In a fraction of a second, it should collapse to a point. No known force will stop it from shrinking to a point. This radius is called the Schwarzschild radius . Note how small this is. It is a radius of only 3 km for the Sun.
Black holes are even smaller than neutron stars.
Since light isn't going fast enough to escape, and nothing goes faster than light, nothing can escape. Once you cross the sphere at this radius, nothing can save you. This surface is called the event horizon. All the calculations done above were done using Newtonian gravity. We should use Einstein gravity.