A black hole is a region of spacetime where gravity prevents anything, including light, from escaping. Theoriticallly, black hole have many size, from microscopic even as big as a galaxy that we can see.
    Black hole formed when an object can't survive from the pressure power of their gravity itself. sometimes, it calles dying star. Many object, including sun, will never be a black hole. Sun's gravity  and earth's gravity are not strong enough to force atomic power or nuclear in theirselves to against the gravity. in the other hand, for the object which have a big mass, gravity is the winner. And now, so many pepole believe, if all of galaxy in this universe round the black hole at the galaxy centre.
greatest blackhole in our galaxy centre have four times sun mass and have absorbed particle around it periodically. until now, astronom had identified the position around 2.5 million supermassive blackhole.
    Scientist got a fact, black hole always do revolution, so it will be more active one day. Black hole mass will increase if they absorb all the things near them. If black hole absorb more stars and particles, so black hole's gravity will stronger because ionization force increase. Any black hole will continually absorb gas andinterstellar dust from its direct surroundings and omnipresent cosmic background radiation. This is the primary process through which supermassive black holes seem to have grown. similar process has been suggested for the formation of intermediate-mass black holes in globular clusters. Another possibility is for a black hole to merge with other objects such as stars or even other black holes. This is thought to have been important especially for the early development of supermassive black holes, which could have formed from the coagulation of many smaller objects. The process has also been proposed as the origin of someintermediate-mass black holes
    Black hole have 2 type, black hole which have rotation or not. The Kerr black hole, which is probably the most common form in nature, rotates because the star from which it was formed was rotating. When the rotating star collapses, the core continues to rotate, and this carried over to the black hole (conservation of angular momentum). The Kerr black hole has the following parts: Singularity – centre, Event horizon – door of the hole, Ergosphere - an area like an egg and absorb all around it, Limit Statics - limit between ergosphere and normally room. If an object enter the ergosphere, in this case can be thrown go out from the black hole and got energy from the black hole rotation.

    Even we can't see the black hole, black hole have 3 characteristic which can be measured. that are mass, electrons, and velocity of rotation. partices can't run away from black hole if it passes trough the distance which is close to the black hole. so, object which can keep the save distance with black hole, will be absorbed. But, black hole can't absorb particles which are far from it. greatest blackhole in our galaxy centre have four times sun mass and have absorbed particle around it periodically. until now, astronom had identified the position around 2.5 million supermassive blackhole. Now, our earth still in safe area. but, danger will come to earth if have distance 10mil, now distance between earth and sun 93 mil.