What type of star is formed when the core of a massive star undergoes gravitational collapse at the end of its life?

The formation of a neutron star occurs when the core of a massive star, typically one that has a mass greater than about three times that of our Sun, undergoes gravitational collapse at the end of its life cycle. During this process, the outer layers of the star are expelled in a supernova explosion, while the core collapses under immense gravitational pressure. As the core contracts, protons and electrons combine to form neutrons, resulting in an incredibly dense sphere made primarily of neutrons. This transformation is critical because it marks a distinct endpoint in the life cycle of a massive star, leading to significantly different properties compared to less massive stars, which may end their lives as white dwarfs.

In contrast, star clusters refer to groups of stars that are gravitationally bound, while binaries involve pairs of stars that orbit around a common center of mass. Double stars are similar but are more generally used to describe two stars that are close together in the sky, regardless of whether they are gravitationally bound. None of these options describe the specific process that leads to the formation of a neutron star following the gravitational collapse of a massive star's core. Thus, the correct answer is indeed that a neutron star forms from such a collapse.