Is a black hole hot or cold?

Question

are there different kinds of black hole with different temperatures?

Answer 1

The answer discovered By Steven Hawking depends on the size of the black hole. The larger the black hole the colder it is. Typical Black Holes are incredibly cold. To be hot the black hole would need to be almost microscopic, very very small anyway.

The temperature is the result of what is now called Hawking Radiation. Which is produced by quantum tunneling near the event horizon.

A black hole of one solar mass has a temperature of only 60 nanokelvins; in fact, such a black hole would absorb far more cosmic microwave background radiation than it emits. A black hole of 4.5 × 10²² kg (about the mass of the Moon) would be in equilibrium at 2.7 kelvins, absorbing as much radiation as it emits. Yet smaller primordial black holes would emit more than they absorb, and thereby lose mass.

Answer 2

The Question
(Submitted November 11, 1997)

What is the temperature of a black hole?


The Answer
The temperature of a black hole is determined by the 'black body radiation temperature' of the radiation which comes from it. (e.g., If something is hot enough to give off bright blue light, it is hotter than something that is merely a dim red hot.)
For black holes the mass of our Sun, the radiation coming from it is so weak and so cool that the temperature is only one ten-millionth of a degree above absolute zero. This is colder than scientists could make things on Earth up until just a few years ago (and the invention of of a way to get things that cold won the Nobel prize this year). Some black holes are thought to weigh a billion times as much as the Sun, and they would be a billion times colder, far colder than what scientists have achieved on Earth.

However, even though these things are very cold, they can be surrounded by extremely hot material. As they pull gas and stars down into their gravity wells, the material rubs against itself at a good fraction of the speed of light. This heats it up to hundreds of millions of degrees. The radiation from this hot, infalling material is what high-energy astronomers study.

David Palmer
for Ask an Astrophysicist

Answer 3

Stephen Hawking seems to say that Black Holes are really really small(me personally I don't think they are, but that's just me), like 10^-30. Addressing the hot or cold question; since heat is really a description of the kinetic/vibrational energy of the particles under consideration, the question becomes one of how much the particles in the black hole can vibrate and/or move. On the one hand, with tremendous quantities of matter falling into the black hole, it would seem that there would be huge amounts of kinetic energy available to heat the center mass. On the other hand, with everything collapsing to (maybe) zero volume size, and gravity reaching near infinity, the particles may simply get pulled into a fixed energy matrix that doesn't allow for vibration; yielding a cold center. The excess energy escapes via the mechanisms so beautify described by Hawking.

Answer 4

Interesting question. Except for the minuscule Hawking Radiation, they are not "hot" as far as an outside observer is concerned. And if they were hot on the inside, it would beg the question of the limits of that temperature, and if the limits approached infinity, then one would think the black hole would eventually explode. No, I think they are extra-dimensional at the singularity, where "hot' and "cold" have no meaning because the matter would no longer be baryonic. Of course, that last sentence is just a wild guess. That's all anybody's got -- a wild guess.

Answer 5

Temperatures of stars is measured with its spectrum
A black hole does not show a spectrum (no light at all).
So the temperature of a black hole can't be measured.
So far practical. Now theoretical.
A black hole is a star. Most stars are much hotter than earth.
So a black hole is probably much hotter than earth.

Th

Answer 6

Both. Hot and cold air are merged in the black hole.

Answer 7

My hypothesis would be hot for the fact that black holes have enough gravity that light can't escape, so on that basis, I think heat cannot escape black holes either. It pulls in the heat and holds it there until it becomes "spaghettified" (If I remember correctly from physics class...) and compacted.

Answer 8

I am of the opinion that it is hot since matter in the accretion disk gets very hot as it falls closer and closer to the black hole

Answer 9

black holes are generally cold

Answer 10

Chances are they are cold because of the distance from the sun.