Black hole........................

Black hole is an end point in the space having very high gravitational force that can attracts even a whole planet inside it. Black hole nothing but a star of more than about three times the mass of sun whose nuclear fuel is completely burnt, that star turns into a black hole. This black hole is independent of matter from which it is produced. Every thing it attracts is sent to the existing surface called horizon. The horizon is an ideal one way membrane even light cannot escape from it. So it is said as black hole being dark space.
The formation of black holes depends on the matter and mass of star. The cold matter can be stable but their mass must be considerably less than that of Sun. To be masses in the compared to solar mass, there should be two configurations. The first, the white dwarf, is supported against gravitational collapse by the same quantum forces that keep atoms from collapsing. However, these forces cannot support a star which has a mass in excess of about 1.2 solar masses. The second stable configuration, the neutron star, is supported against gravitational collapse by the same forces that keep the nucleus of an atom from collapsing. Between 1 and 3 solar masses there is maximum mass of neutron star.
If the dying star does not eject the matter then it turns to black hole. But there is no the existence of star which ejects matters and does not become black hole. Most of the star which is in the stage of dying cannot eject mass to decrease their 3 solar mass limits. The number of black hole is increasing accordingly in the universe. It is interesting to know that the black hole once formed would not decay easily and loose its weight even on emitting the thermo radiation. It is because on radiation energy is lost and therefore mass is also lost, a black hole can shrink and decay if radiating is faster than accumulating. But the ambient radiation incident on black hole from stars is larger than thermal radiation emitted by black hole. So the time for decaying of black hole too much longer than the life of universe. So it is unpredictable the age of once formed black hole. Something’s in the life cannot be seen through our naked eyes but can be feel. For example- emotion is such a thing we cannot see but feel. Same is the case for black hole. It cannot be seen but its effect on other matter can be seen. Same is the case of binary x-ray system Cygnus X-I. There are a number of binary x- ray systems known. The data which is a fairly normal star is in mutual orbit about a very compact object. Mass flows from the star to an accreting disk about the compact object. This heats up frictional force. The matter heats to a temperature at which thermal x-rays are produced. Only neutron star and black hole can accomplish this thermal temperature. Some of the binary x-rays indicate the neutron star.
In the case of three binary x-rays, Cygnus X-1, LMC X-3, and A0620-00, the typical mass of the compact body is about 10 solar masses which is too much than any neutron star. According to assumptions and laws given by many scientists no other body exist having such a huge mass except black hole, which proves its existence. This evidence is less direct and more model- dependent, it is sure that the black hole exists somewhere at the cores of nuclei of active galaxies. Black hole attracts everything that is close to it and emits radiation. This radiation is an energy source for ultra luminous objects. The presence of black hole does not gives spectacular radiation even it is present in nuclei of active galaxies. In Milky Way Galaxy a star of 2*106 solar masses is present in a region so compact that no explanation other than that of central black hole is feasible. Similar, although less convincing, observations of the presence of central black holes have been made for several nearby galaxies. The existence of super massive black holes is virtually certain.
We can say that the black hole is nothing but a star whose mass is 3 times the mass of sun. Sometime we can see black hole and its ability in science fiction films and some cartoons too. It attracts everything that comes beside it. There may be a black hole in our galaxy too. But there is no sign and scientist say that there is no possibility of black hole in our galaxy.