Tuesday, November 17, 2009

what is a black hole in space universe astronomy galaxies event horizon speed of light

Simulated view of a black hole in front of the Large Magellanic Cloud. The ratio between the black hole Schwarzschild radius and the observer distance to it is 1:9. Of note is the gravitational lensing effect known as an Einstein ring, which produces a set of two fairly bright and large but highly distorted images of the Cloud as compared to its actual angular size.picture of black hole by Alain r (c) from wikipedia.org This file is licensed under the Creative Commons Attribution ShareAlike 2.5

In black hole have found out surplus of x-ray radiation
Astrophysicists managed to find out surplus in the high-energy x-ray radiation which is starting with galaxy NGC 1365. Article of scientists is accepted to the publication in magazine The Astrophysical Journal Letters, and its pre-print is accessible on site http://arxiv.org/abs/0909.2820

Galaxy NGC 1365 settles down on distance about 60 million light years from the Earth in constellation the Furnace. Within the limits of job scientists have carried out the analysis of the data collected by devices Suzaku, Swift and Integral. As a result they managed to find out that in range энергий above 2 kiloelectronvolt, quantity of photons at least on two order above the settlement.

The reasons of occurrence of surplus for scientists while aren't clear, however they have some hypotheses. So they believe that, probably, round hole there is second layer of matter which that intensively absorbs, and it is source of superfluous beams (the hole radiates nothing - for it the matter absorbed by object) answers. Other probable variants are the second black hole in vicinities of the first and unusual geometrical structure of vicinities of object.

More recently scientists managed to explain occurrence of high-energy x-ray photons in space beams. Source of these photons are regions intensive astration. These regions let out streams of the loaded particles which force interstellar gas to let out x-ray radiation.

In general relativity, a black hole is a region of space in which the gravity well is so deep that gravitational time dilation halts time completely forming an event horizon, a one-way surface into which objects can fall, but out of which nothing can come. It is called "black" because it absorbs all the light that hits it, reflecting nothing, just like a perfect black-body in thermodynamics. Quantum analysis of black holes shows them to possess a temperature and Hawking radiation.

Despite its invisible interior, a black hole can reveal its presence through interaction with other matter. A black hole can be inferred by tracking the movement of a group of stars that orbit a region in space which looks empty. Alternatively, one can see gas falling into a relatively small black hole, from a companion star. This gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation that can be detected from earthbound and earth-orbiting telescopes. Such observations have resulted in the scientific consensus that, barring a breakdown in our understanding of nature, black holes exist in our universe.
Event horizon
The defining feature of a black hole is the appearance of an event horizon; a boundary in spacetime beyond which events cannot affect an outside observer. As predicted by general relativity, the presence of a mass deforms spacetime in such a way that the paths particles take tend towards the mass. At the event horizon of a black hole this deformation becomes so strong that there are no more paths that lead away from the black hole. Once a particle is inside the horizon, moving into the hole is as inevitable as moving forward in time (and can actually be thought of as equivalent to doing so).

To a distant observer clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect (known as gravitational time dilation) the distant observer will see an object falling into a black hole slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational red shift. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon.

For a non rotating (static) black hole, the Schwarzschild radius delimits a spherical event horizon. The Schwarzschild radius of an object is proportional to the mass. Rotating black holes have distorted, nonspherical event horizons. Since the event horizon is not a material surface but rather merely a mathematically defined demarcation boundary, nothing prevents matter or radiation from entering a black hole, only from exiting one. The description of black holes given by general relativity is known to be an approximation, and it is expected that quantum gravity effects become significant near the vicinity of the event horizon. This allows observations of matter in the vicinity of a black hole's event horizon to be used to indirectly study general relativity and proposed extensions to it.
Though black holes themselves may not radiate energy, electromagnetic radiation and matter particles may be radiated from just outside the event horizon via Hawking radiation.

info (c) wikipedia.org