what are the causes of black holes?..why ?..when do they occur?

Answer 1

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.

There is quite a bit of black hole theory out there. For more information on it, try these books:


Black Holes and Warped Spacetime - William J. Kaufmann, III
Lonely Hearts of the Cosmos - Dennis Overbye
Black Holes and Time Warps, Einstein's Outrageous Legacy - Kip S. Thorne
The Mathematical Theory of Black Holes - S. Chandrasekhar
Black Holes and Baby Universes and other Essays - Stephen Hawking
Universe - William J. Kaufmann, III
Black Holes and the Universe - Igor Novikov

Answer 2

When you get a lot of matter in the one place, it will collapse under its own gravity. If there is enough matter, even the forces within atoms won't be enough to keep the matter apart and it will all fall inwards until all the matter occupies a single point with no size. The matter is concentrated at this point.

The force of gravity will be infinite at this point, causing the universe to bend in a strange way, resulting in a black hole:

1. light won't be able to escape because space is bent into a circle. That's why they're black.

2. matter close to the hole will be torn apart and almost all of it will be sucked into the hole to join the compressed matter at the centre of the hole.

3. A very small amount of energy will escape from the hole, and the hole will get smaller slowly, so that over trillions of years it will reduce and eventually disappear. The smaller the hole the faster it "evaporates". A really small hole the mass of say a mountain would disappear in about a second, ending in a blinding flash of light.

Answer 3

A black hole is because of a large sun collapsing. The steady increase of the sun collapse accelerates mass to the speed of light,the more the mass increases due to gravity.When it obtains the speed of light the mass increases to infinity. They happen in the center of a Galaxy which provides the gravity well large enough to be 10 to 100 light years across.

Answer 4

A black hole is the remains of a collapsed star.

A star is a fusion nuclear reaction and when it runs out of Hydrogen it explodes or collapses.

Answer 5

black holes freely moving bodies in space they will b havin enormous gravity that they can even attract bodies at certain kilometers.
according noble laurate chandrashekar these r all formed due redution of its mass by 1.44 to its original mass.
there is nothing like that it should bcome black holes only even they may bcome white dwarfs also.
but the condition to bcome white dwarf or blackhole is that,
if the star is mush bigger than our sun at maximum it will bcome blackhole otherwise if it is small it may bcome white dwarf.
our sun will also b white dwarf at last when its weight reduces by 1.44 to its original weight.

Answer 6

Black holes are gaps in ozone layer occured by pollution.