White dwarfs are stellar corpses supported by electron degeneracy pressure. With no fusion, they slowly cool over billions of years, transitioning from blue-white to red, eventually becoming invisible "black dwarfs."
Unlike normal stars, white dwarfs are held up by quantum mechanical pressure from tightly packed electrons obeying the Pauli exclusion principle. This prevents further gravitational collapse.
Chandrasekhar Limit: 1.4 M☉