we all know that black holes absorbs everything include photons which travels at the speed of 3,00,000 kms. it is capable to absorbs such fastest particle , so from this shall we conclude that black hole is perfect black body. every researchers believe this before the hawking discovered hawking radiation. in order to understand hawking radiation first of all we need to know how black hole function and what is event horizon in black hole.
EVENT HORIZONS
In astrophysics , event horizon is a boundary beyond which events cannot affect the observer.
The event horizon is the boundary defining the region of space around a black hole from which nothing (not even light) can escape. In other words, the escape velocity for an object within the event horizon exceeds the speed of light.
The defining feature of a black hole is the appearance of an event horizon—a boundary in spacetime through which matter and light can pass only inward towards the mass of the black hole. Nothing, not even light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine whether such an event occurred.
At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole.
To a distant observer, clocks near a black hole would appear to tick more slowly than those further away from the black hole. Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow as it approaches the event horizon, taking an infinite time to reach it. so, from this we come to know about science behind event horizons
But, in what way this event horizon is related to hawing radiation?
These hawking radiations are the kind to black body thermal radiations, this happens due to the quantum effect occurs near the event horizons. the quantum effects are explained at end of the articles . the black holes with greater mass have lesser hawking radiation and vice versa so smaller black holes shrinks faster by emitting greater hawking radiations.
Emission process of hawking radiation
Hawking radiation arises from the steady conversion of quantum vacuum fluctuations into pairs of particles, one of which escaping at infinity while the other is trapped inside the black hole horizon.
Physical insight into the process may be gained by imagining that particle–antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being boosted by the black hole's gravitation into becoming real particles. As the particle–antiparticle pair was produced by the black hole's gravitational energy, the escape of one of the particles lowers the mass of the black hole. this is reason behind shrinkage of black holes . so, this is also called evoparation of black holes.
The subatomic particle pair photons nutrino (some other massively sub atomic particle) naturally orginate from beyond the event horizon. for now we are not clear about what kind of particle does hawking radiation contains.
Does black holes emits x rays?
The X-rays come from hot gas orbiting around the black hole in an accretion disk. As the gas orbits, magnetic stresses cause it to lose energy and angular momentum, thus spiraling slowly in towards the black hole. The orbital energy is transformed into thermal energy, heating up the gas to millions of degrees, so it then emits black body radiation in the X-ray band.
a short summary of this article
Hawking radiations are originate beyond the event horizon,
but no particle beyond the event horizons escape. before event horizon a particle with velocity greater than the escape velocity of the black hole my escape from the black hole so, we conclude that the x ray originate from the hot disk of accerlated gas have velocity greater then escape velocity and it is before the event horizon
many researchers believes that negative particles fall back into black holes
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