What happens to a star when all the helium has been used up?

When a star exhausts its helium fuel, it can no longer sustain nuclear fusion in its core, leading to a series of significant changes. The core contracts under gravity, causing it to heat up, while outer layers may expand, transforming the star into a red giant. Depending on the star's mass, it may eventually undergo further fusion of heavier elements or shed its outer layers to form a planetary nebula, leaving behind a white dwarf. More massive stars may explode as supernovae, leaving behind neutron stars or black holes.