supernova explosions can outshine a galaxy. The outer layers of the explodingstar are blasted out in a radioactive cloud. This expanding cloud, visible longafter the initial explosion fades from view, forms a supernova remnant. So, ablack hole is an object, which is so compact that the escape velocity from itssurface is greater than the speed of light. The following table lists escapevelocities and Schwarzchild radii for some objects: The black hole massesranging from 4 to 15 Suns and are believed to be formed during supernovaexplosions. The after-effects are observed in some X-ray binaries known asblack hole candidates. The velocity depends on the mass of the planet. Thescientists believe if our Sun dies, the sun may turn into a black hole. Blackholes were theorized about as early as 1783, when John Michell mistakenlycombined Newtonian gravitation with the corpuscular theory of light . Theconcept of an escape velocity, Vesc, was well known, and even though thespeed of light wasn't, Michell's idea worked the same. He showed that Vescwas proportional to mass/circumference and reasoned that, for a compactenough star, Vesc might well exceed the speed of light. He had two mistakes: he subscribed to the corpuscular theory of light, and he assumed thatNewton's law of universal gravitation could apply to such a situation. Thesemistakes happened to cancel each other out, but when the wave theory oflight gained favor, the astronomers abandoned these dark stars. Also, therearent many physical features of a black hole. In an saying coined by JohnWheeler , "black holes have no hair," hair meaning surface features fromwhich details of it's formation might be obtained....
