What happens when a black hole evaporates?
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ETpro (
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July 6th, 2013
Because they emit Hwaking radiation from their event horizon, black holes separated from a continuous source of new mass to eat do eventually starve and die. Read more about the phenomenon, if you are interested. Because mass dilution via Hawking radiation is such a slow process, even the smallest primordial black holes would have survived for most of the life of this universe. In fact, with tools like NASA’s NuSTAR and very large land-based radiotelescopes available, we are only now likely to be observing the death throes of black holes. Supermassive black holes would have to remain isolated from new mass for something like 10 to the 100th power years to disappear; something that will not occur before the Universe reaches heat death from entropy. So our Milky Way Galaxy’s supermassive black hole is safe from starvation for the time being. But die they do. So, when they do die, do black holes go out with a bang or a whimper?
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The black hole, no matter what size, will slowly decrease in mass until it reaches the microscopic scale.
The supermassive black hole will eventually become a micro black hole. These tiny black holes also undergo Hawking radiation. They will continue to emit Hawking radiation until they reach the Planck mass, which is the smallest possible mass of a black hole (21.7651 µg).
Black holes have something called “temperature,” which is dependent on the mass of the black hole. The higher the temperature, the more Hawking radiation is released and the faster it evaporates. The smaller the mass of the black hole, the higher the temperature. This forms a feedback loop, with the evaporation accelerating.
Once the black hole is reduced to the size of the Planck mass, however, Hawking radiation doesn’t work. The calculations break down. To be specific, the temperature becomes so hot that any Hawking radiation released will have the same mass as the black hole.
It is believed that once black holes reach this tiny size of the Planck mass, they never go away. They are too small to either absorb more mass or to release Hawking radiation.
The universe is alive. As a black hole disintegrates it creates a new universe on the other side this universe. At least that is what I heard on TV so it must be right. It is likely that our feable tiny little pinpoint brain are not capable of understanding such a phenomenon.
@PhiNotPi Excellent answer and fascinating link. Thanks.
@gondwanalon Pinpoint brain? I’ll have you know that my brain is considerably larger than the 22 µg of smallest black hole. In fact, it exhibits other black-hole like phenomena as well. For instance, have you seen any light escaping from my brain? I think not!
Also, if Planck-mass black holes do indeed remain in a stable state, they are a possible candidate for a WIMP (weakly interacting massive particle), which may be partly responsible for the effects of so-called “dark matter.”
The Planck mass is several orders of magnitude larger than the mass of typical subatomic particles:
2.17651 × 10^-5 grams is the mass of the smallest black holes
1.67262178 × 10^-24 grams is the mass of a proton
These means that when you add together all of the micro black holes in the universe, the combined mass could become very large, because each individual black hole weighs quite a bit (comparatively speaking, of course).
It vanishes in a puff of logic.
@PhiNotPi Thank you. It does my heart good to know that WIMPs may be responsible for holding the known Universe together.
@Rarebear I like that answer, even though it leaves much to be desired logically.
@ETpro it’s an obscure hitchhiker s guide reference.
@ETpro In fact, I shone a flashlight into your left ear and I DID see light coming out of the other ear. I’d say your brain is evaporating pretty quickly!
@Dutchess_III Ha. Just slipped past my event horizon. I’m still as dense as ever!
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