What happens to the star at the end of the red giant phase?

At the end of the red giant phase, a star undergoes significant changes depending on its mass. For low to intermediate-mass stars, the outer layers are expelled, forming a planetary nebula, while the core contracts and ultimately becomes a white dwarf. In more massive stars, nuclear fusion continues to create heavier elements until an iron core forms, leading to a supernova explosion. This explosion can leave behind a neutron star or a black hole, depending on the initial mass of the star.