What happens at the end of a star's life?

The medium-sized stars are the low mass stars that eventually become white dwarfs; the massive stars eventually explode (form a supernova); the high mass stars eventually form neutron stars; the very massive stars form blackholes; the supernova forms new nebula where star birth occurs.

At the end of a star's life, its fate depends on its mass. Low to medium-mass stars, like the Sun, will eventually exhaust their nuclear fuel and undergo a series of changes, culminating in the shedding of their outer layers to form a planetary nebula. The core that remains becomes a white dwarf, gradually cooling over billions of years. High-mass stars, however, undergo a more violent process, leading to a supernova explosion, which can leave behind either a neutron star or a black hole, depending on the mass of the core remaining after the explosion.