Celestial+Objects+in+Space

Black Holes
A black hole is a theoretical region of space in which the gravitational field is so powerful that nothing,not even electromagnetic radiation(e.g. visible light),can escape its pull after having fallen past its event horizon. The term derives from the fact that the absorption of visible light renders the hole's interior invisible,and indistinguishable from the black space around it. 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 e.g.,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.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. The idea of an object with gravity strong enough to prevent light from escaping was proposed in 1783 by John Michell,an amateur British astronomer.In 1795,Pierre-Simon Laplace, a French physicist independently came to the same conclusion.Black holes, as currently understood,are described by the general theory of relativity.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.

It Is impossible to escape from black holes !
Popular accounts commonly try to explain the black hole phenomenon by using the concept of escape velocity, the speed needed for a vessel starting at the surface of a massive object to completely clear the object's gravitational field. It follows from Newton's law of gravity that a sufficiently dense object's escape velocity will equal or even exceed the speed of light. Citing that nothing can exceed the speed of light they then infer that nothing would be able to escape such a dense object.However, the argument has a flaw in that it does not explain why light would be affected by a gravitating body or why it would not be able to escape. Nor does it give a satisfactory explanation for why a powered spaceship would not be able to break free. Two concepts introduced by Albert Einstein are needed to explain the phenomenon. The first is that time and space are not two independent concepts, but are interrelated forming a single continuum,spacetime.This continuum has some special properties. An object is not free to move around spacetime at will; it must always move forward in time and cannot change its position in space faster than the speed of light. This is the main result of the theory of special relativity. The second concept is the base of general relativity; mass deforms the structure of this spacetime. The effect of a mass on spacetime can informally be described as tilting the direction of time towards the mass. As a result, objects tend to move towards masses. This is experienced as gravity. This tilting effect becomes more pronounced as the distance to the mass becomes smaller. At some point close to the mass, the tilting becomes so strong that all the possible paths an object can take lead towards the mass.This implies that any object that crosses this point can no longer get further away from the mass, not even using powered flight. This point is called the event horizon.