Chandrasekhar (1931): White dwarfs are supported by electron degeneracy pressure — the Pauli exclusion principle forbids two electrons sharing the same quantum state. As mass increases, electrons become relativistic and the pressure-density relation softens from P∝ρ⁵′³ to P∝ρ⁴′³. At the Chandrasekhar limit MCh ≈ 5.83/μₑ² M☉ ≈ 1.44 M☉, this pressure can no longer support the star — collapse to a neutron star or Type Ia supernova follows.