[Gowtham Ravula]

Gowtham Ravula  asked the Naked Scientists:
   
Hi

My name is Gowtham and i have been a ardent listener of Naked Scientists for about an year and half. I love naked astronomy and here is my question:

When a "Super massive" black hole eats a "Big" black hole, will the big black hole start emitting energy as it collapses into Super massive black hole?

I will be glad if my question is answered. Thank you!

Thanks,
Gowtham

What do you think?

[graham.d]

Generally Black Holes will have an accretion disk of matter orbiting them. This will be radiating and if a BH encounters a much bigger BH it is likely that both their accretion disk will be subject to a great deal of turbulance and, comprising charged particles, will emit radiation. If we take two "perfect", non-rotating, non charged BHs (if any exist) then I assume they would not (could not) radiate in the electromagnetic spectrum. However, they will (I think) create gravitational waves. The two BH's behaviour will be complex during a collision process and the relatively simple maths applying to a spherically symmetric situation do not apply. It is a good question. Maybe someone with a greater knowledge than me can answer this.

[syhprum]

There are several computer simulations available on the internet to view.

[Soul Surfer]

The simulation shows what would happen if two black holes were already in a circular orbit around each other and the orbit is losing energy by gravitational radiation.  Achieving a circular orbit without significant "viscosity" to lose some energy as might be found in black holes with discs of matter circulating about them is almost impossible  this means that in most cases they would probably perform hyperbolic orbits around each other like comets and go on their way with a deflection in their directions of motion.  the probability that two black holes would hit each other is extremely small because they are so tiny remember that the diameter of a black hole is about one mile for every solar mass that they contain and even a one billion solar mass black hole is only the size of the orbit of Saturn or Uranus.

[syhprum]

Soul Surfer
It is an interesting point that you raise about the small size of stellar mass black holes, as all simulations start off with non rotating BH's in orbit, an incredibility unlikely scenario.
This may well be the reason why no gravity waves have been detected as yet as merging BH's are the only likely source.