Black hole creation?

Black holes occur when the gravity of a star is so strong, that enormous energy must be used to throw the object off it. But when you give it that much energy, that increases the gravitational attraction, so the energy is not enough. If the object is a black hole, then you can never win: more energy always increase the attraction so much that the object will not leave.

We could turn the sun into a black hole if we squeezed all of its mass into a sphere with radius 3 km (about the size of Berkeley). Such squeezing does take place in a supernova explosion, and we think that the celestial xray emitter called "Cygnus X-1" is such a black hole. Xrays are emitted by particles falling into the black hole.

We could turn the earth into a black hole if we squeezed all of its mass into a sphere with radius 1 cm.

We also believe that the center of the Milky Way galaxy contains a black hole, as well as the center of many other galaxies. This is a relatively recent discovery, and we do not yet know how they were formed

Thank you for your reply bio_man,I did not know that energy can increase gravity attraction.One last question: Is black hole constantly gaining mass by sucking the matter in,thus making its gravity stronger every second? If it does,than is there some limit? Can a black hole gain gravity and mass limitless? That would mean that the one black hole in center of our milky way will eventualy suck all stars and planets,including our earth in?

Interesting question, but it can't be known if the earth will ever be destroyed by a blackhole. Certainly our sun could never become one as it does not have sufficient mass. Since the sun is a star. As some stars do when they die, they could turn into a blackhole. So the sun, when it dies, could possibly turn into a blackhole.