1.what is black hole?2.what is chandrasekhara limit?

Question

i want more information with figures

Answer 1

1. Black hole is a "mass" of an indefinite density, so it's gravity force is immeasurable. It is so strong that it keeps everything inside ait and "sucks" all nearby matter inside, even the light has no chance of avoiding it, unless it passes it by at a very small angle and at some distance, when it is somewhat deflected, but it's pathway is severely curved.

Black holes are the last stadium of a star "death". High density is an aftermath of the star's mass condensation in a tiny volume, because of gravity force remained after all nuclear fuel was exausted. Stars mainly consist of hydrogen, that releases energy when it is fusioned in helium. Released energy cause mass defect, absorbing neutrones from environment, so the created molecule of helium has considerably greater mass than hydrogen molecules that created it. Thus the density of the product is enlarged, while helium molecules that were not able to absorb neutrons disassebmle in fission reaction, providing additional energy for continuation of the process.

2. Not all stars end up like black holes. Only heavy ones. The boundary value for the star mass that determines whether the star will end like neutron star or like black hole is called the Chandrasekhara limit and it's value is 1.47 mass of the Sun. It means that stars of lesser mass end their lives like neutron stars, high density stellar objects of a very small size (couple of kilometers in diameter, or even smaller). Heavier stars, after exausting all fuel, explode like NOVA, releasing excessive mass away. The remaining core has enough energy to continue fusion at slower pace, enlarginig density and finally creating black hole.

Black hole is considered as "singularity" - very special phenomenon in space-time, which can be regarded as an ultimate end of the local space-time. But since the unverse is infinite, there will always be enough matter to be sucked in the black hole, and still to remain enough for continuity of the life of universe.

Some calculations say that black hole can eventually get "fed-up", i.e. saturated with the sucked matter, when it can turn into the "white hole", or the source of matter, instead of it's grave, but it is not practically proved yet.

Answer 2

something where all the laws of physics are useless


1.A black hole is defined to be a region of space-time where escape to the outside universe is impossible. The outer boundary of this region is called the event horizon. Nothing can move from inside the event horizon to the outside, even briefly, due to the extreme gravitational field existing within the region. For the same reason, observers outside the event horizon cannot see any events which may be happening within the event horizon; thus any energy being radiated or events happening within the region are forever unable to be seen or detected from outside. Within the black hole is a singularity, an anomalous place where matter is compressed to the degree that the known laws of physics no longer apply to it.


Black hole can be defined as a region in space with a gravitational field so powerfful that even electromagnetic radiations (even light) can't escape from it. It can be of any size an d its mass can be between that of sun to many million times the mass of sun....
Chandrasekhara Limit :
This limit describes the maximum mass of a white dwarf star or equivalently the minimum mass for which a star will ultimately collapse into a neutron star or black hole after a supernova explosion.

Answer 3

Black hole can be defined as a region in space with a gravitational field so powerfful that even electromagnetic radiations (even light) can't escape from it. It can be of any size an d its mass can be between that of sun to many million times the mass of sun....
Chandrasekhara Limit :
This limit describes the maximum mass of a white dwarf star or equivalently the minimum mass for which a star will ultimately collapse into a neutron star or black hole after a supernova explosion.

Answer 4

A black hole is a very massive and dense object, so much so that light cannot escape. Black holes are usually formed by dying stars, more massive than our Sun.
The Chandrasekhar limit gives the minimum mass needed for a star to become a neutron star or a black hole at the end of its life.
This limit is about 1.44 solar masses.

Answer 5

1.A black hole is defined to be a region of space-time where escape to the outside universe is impossible. The outer boundary of this region is called the event horizon. Nothing can move from inside the event horizon to the outside, even briefly, due to the extreme gravitational field existing within the region. For the same reason, observers outside the event horizon cannot see any events which may be happening within the event horizon; thus any energy being radiated or events happening within the region are forever unable to be seen or detected from outside. Within the black hole is a singularity, an anomalous place where matter is compressed to the degree that the known laws of physics no longer apply to it.

Answer 6

A black hole is the last stage of a star.
Briefly, at first a massive star becomes a red giant star where it appears very red. In RED GIANT stage, when the hydrogen atoms (H) gets collide they explodes and light & heat emits off it. In RED GIANT stage, the star will expand millions of time of its original size. When Hydrogen atoms almost gets vanished then it contracts to a very large extent and becomes a WHITE DWARF, where it appears relatively dim. Then it becomes a BLACK HOLE. The density of a black hole will be very high, that even a teaspoon of it may weigh about millions of tonnes. If any thing is moving near the BLACK HOLE, it attracts. No thing can get away from it.
CHANDRA SHEKHAR limit states that to become a BLACK HOLE from a WHITE DWARF, the star's mass should be 1.4 times the solar mass.

Answer 7

The earth 's gravity is such that a satellite would orbit [ignoring the atmosphere] at the surface at about 7 miles per second.
If you pushed the speed above that it would spiral away from earth.
The orbital velocity at the surface of a black hole is calculated to be the speed of light. [Calculated by Chand etc.]
Nothing can go faster than the speed of light so the consensus it that nothing,not even light can escape.

Answer 8

You may consider it as a big depository out in space with tremendous gravitational pull that pull or tries to pull every thing that's near by.

The more stuff it accumulates the more mass it acquires more gravitational pull it achieves.

A white dwarf star's maximum density limit was calculated by an Indian astronomer, Sri. Chandrasekhara.

Answer 9

i think u hav enough information as to black holes.
the chandrashekhar limit is named after this indian astronomer (Mr. chandrashekhar) who calculated the maximum density of a white dwarf star. you can get more information about the chandrashekhar limit on any astronomical website.

Answer 10

Loosely speaking, a black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. Since our best theory of gravity at the moment is Einstein's general theory of relativity, we have to delve into some results of this theory to understand black holes in detail, but let's start of slow, by thinking about gravity under fairly simple circumstances.
Suppose that you are standing on the surface of a planet. You throw a rock straight up into the air. Assuming you don't throw it too hard, it will rise for a while, but eventually the acceleration due to the planet's gravity will make it start to fall down again. If you threw the rock hard enough, though, you could make it escape the planet's gravity entirely. It would keep on rising forever. The speed with which you need to throw the rock in order that it just barely escapes the planet's gravity is called the "escape velocity." As you would expect, the escape velocity depends on the mass of the planet: if the planet is extremely massive, then its gravity is very strong, and the escape velocity is high. A lighter planet would have a smaller escape velocity. The escape velocity also depends on how far you are from the planet's center: the closer you are, the higher the escape velocity. The Earth's escape velocity is 11.2 kilometers per second (about 25,000 m.p.h.), while the Moon's is only 2.4 kilometers per second (about 5300 m.p.h.).

Now imagine an object with such an enormous concentration of mass in such a small radius that its escape velocity was greater than the velocity of light. Then, since nothing can go faster than light, nothing can escape the object's gravitational field. Even a beam of light would be pulled back by gravity and would be unable to escape.

The idea of a mass concentration so dense that even light would be trapped goes all the way back to Laplace in the 18th century. Almost immediately after Einstein developed general relativity, Karl Schwarzschild discovered a mathematical solution to the equations of the theory that described such an object. It was only much later, with the work of such people as Oppenheimer, Volkoff, and Snyder in the 1930's, that people thought seriously about the possibility that such objects might actually exist in the Universe. (Yes, this is the same Oppenheimer who ran the Manhattan Project.) These researchers showed that when a sufficiently massive star runs out of fuel, it is unable to support itself against its own gravitational pull, and it should collapse into a black hole.

In general relativity, gravity is a manifestation of the curvature of spacetime. Massive objects distort space and time, so that the usual rules of geometry don't apply anymore. Near a black hole, this distortion of space is extremely severe and causes black holes to have some very strange properties. In particular, a black hole has something called an 'event horizon.' This is a spherical surface that marks the boundary of the black hole. You can pass in through the horizon, but you can't get back out. In fact, once you've crossed the horizon, you're doomed to move inexorably closer and closer to the 'singularity' at the center of the black hole.

You can think of the horizon as the place where the escape velocity equals the velocity of light. Outside of the horizon, the escape velocity is less than the speed of light, so if you fire your rockets hard enough, you can give yourself enough energy to get away. But if you find yourself inside the horizon, then no matter how powerful your rockets are, you can't escape.

The horizon has some very strange geometrical properties. To an observer who is sitting still somewhere far away from the black hole, the horizon seems to be a nice, static, unmoving spherical surface. But once you get close to the horizon, you realize that it has a very large velocity. In fact, it is moving outward at the speed of light! That explains why it is easy to cross the horizon in the inward direction, but impossible to get back out. Since the horizon is moving out at the speed of light, in order to escape back across it, you would have to travel faster than light. You can't go faster than light, and so you can't escape from the black hole.

(If all of this sounds very strange, don't worry. It is strange. The horizon is in a certain sense sitting still, but in another sense it is flying out at the speed of light. It's a bit like Alice in "Through the Looking-Glass": she has to run as fast as she can just to stay in one place.)

Once you're inside of the horizon, spacetime is distorted so much that the coordinates describing radial distance and time switch roles. That is, "r", the coordinate that describes how far away you are from the center, is a timelike coordinate, and "t" is a spacelike one. One consequence of this is that you can't stop yourself from moving to smaller and smaller values of r, just as under ordinary circumstances you can't avoid moving towards the future (that is, towards larger and larger values of t). Eventually, you're bound to hit the singularity at r = 0. You might try to avoid it by firing your rockets, but it's futile: no matter which direction you run, you can't avoid your future. Trying to avoid the center of a black hole once you've crossed the horizon is just like trying to avoid next Thursday.

Incidentally, the name 'black hole' was invented by John Archibald Wheeler, and seems to have stuck because it was much catchier than previous names. Before Wheeler came along, these objects were often referred to as 'frozen stars.' I'll explain why below.