What is the average temperature of a black hole

Black body temperature, Hawking radiation, and consequences The emission mechanism of a black hole is a very complex process that was first theorised by Stephen Hawking. Kb is the Boltzmann constant; in SI units, its value is 1.

G is the universal gravitational constant with a value of 6. M is the black hole mass, which, due to their typical size in the universe, is commonly expressed in solar masses. People also viewed…. Books vs e-Books The books vs e-books calculator answers the question: how ecological is your e-book reader? Books vs e-Books Calculator. Cutoff frequency Use the cutoff frequency calculator to work out the cutoff frequencies of different filter circuits.

Cutoff Frequency Calculator. Flat vs. But that's just the temperature of the Hawking radiation. Because of the infinite gravitational time dilation. The thing to understand is that temperature is a measure of motion.

A hot gas is one where the molecules are, on average, moving faster than in a cold gas. See the Wikipedia temperature article and note this: "The coldest theoretical temperature is absolute zero, at which the thermal motion of all fundamental particles in matter reaches a minimum". Gravitational time dilation means things are moving slower. When the gravitational time dilation is infinite, things aren't moving at all.

This is why the black hole was originally known as the frozen star. Robert Wald said much the same in black hole physics. The black hole is said to have an effective temperature by virtue of Hawking radiation, but as Fraser Cain said, it's very low. More importantly, Hawking radiation is said to be emitted from outside the event horizon. So it isn't actually the temperature of the black hole.

Just as "the accretion disk that surrounds a BH can be very hot indeed" but it isn't actually the temperature of the black hole. Black holes do radiate, see Hawking radiation. And the more matter they absorb, the colder they get. For a black hole to evaporate, energy has to completely escape from its potential well. To make a rather crude analogy, if we fire a rocket from the surface of the Earth then below the escape velocity the rocket will eventually fall back.

The rocket has to have a velocity greater than the escape velocity to completely escape the Earth. When we are considering a black hole, rather than the escape velocity we consider the gravitational red shift. The red shift reduces the energy of any outgoing radiation, so it reduces the energy of any radiation emitted by the hotter vacuum state near the event horizon. If the red shift is infinite then the emitted radiation gets red shifted away to nothing and in this case there will be no Hawking radiation.

If the red shift remains finite then the emitted radiation still has a non-zero energy as it approaches spatial infinity. Steinhauer is physicist at Technion-Israel Institute of Technology. To make the black hole, his team used ultracold atoms of rubidium. The team chilled them to nearly the point at which they would be absolutely still.

Absolute zero occurs at The atoms were in gas form and very far apart. Scientists describe such a material as a Bose-Einstein condensate. With a little nudge, the team set the chilled atoms flowing. In this state, they prevented sound waves from escaping. That mimics how a black hole prevents the escape of light.

But black holes can let a bit of light slip out at their edges. Sometimes, quantum mechanics says, particles can appear in pairs. Those particles appear out of seemingly empty space.

Normally, the pairs of particles immediately destroy one another. If one particle falls into the black hole, the other can escape. That escaping particle becomes part of the stream of particles that comprise Hawking radiation.

In a sonic black hole, a similar situation occurs. The information you enter will appear in your e-mail message and is not retained by Phys.

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By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use. As with most galaxies, a supermassive black hole lies at the heart of NGC Credit: Davide de Martin. Provided by Universe Today. Citation : How cold are black holes?

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