Could any one give me clear informations about 'Black Hole' in the Universe?

Answer 1

Try a google search to get dozens of links

Answer 2

Hello Bala:

Right now, since they are invisible, no one has ever seen a
black hole. There are many theories out there based upon the observed effects of black holes, but no clear information such as size, appearance, length, depth, shape, etc...So your guess is as good as the next I suppose.

There are those who will heap all kinds of suppositions onto your back about this and that possibility at or in a black hole.
My idea is that those things are all theories and awaiting further study.

Answer 3

when any mass creates gravitational field around it, all the matter pulled towards its center.
now, when the matter, has more dense atom, like ( say all 100% matter is dense metals like uranium or other radioactive-heavy metals), in the process of ccompaction due to gravity, towards the centre of planet, the densification takes place,
at such high level that,
the mass, which is producing gravitational pull,\
boosts its gravitational pull , due to increasing , incoming heavy atoms,

now, this process keep continuing, and after some durations, even the photons in lights can not escape from such gravitational pull,
hence, in optherwords, it attracts light also,

hence we can not see light , and so its black hole

Answer 4

A black hole is caused by a star that collapses in on its self

Answer 5

Here's NASA's introduction to black holes.

Answer 6

balck holes are at center of evry galaxy

they kik started star formation in glaxies

and they hungry for matter


cherrs

Answer 7

Try http://en.wikipedia.org/wiki/Black_hole

Answer 8

Read the earliest posts first, (at the bottom) then go to www.wikipedia.com and check out "gravastars", or "collapsars". Even professor Stephen Hawking, who wrote "A brief history of time", has since changed his mind, and no longer believes that the former concept of a "black hole" can exist in nature, because it is precluded by the laws of physics. Astrophysics- collapsars, or gravastars.
Although some currently [as we receive emissions which may have occurred many thousands of years ago] active collapsars provide us with evidence that they exist, from the streams of plasma ejected from their poles,we cannot ,with the technology we have at present, detect those emissions originating deep down in their gravitational wells. The reason being that such emissions have been gravitationally redshifted far into the radio spectrum, and the maximum wavelengths within our grasp at the moment are around a kilometre in length. We would need huge and prohibitively expensive space based interferometry to detect them.


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Saturday, June 17, 2006

astrophysics- collapsars

As those photons of electromagnetic energy which are directed away from the centre of the collapsar rise up from the intense gravitational well, they keep the same speed [the speed of light] but lose energy in the process. Their wavelength increases and frequency lowers. The change in frequency caused by the gravitational redshifting which occurs equals the product of the height gained and the gravitational field strength [which decreases as height is gained], divided by the square of the speed of light. Once you accept that matter moving at high speed can rise up to considerable heights from the inside of a Schwarzchild sphere or spheroid, before falling back in again [even though such unpowered objects cannot possibly reach the edge of the universe], it becomes exceedingly difficult to argue that light or other forms of electromagnetic radiation [ all moving at the speed of light ] cannot also rise up from inside such a sphere or spheroid, losing energy but maintaining lightspeed, provided that such photons of energy are directed away from the centre of the collapsar: any other photons will move along a path of increasingly curved spacetime until reaching the centre of the collapsar. So, if matter [carrying information] can rise up from the inside of what was formerly called an EVENT HORIZON [now a Schwarzchild sphere or spheroid], it cannot be a true horizon, only one that presently exists for us, here on Earth, because our technology has not yet advanced to the point where we can send multiple probes to the vicinity of a collapsar [formerly a BLACK HOLE]; electromagnetic energy can also rise up through a Schwarzchild sphere or spheroid. Such electromagnetic radiation, however, CAN reach us here on Earth, even though massively downshifted from their original high frequency/short wavelength gamma radiation, to low frequency/long wavelength redio waves.

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Saturday, June 10, 2006

astrophysics- collapsars

The situation regarding electromagnetic radiation is somewhat different. All types of electromagnetic radiation, from gamma rays to radio waves travel at the speed of light in space. The observations made by EDDINGTON and CROMMELIN in 1919 [which confirmed EINSTEIN'S theories and gave credibility to the concept of BLACK HOLES] showed that light rays are bent when passing nearby a massive body, such as a star. The more massive the body and the closer in, the more spacetime is curved, producing what appears to us to be a bending of the light rays. If a body becomes massive enough [which is the cutoff point between a large neutron star and a BLACK HOLE, or, more correctly, a collapsar] tangential light rays become bent to the extent that their path at its surface becomes circular. That would be the case if that body was not rotating; its surface would become a Schwarzchild sphere. If rotating, complications are involved, the faster it rotates, the more oblate it becomes, and it needs to become even more massive to produce a Schwarzchild spheroid, and [with the single exception of its equatorial plane] the path of such a light ray becomes non- circular. As the mass of such bodies continues to grow, its Schwarzchild sphere [ or, much more likely, spheroid ] moves up, and away from its surface. In both cases, at the surface of the spheroid or sphere, the escape speed at any point on it is the speed of light, and was referred to as its EVENT HORIZON.

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Sunday, June 04, 2006

astrophysics-collapsars

Although reasoning by analogy should always be regarded as being highly suspect, a good analogy can often help make clear a difficult subject: you decide whether the following is apt. The world's best thrower is at the bottom of a deep, wide, but dry well. Although supplied with a comprehensive collection of rocks, pebbles and stones of various sizes, that person is unable to throw even the tiniest pebble to a catcher waiting at the top of the well. Several small children, however, easily manage to accomplish that task with much larger stones, because they are spaced evenly on platforms constructed at suitable intervals on the wall of the well. The child at the bottom hurls a stone up to the first platform, where another child catches it and continues the process to the second platform, where yet another child catches it, and so on, finally being caught at the top. The situation is analogous to a probe located just inside the Schwarzchild sphere [formerly the EVENT HORIZON] of a non-rotating, supermassive collapsar [black hole] because, like the thrower who is unable to generate the speed required to reach the top of the well, the probe, whether using high speed electrons or something larger but slower, like bullets; those projectiles [having the property of mass] can never be accelerated to the speed of light and can therefore never reach the edge of the universe, or even close to it. but they can be propelled a useful distance to a point beyond the Schwarzchild sphere, where the material itself, or the information gained can be given another boost or, in the case of information, have its form changed into electromagnetic energy, for retransmission to us, whether we are located on Earth or in space.

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astrophysics-collapsars

The simplest subject to consider is a non-rotating, supermassive collapsar [black hole], since its Schwarzchild sphere [it would be a spheroid if rotating], also presently being referred to by some as an EVENT HORIZON, may be several light weeks from its centre, minimising the effects of elongation and compression experienced by a robustly constructed and highly powered probe, in free fall and with no radial velocity [speed] with respect to it. If that probe contained a linear accelerator firing a stream of electrons away from that centre at nearly the speed of light, when the probe is a fair distance away, those electrons may be configured in coded bursts to provide information, and at first would reach a great distance, perhaps light years, depending on their initial speed, distance from , and mass of the collapsar. As it approaches the Schwarzchild sphere the distance those electrons reach reduces, but even when the Schwarzchild sphere is passed, those electrons, travelling on a ballistic trajectory, still have the speed necessary to go back through the Schwarzchild sphere to reach a second probe, kept back some considerable distance and easily managing to maintain a stationary position, from which it can either decode or relay the information to us, either by radio or laser messaging. A non-rotating, supermassive collapsar avoids the tidal forces involved otherwise, but, because all stars so far observed have been found to be rotating, it is an almost sure bet that all naturally occuring collapsars will be found to rotate to some degree, but it is theoretically possible that a collision of collapsars or neutron stars can produce one with zero rotation. and, of course, a sufficiently technologically advanced civilisation could produce one, given enough time, simply by directing large amounts of matter at high speed, against the spin, at the equator of an already slowly rotating collapsar.

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Sunday, May 28, 2006

astrophysics-collapsars

Another point to bear in mind is that there is no reason why anything, powered or unpowered [on a ballistic trajectory ], can not receive a gravitational assist from any massive body in the vicinity, whether a planet or star, in exactly the same manner as our probes do; swinging by an intermediary to gain the necessary speed to accomplish its mission.

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Sunday, May 21, 2006

astrophysics-collapsars

SCHWARZCHILD also did not accept the existance of BLACK HOLES when ,in around 1916, he showed that , because the square of the escape speed of a massive body equals twice the product of its mass, M , multiplied by the gravitational constant, G ,divided by its radius, R . in the case of an extremely massive body, when combined with a small radius, the escape speed can be equal to, or greater than the speed of light. let's have a look at the definition, or meaning of escape speed. Derived from studies of ballistics, which, at the time referred to the trajectory of cannon or musket balls through Earth's gravitational field, but, in theory it is that speed at which an object must be moving at the surface of a massive body [such as a star or planet], such that at a distance of infinity it has zero kinetic energy[or no speed; that is, stationary]. These days, the edge of the universe is usually taken as being an acceptable distance. Note that the definition only refers to those things having the property of mass, which can never be accelerated to the speed of light, and not to electromagnetic energy, such as light, radio waves, gamma radiation, etc., which always move at the speed of light in space. Also note that only objects moving along ballistic trajectories are referred to, not rockets or anything else with a means of propulsion, because I intend to return to these points later.

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Sunday, May 14, 2006

astrophysics- collapsars

After MICHELSON and MORELY performed their famous experiment to precisely determine the speed of light, they then attempted a further experiment to discover Earth's speed through the ETHER, which was at the time believed to be the medium by means of which electromagnetic radiation is propagated, in much the same manner as air is the medium for the propagation of sound waves through the atmosphere. although they tried reconfiguring their apparatus, they kept getting the same figure, which they would no doubt have found somewhat perplexing. the speed of light through space is now known to be 299,792,458 metres/sec [much more accurate figures are being determined on a regular basis]. in the period 1905 to 1915, EINSTEIN published his SPECIAL and GENERAL theories of RELATIVITY, establishing that the speed of light through space is a constant, regardless of the speed of any observer [incidentally, he thought that such a phenomenon as a BLACK HOLE could not exist in reality, because it would mean that the speed of light at its equator would have to be exceeded due to the conservation of angular momentum, in the same manner as ice skaters are able to accelerate their rate of rotation by drawing their arms in towards their bodies