What is blackhole?

Question

universe

Answer 1

Black is the end stage of any star when a big star die .It convert into back hole . black hole is small bu ole it very heavy .the weight of 1cm2 area of black hole is  around 10000 kg. we can't see the back hole by any telescope . no body never see the black hole yet. Because due to high mass/cm2 black hole has very high gravitational power so nothing from the black hole. light is also the high gravitational power black hole absorbed light also . so, we can not see the black hole

Answer 2

An extremely dense mass, having so much gravity that even light can not escape it's gravitational pull.

Answer 3

a blackhole is a place where is extreme gravity and force.this part always remains invisible.it is sail to form due to a supernova caused by the bursting of stars at the end of their life.

Answer 4

Black is hole like government of a nation which swallow every thing without any output.

Answer 5

black hole is a dead star......which has a dense mass .....with a high gravitational force.. This pulls every body moving in the space towards itself. Even the light energy reaching the black hole will be fully absorbed.

Answer 6

What is a black hole?

A black hole is a region of spacetime from which nothing can escape, even light.

To see why this happens, imagine throwing a tennis ball into the air. The harder you throw the tennis ball, the faster it is travelling when it leaves your hand and the higher the ball will go before turning back. If you throw it hard enough it will never return, the gravitational attraction will not be able to pull it back down. The velocity the ball must have to escape is known as the escape velocity and for the earth is about 7 miles a second.

As a body is crushed into a smaller and smaller volume, the gravitational attraction increases, and hence the escape velocity gets bigger. Things have to be thrown harder and harder to escape. Eventually a point is reached when even light, which travels at 186 thousand miles a second, is not travelling fast enough to escape. At this point, nothing can get out as nothing can travel faster than light. This is a black hole.

It is now believed that at the center of each galaxy there is a super-massive black hole that is millions to billions of times heavier than our sun. The massive black hole captures nearby stars and drags them into a swirling accretion disk. A "torus" in the inner accretion shields the black hole in those systems that are viewed edge on (which is probably the case for our galactic center). In many of these systems (which are called AGN = active galactic nucleus), a jet is ejected perpendicular to the disk and is seen in the optical and radio wavebands. In the very central regions the disk becomes so hot (tens of millions of degrees) that the emission is in the X-ray and Gamma-ray bands. This animation shows an artist's impression of the view from an approaching spaceship. The HEASARC data archives contain many observations of these systems made with orbiting X-ray and Gamma-ray observatories.

Answer 7

1) The term "black hole" is sometimes used to refer to an imaginary place where objects, files, or funds go when they get lost for no apparent reason.

2) In physics and astronomy, a black hole is a region in time and space within which gravity is so strong that nothing can escape, not even electromagnetic radiation such as visible Light. Black holes are thought to surround certain celestial objects.

The idea of a black hole (if not the term itself) is not new. As the intensity of the gravitational field around an object increases, so does the escape velocity. The escape velocity for a celestial mass (such as a star, planet, or moon) is the vertical speed with which an object must be hurled from the surface in order to fly forever beyond the gravitational influence of the mass. If a substantial celestial body such as a star becomes small enough in diameter, the escape velocity at the surface can theoretically exceed the velocity of light. This idea occurred to astronomers even in Isaac Newton's time. Modern astronomers believe they have observed black holes, consisting of stars that have collapsed under their own gravitation after spending their nuclear fuel. Black holes are also believed to exist at the centers of galaxies, including our own.

A black hole produces bizarre effects on time and space. As seen from outside, an object falling into a black hole would approach the so-called event horizon, which is a spherical "one-way membrane" or "Rubicon" surrounding the black hole itself. If the object were a clock, it would seem to run more and more slowly as it approached the event horizon, and would never quite make it inside the black hole. From the reference frame of the falling object, nothing out of the ordinary would take place in the rate at which time passed, and the entry to the black hole would proceed apace, although the gravitational force near the event horizon might tear the falling object apart.

Black holes have been fodder for wild ideas and science-fiction stories since the concept became well known in the mid-1900s. Some scenarios are sensational to the point of madness. For example, suppose a tiny black hole, manufactured for use as a doomsday weapon, were dropped onto the surface of the earth? It would, as the story goes, proceed to devour the planet with unstoppable and phenomenal violence.

Answer 8

A black hole is a region of space in which the gravitational field is so powerful that nothing, not even light, can escape its pull after having fallen past its event horizon. The term "Black Hole" comes from the fact that, at a certain point, even electromagnetic radiation (e.g. visible light) is unable to break away from the attraction of these massive objects. This renders the hole's interior invisible or, rather, black like the appearance of space itself.

Despite its interior being invisible, a black hole may reveal its presence through an interaction with matter that lies in orbit outside its event horizon. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center. Alternatively, one may observe gas (from a nearby star, for instance) that has been drawn into the black hole. The 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.[2][3][4] Such observations have resulted in the general scientific consensus that—barring a breakdown in our understanding of nature—black holes do exist in our universe.[5]

The idea of an object with gravity strong enough to prevent light from escaping was proposed in 1783 by the Reverend John Michell[6], an amateur British astronomer. In 1795, Pierre-Simon Laplace, a French physicist independently came to the same conclusion.[7][8] Black holes, as currently understood, are described by Einstein's general theory of relativity, which he developed in 1916. This theory predicts that when a large enough amount of mass is present in a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, preventing all matter and radiation within it from escaping.

While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event horizon at the outer edge, the description changes when the effects of quantum mechanics are taken into account. Research on this subject indicates that, rather than holding captured matter forever, black holes may slowly leak a form of thermal energy called Hawking radiation.[9][10][11] However, the final, correct description of black holes, requiring a theory of quantum gravity, is unknown.

Answer 9

the leftover gravity from a collapsed star.

Answer 10

a blackhole is a rip in the space time fabric, caused by a star going supernova

Answer 11

A collapsed star that has reached critical mass. Critical mass means that the structure of the star is in sufficient to stand up to the intense gravitational forces that are occuring as the planet collapses in on it self. Because of the intense gravity, all matter and mass is sucked into the hole  and is recognized by the ecretion disk that forms around the gravitational plane known as the event horizon. Nothing can escape a black hole, not even light. In fact, that is how they spot the black holes in space, by identifying the tidal pulls that are taking place on the stars  next to them as they are slowly being sucked into the black hole. Oh, happy day.

Answer 12

A black hole is a situation of a dying star that has lot of energy and any object that enters the event horizon, a point of no escape, of the dying star can never escape from entering into black hole. This is a day in and day out incidences happening in the distant space, which we are not aware of it unless we read science related novels like " A Brief history of Time" written by Stephen Hawking. Even our Sun, which is a star eventually become a black hole and we all would inevitably enter the event horizon and skewed by the gravity of the Black Hole. This will give us an answer for whether there exists a so called God.

Answer 13

Its a point of singularity where intense gravitation forces pull matter to it.

This point of singularity is caused by the explosive death of a star. There are normally three options, one is that the left over matter may remain cosmologically inactive and turn into a white dwarf, then there is a possibility where the explosion may be so gigantic that it may leave a point of intense gravity, and then there's the possibility of a red giant, all this occurs after a supernovae.

Answer 14

its a star that is so dense that the gravity it gives off is so strong that it swallows up light also...so therefore there is no light escaping...hence a BLACK hole...

Answer 15

A black hole is an object in space so dense that nothing can escape its gravitational pull, not even light.

No one knows much else about them.  Some people theorize that the matter sucked into a black hole gets spewed out of a white hole in another dimension.  Other people theorize it just gets super compressed.

Answer 16

Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a " singularity ". As the density increases, the path of light rays emitted from the star are bent and eventually wrapped irrevocably around the star. Any emitted photons are trapped into an orbit by the intense gravitational field; they will never leave it. Because no light escapes after the star reaches this infinite density, it is called a black hole.

But contrary to popular myth, a black hole is not a cosmic vacuum cleaner. If our Sun was suddenly replaced with a black hole of the same mass, the earth's orbit around the Sun would be unchanged. (Of course the Earth's temperature would change, and there would be no solar wind or solar magnetic storms affecting us.) To be "sucked" into a black hole, one has to cross inside the Schwarzschild radius. At this radius, the escape speed is equal to the speed of light, and once light passes through, even it cannot escape.

Answer 17

hello,

A black hole is a region of space in which the gravitational field is so powerful that nothing, not even light, can escape its pull after having fallen past its event horizon. The term "Black Hole" comes from the fact that, at a certain point, even electromagnetic radiation (e.g. visible light) is unable to break away from the attraction of these massive objects. This renders the hole's interior invisible or, rather, black like the appearance of space itself.

Despite its interior being invisible, a black hole may reveal its presence through an interaction with matter that lies in orbit outside its event horizon. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center. Alternatively, one may observe gas (from a nearby star, for instance) that has been drawn into the black hole. The 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.[2][3][4] Such observations have resulted in the general scientific consensus that — barring a breakdown in our understanding of nature— black holes do exist in our universe.[5]

The idea of an object with gravity strong enough to prevent light from escaping was proposed in 1783 by the Reverend John Michell[6], an amateur British astronomer. In 1795, Pierre-Simon Laplace, a French physicist independently came to the same conclusion.[7][8] Black holes, as currently understood, are described by Einstein's general theory of relativity, which he developed in 1916. This theory predicts that when a large enough amount of mass is present in a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, preventing all matter and radiation within it from escaping.

While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event horizon at the outer edge, the description changes when the effects of quantum mechanics are taken into account. Research on this subject indicates that, rather than holding captured matter forever, black holes may slowly leak a form of thermal energy called Hawking radiation.[9][10][11] However, the final, correct description of black holes, requiring a theory of quantum gravity, is unknown.

Black hole types

The simplest possible black hole is one that has mass but neither charge nor angular momentum. These black holes are often referred to as Schwarzschild black holes after the physicist Karl Schwarzschild who discovered this solution in 1915. It was the first (non-trivial) exact solution to the Einstein equations to be discovered, and according to Birkhoff's theorem, the only vacuum solution that is spherically symmetric. For real world physics this means that there is no observable difference between the gravitational field of such a black hole and that of any other spherical object of the same mass —for example a spherical star or planet— once you are in the empty space outside the object. The popular notion of a black hole "sucking in everything" in its surroundings is therefore incorrect; the external gravitational field, far from the event horizon, is essentially like that of ordinary massive bodies.

More general black hole solutions were discovered later in the 20th century. The Reissner-Nordström solution describes a black hole with electric charge, while the Kerr solution yields a rotating black hole. The most general known stationary black hole solution is the Kerr-Newman metric having both charge and angular momentum. All these general solutions share the property that they converge to the Schwarzschild solution at distances that are large compared to the ratio of charge and angular momentum to mass (in natural units).

While the mass of a black hole can take any (positive) value, the other two properties —charge and angular momentum— are constrained by the mass. In natural units , the total charge Q and the total angular momentum J are expected to satisfy Q2+(J/M)2 ≤ M2 for a black hole of mass M. Black holes saturating this inequality are called extremal. Solutions of Einstein's equation violating the inequality do exist, but do not have a horizon. These solutions have naked singularities and are thus deemed unphysical. The cosmic censorship hypothesis states that it is impossible for such singularities to form in due to gravitational collapse. This is supported by numerical simulations.[citation needed]

Black holes forming from the collapse of stars are expected —due to the relatively large strength of electromagnetic force— to retain the nearly neutral charge of the star. Rotation, however, is expected to be a common feature of compact objects, and the black-hole candidate binary X-ray source GRS 1915+105[18] appears to have an angular momentum near the maximum allowed value.

Sizes!!

Black holes occurring in nature are commonly classified according to their mass, independent of angular momentum J. The size of black hole as determined by the radius of the event horizon, or Schwarzschild radius, is proportional to the mass  through  where  is the Schwarzschild radius and  is the mass of the Sun. Thus size and mass have a simple relationship, which is independent of rotation. According to this mass/size criterion then, black holes are commonly classified as:

Supermassive black holes that contain hundreds of thousands to billions of Solar masses are believed to exist in the center of most galaxies, including our own Milky Way. They are thought to be responsible for active galactic nuclei, and presumably form either from the coalescence of smaller black holes, or by the accretion of stars and gas onto them. The largest currently suspected supermassive black hole is located in OJ 287 weighing in at 18 billion solar masses.[19]

Intermediate-mass black holes, whose sizes are measured in thousands of solar masses, probably exist. They have been proposed as a possible power source for the ultra-luminous X ray sources. There is no known mechanism for them to form directly, so they most probably form via collisions of lower mass black holes, either in the dense stellar cores of globular clusters or galaxies. Such creation events should produce intense bursts of gravitational waves, which may be observed in the near- to mid-term. The boundary limit between super- and intermediate-mass black holes is a matter of convention. Their lower mass limit, the maximum mass for direct formation of a single black hole from collapse of a massive star, is poorly known at present.

Stellar-mass black holes have masses ranging from a lower limit of about 1.5-3.0 solar masses (the Tolman-Oppenheimer-Volkoff limit for the maximum mass of neutron stars) up to perhaps 15—20 solar masses, and are created by the collapse of individual stars, or by the coalescence (inevitable, due to gravitational radiation) of binary neutron stars. Stars may form with initial masses up to ~100 solar masses, or possibly even higher, but these shed most of their outer massive layers during earlier phases of their evolution, either blown away in stellar winds during the red giant, AGB, and Wolf-Rayet stages, or expelled in supernova explosions for stars that turn into neutron stars or black holes. Being known mostly by theoretical models for late-stage stellar evolution, the upper limit for the mass of stellar-mass black holes is somewhat uncertain at present. The cores of still lighter stars form white dwarfs.

Micro black holes (also mini black holes) have masses much less than that of a star. At these sizes the effects of quantum mechanics are expected to come into play. There is no known mechanism for them to form via normal processes of stellar evolution, but certain inflationary scenarios predicted their production during the early stages of the evolution of the universe. According to some theories of quantum gravity they may also be produced in the highly energetic reaction produced by cosmic rays hitting the atmosphere or even in particle accelerators such as the Large Hadron Collider. The theory of Hawking radiation predicts that such black holes will evaporate in bright flashes of gamma radiation. NASA's GLAST satellite, to be launched in 2008, will search for such flashes as one of its scientific