What is the main event that triggers a type-2 supernova?

The main event that triggers a type-2 supernova is a massive core's rapid implosion followed by an explosion. This process occurs in massive stars, those that have significantly more mass than our Sun. As these stars evolve, they undergo nuclear fusion, synthesizing heavier elements in their core until they form an iron core. Iron is unique in that fusing it does not release energy; instead, it requires energy. When the core becomes predominantly iron, it can no longer support the weight of the outer layers.

As gravitational forces overcome the internal pressure from nuclear fusion, the core collapses violently, leading to an implosion. This rapid collapse causes the outer layers of the star to rebound and subsequently explode outward in what is observed as a type-2 supernova. This explosive event is immensely powerful and can outshine entire galaxies for a short duration, releasing a significant portion of the star's mass and energy into space, often leaving behind a neutron star or black hole.

Options related to white dwarf stars and the merger of gas into black holes describe different astronomical phenomena. The collision of galaxies is also a significant event in cosmic evolution but is not directly related to the mechanism of a type-2 supernova, which is distinctly associated with the lifecycle of