Black hole का dark truth

Black holes in orbit around a normal star are detected from the earth due to the fricitional heating of infalling gas into the black hole, which can reach temperature greater than 10^(6)K . Assuming that the infalling gas can be modelled as a blackbody radiator, then the wavelenght of maximum power lies

Scientists suspect the presence of black hole (a body whose gravitational force is so strong that nothing can escape from its surface (not even light)) in our universe. Find the condition for a uniform spherical body to be a black hole.

A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass =5.98xx10^(24)kg ) have to be compresed to be a black hole?

The dimensions of the area A of a black hole can be written in terms of the universal gravitational constant G, its mass M and the speed of light c as A=G^(alpha)M^(beta)c^(gamma) . Here -