A couple questions about black holes, gamma ray bursts, hawking radiation, etc.?

Question

from my understanding, when a black hole is formed and it has a lot of material to "eat" it will begin rapidly pulling it in and somewhere along the way the black hole begins to fire high energy rays out of its north and south poles. what causes this?

Also, if my information is correct, black holes evaporate by releasing hawking radiation back into the universe, is this radiation always emitted at a specific rate depending on the size of the black hole, or can the rate vary? and if it can vary is there anyway it could be manipulated?

Answer 1

I noticed nobody else has yet answered your question about Hawking Radiation. What others have said about the creation of the accretion disk and polar blackhole jets is basically all true, so I won't bother explaining that over again. It's a fairly well-known and understood process, and not mysterious at all, as some people have said.



Hawking Radiation is based on two variables, temperature and the mass of the blackhole. The bigger the blackhole is the lower it's temperature is, and the smaller it is, the higher it's temperature is. This is the equation for Hawking radiation (http://is.gd/9ElEHl):



T = ((h bar) c^3)/(8 pi k G M) |

M | mass

T | temperature

(h bar) | reduced Planck constant (~~ 1.054572×10^-34 J s)

c | speed of light in vacuum (~~ 2.998×10^8 m/s)

k | Boltzmann constant (~~ 1.38065×10^-23 J/K)

G | Newtonian gravitational constant (~~ 6.67×10^-11 m^3/(kg s^2))



The equation looks daunting, but it's actually pretty simple, there's only two variables in there, the T and the M, everything else is a constant. For example, the temperature of a black hole that weighs the same as the Sun would be 6.171×10^-8 K, or just a tiny fraction above absolute zero. Whereas a blackhole that weighs the same as an average person (72 kg) would have a temperature of 1.704×10^21 K! So as you can see the smaller it is, the hotter it is.



Now, there's something interesting about its temperature relationship: large blackholes cannot evaporate via Hawking Radiation because their temperature is below the Cosmic Background Temperature of 2.725K (http://is.gd/tZ9jGd). So really big blackholes will always be feeding on the latent left-over energy of the universe's Big Bang itself. As the universe expands, this background temperature goes down, and eventually at some point it will reach temperature ranges of these black holes, and at that point the black holes will begin to evaporate by Hawking Radiation. Right now, a black hole that is exactly balanced with this Cosmic Temperature, neither feeding on the radiation nor adding more radiation to it, would have a mass about 60% of that of Earth's Moon. We don't know of any black holes that are smaller than about 3 solar masses, quite a bit bigger than 60% Lunar masses; so as far as we know, no actual blackhole in this universe are emitting Hawking Radiation, as they would be too big to emit it.

Answer 2

It is actually not fully known what causes the polar jets of a black hole with an accretion disk. They originate just outside the event horizon, where shredded matter is spiraling in at near the speed of light. The energy produced by friction is greater than any other known source, converting as much as 40% of matter to energy. The resulting explosive outburst is likely directed along the poles because the accretion disk itself provides resistance, especially near the event horizon. The forces taking place there are probably very complex, and definitely very powerful.

Answer 3

They do not "pull" - mass falls in.

The Black Hole is rotating rapidly (conservation of angular momentum as the Super Nova core shrinks down to a Black Hole.

Infalling matter entrains with the rotation and obstructs matter - a disc of infalling matter rotating around the equator of the Black Hole forms. This infalling spiral heats and emits radiation.



The magnetic field of the pre-collapse core also survived and shrank with the core - so you have a rapidly rotating magnetic field - this contains much of the radiation which escapes from the North and South magnetic poles.

Answer 4

THE ACCRETION DISK AND THE MAGNETIC FIELD PRODUCE THE JETS JUST OUTSIDE THE EVENT HORIZON.

The hawking radiation is determined by the mass inside the event horizon, so it can't be manipulated.