What type of celestial event can lead to the formation of black holes?

The explosion of a supernova is a critical process that can lead to the formation of black holes. When a massive star exhausts its nuclear fuel, it can no longer maintain the outward pressure needed to counterbalance the gravitational force acting on it. As a result, the star collapses under its own gravity, and if the remaining mass after the supernova explosion exceeds a certain limit (known as the Tolman-Oppenheimer-Volkoff limit), this implosion can lead to the formation of a black hole.

During a supernova explosion, the outer layers of the star are expelled into space, and the core may compress to such an extent that it creates a region of spacetime with gravitational pull so intense that not even light can escape from it. This is the defining characteristic of a black hole.

The other options involve phenomena that do not possess the necessary conditions to produce black holes. The constant burning of a star refers to its stable nuclear fusion process, and while it is essential for the lifecycle of stars, it does not lead to the formation of black holes. The merging of planets doesn't provide the immense gravitational forces required for black hole formation; likewise, the cooling of a planet pertains to the thermal evolution of planetary bodies rather than stellar processes