What do we call an object in space with gravity so strong that not even light can escape?

An object in space with gravity so strong that not even light can escape is known as a black hole. This occurs because a black hole's gravitational pull is extremely intense, created by the collapse of a massive star at the end of its lifecycle. Once this gravitational field becomes stronger than the escape velocity of light, it leads to the phenomenon where light itself cannot escape, rendering the black hole invisible and detectable only through its interactions with surrounding matter.

In contrast, a neutron star is the remnants of a supernova explosion and is incredibly dense but does not have the same gravitational pull as a black hole. A supernova is an explosive event signaling the death of a star, and while it can lead to the formation of a black hole, it does not possess the specific characteristics associated with these objects. A red supergiant is a phase in a star's life cycle prior to a supernova and is characterized by its large size and brightness, but again, it does not have the properties that define a black hole.