The key difference between a supernova explosion and a black hole is the nature of their gravitational collapse. Let's delve into the details:
When a massive star goes supernova, it undergoes a catastrophic collapse and explosion. The core of the star collapses under its own gravity, reaching extreme densities and temperatures. This collapse generates an outward pressure wave that causes the outer layers of the star to be ejected in a powerful explosion. The energy produced in the supernova is immense and can be strong enough to overcome the gravitational pull of the remaining stellar remnant, such as a neutron star or a black hole. As a result, some of the stellar material can escape the gravity well.
On the other hand, a black hole forms when a massive star undergoes a gravitational collapse beyond a certain threshold known as the Schwarzschild radius. The Schwarzschild radius depends on the mass of the collapsing object. For a given mass, the Schwarzschild radius defines the boundary within which the object's gravitational pull becomes so strong that nothing, including light, can escape from it. This region is what we refer to as the event horizon of a black hole.
Once an object collapses within its Schwarzschild radius and forms a black hole, its gravity becomes extremely strong due to the tremendous density and compression of matter. Anything that passes beyond the event horizon of a black hole is effectively trapped, and no known physical process can enable it to escape.
So, while a supernova explosion can generate enough energy to overcome the gravitational pull of a massive star, the gravitational collapse of matter within the event horizon of a black hole creates conditions where escape becomes impossible. The fundamental nature of space and time is drastically altered within a black hole, resulting in an intense gravitational field that prevents anything from escaping, including light itself.