General Relativity – Does an Accelerating Charged Black Hole Emit EM Radiation?

black-holeselectromagnetismgeneral-relativityquantum mechanics

I have read this question:

Charged particle is accompanied with EM radiation (has field that falls with distance as 1/r) when it moves with acceleration.

Does a constantly accelerating charged particle emit EM radiation or not?

It emits light, because it "stirs up" the electromagnetic field. To understand this, just dip your finger into a still pond and move it in a circle. Water waves will emanate from your finger. These waves have energy, which means energy is being taken away from you. Same goes for the charges.
In fact, this follows almost automatically from the finite propagation speed of light. The electric field of a stationary charge obeys Coulomb's law. If the charge suddenly starts moving, the field won't obey Coulomb's law anymore, but it can't instantly change everywhere because of the finite propagation speed. Instead a "shockwave" of information goes out from the charge at speed c. This shockwave contains electromagnetic energy and travels at the speed of light — it is light.

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Why does an accelerated charge radiate away energy?

So based on these, two things come to mind:

  1. all accelerating charges emit EM radiation (because they stir up the field)

  2. nothing can escape a black hole (neither should the EM radiation)

And I cannot reconcile these two at the same time, because if light (EM radiation) cannot escape the black hole, then how does it emit it if it is accelerating?

Question:

  1. Does an accelerating charged black hole emit EM radiation?

Best Answer

Yes, it will radiate. The light does not come from inside the black hole. The accelerated charge of the black hole affects the electromagnetic field around but outside the event horizon.

You could ask the same question you are asking now about gravitational waves. Binary black hole systems radiate gravitational waves, even though a gravitational wave that fell into a black hole could not escape.

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