Stellar evolution occurs when a star loses its energy from continuous nuclear fusion reactions, causing instability due to decreasing gas pressure. In order to maintain stability, the star burns fuel in its core until it is depleted, causing the core to collapse into, depending on whether the star is low- or high-mass, either a dense white dwarf, a neutron star, or a black hole.
Why do stars evolve?
Why do stars tend to form in groups?
Stars tend to form in groups because of where star formation occurs. Stars form within a molecular cloud, where protostars begin to take shape in areas rich in molecular gases and dust. If they accumulate enough mass in these star-forming regions, some stars are pulled toward each other by gravity, forming pairs, multiple systems, or star clusters.
