MPG: On the deceleration behaviour of black holes

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MPG: On the deceleration behaviour of black holes

Post by bystander » Fri Jun 04, 2010 11:53 pm

On the deceleration behaviour of black holes
Max Plank Institute for Gravitational Physics - 2010 June 04
Researchers use the concept of "anti-kick" to explain why the speed suddenly decreases after the collision of such exotic objects

Kicking is not only associated with football: if two black holes approach each other so closely as to collide and merge, the resulting black hole recoils and then races through the universe at a speed of up to several thousand kilometres per second. Sometimes, however, it experiences a sudden decrease in speed - a behaviour for which there was no convincing explanation. Scientists from the Max Planck Institute for Gravitational Physics have now found a solution to the puzzle: there is a type of recoil in the opposite direction that reduces the speed of the whole system. In this "anti-kick" the black hole emits gravitational waves to reach its energetically optimum shape: a sphere. (Physical Review Letters, June 3, 2010)
  1. Image
    Kicking about in space: Researchers have modeled the collision of black holes (1).
    Thereby it was shown that the newly created black hole is initially deformed (2).
    To smooth this asymmetry and achieve the energetically more favorable spherical
    shape, more momentum is radiated upwards: this "anti-kick" decelerates the black
    hole slightly -- it now continues to move with reduced speed (3).

    (MPI for Gravitational Physics) (Images and movies)

Understanding the "anti-kick" in the merger of binary black holes

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