07:06 PM
They aren't really. They're bouncing off each other's "surface" (whatever that means in a black hole) but from our outside point of view, it would look like the EH's just hit and rebounded-- I think. The amount of almost-escaped energy built up just inside the EH must be massive; maybe enough to have an effect on motion.

I understand what you're saying and can go with that. What we need is a camcorder on a very long pole! lol.

It's bad enough getting to grips with the dynamics of a single BH let alone two colliding.
One option could be that they rebound off each other, but not enough to be released from the influence of their own attraction, and so keep rebounding in smaller increments till merger does occur. The spinning top analogy in a bowl.
The release of energy would be immense with each collision, whether this would result in a slowing of spin (assuming spinning BH's), or rate of velocity of the BH itself through space-time I don't know.
And then the problem comes as to whether it is a head-on collision between BH's or a curving impact following the gravity wells, or even if it makes any difference either way. I think... I'll have another coffee!
What would be nice is to see is some observed data showing BH's moving apart when the rules of gravity say they should be moving towards each other.