Ergosphere: Making a black hole work

News Excerpt:

Rotating black holes (a.k.a. Kerr black holes) have a unique feature: a region outside their outer event horizon called the ergosphere.

What is an Ergosphere?

Just beyond the Event horizon sphere, a rotating black hole will also have a bigger sphere that an object can enter and then leave if it’s moving fast enough, but still less than the speed of light.

  • The ergosphere is the region wherein the spacetime continuum has been deformed.
  • The term ‘ergosphere’ comes from ‘ergon’, the Greek word for ‘work’. It is so named because it is possible to extract matter and energy from the ergosphere.
  • It’s possible to explain the effects of gravity outside the ergosurface using Newtonian physics. But inside it, the theories of relativity are needed.

  • Some scientists have suggested using this possibility to send an object into the ergosphere and allow it to accelerate there along the black hole’s direction of rotation so that it comes out moving faster. This energy ‘gain’ will translate to the black hole losing some angular momentum.

Event Horizon:

  • It is a boundary marking the limits of a black hole. At the event horizon, the escape velocity is equal to the speed of light. 
  • Since general relativity states that nothing can travel faster than the speed of light, nothing inside the event horizon can ever cross the boundary and escape beyond it, including light. 
  • Thus, nothing that enters a black hole can get out or can be observed from outside the event horizon.

Black Hole:  It is formed when a massive star runs out of fuel to fuse, and blows up, leaving its core to implode under its weight to form a black hole.

Gravitational Singularity: The center of a black hole is a gravitational singularity, a point where the general theory of relativity breaks down, i.e. where its predictions don’t apply.

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