1983 Nobel Prize in Physics(1)
Reason for Award
for his theoretical studies of the physical processes of importance to the structure and evolution of the stars (Philos. Mag. 11 (1931) 592; Astrophys. J. 74 (1931) 81; Astrophys. J. 96 (1942) 161)
Laureates
United States of America
Explanation
Stars in space change their shapes and brightness as they live and age. Mr. Chandrasekhar calculated how heavy an old, shrinking star can be before it collapses. This threshold is called the “Chandrasekhar limit” and is about 1.4 times the mass of our Sun. A star lighter than that limit becomes a small, bright white dwarf. A heavier star keeps collapsing and can turn into a neutron star or even a black hole. His work is like a cosmic map that tells us the future of every twinkling star we see.
Related Keywords
white dwarf
A white dwarf is the dense remnant left when a Sun-like star exhausts its fuel. It packs nearly a solar mass into a volume comparable to Earth’s, yielding densities of tonnes per cubic centimeter. The star is supported by quantum degeneracy pressure of electrons, with no active fusion inside. Its light comes from residual thermal energy and fades slowly over billions of years. Chandrasekhar’s theory accurately links its mass to its tiny radius.
Chandrasekhar limit
The Chandrasekhar limit is the maximum mass a white dwarf can stably support, approximately 1.4 solar masses. Beyond this threshold electron degeneracy pressure fails, and the star collapses into a neutron star or black hole. The limit sets the trigger for Type Ia supernovae, making it essential for cosmic distance measurements. Its derivation required melding special relativity with Fermi statistics, a bold step in the 1930s. Observations now reveal many white dwarfs whose masses cluster near this critical value.
quantum degeneracy pressure
Quantum degeneracy pressure arises from the Pauli exclusion principle, which forbids identical fermions from occupying the same quantum state. Even at low temperature the particles possess high kinetic energy, so the pressure differs from ordinary thermal pressure. In white dwarfs electrons, and in neutron stars neutrons, provide this support. The competition between degeneracy pressure and gravity allows stars to exist at extreme densities. Chandrasekhar extended the pressure formula into the relativistic regime.
radiation pressure
Radiation pressure is exerted when photons transfer momentum to matter; in very hot luminous stars it can rival gravity. Including it in stellar structure equations yields accurate energy balance descriptions. In compact objects like white dwarfs it is usually a minor correction, yet near the mass limit it becomes significant. Chandrasekhar incorporated the radiative term, refining the mass-radius relation. Today radiation pressure remains vital in models of massive stars and supernova explosions.
stellar evolution
Stellar evolution describes the entire life cycle of a star from formation to final remnant. The path depends strongly on mass: low-mass stars end as white dwarfs, massive ones as neutron stars or black holes. Nuclear fusion inside produces new elements, and supernova explosions spread them through the cosmos. Chandrasekhar’s critical mass establishes a branching point, giving the theory a quantitative anchor. This sharpened interpretations of the H-R diagram and refined galactic chemical-evolution models.
neutron star
A neutron star forms when a stellar core whose mass exceeds the Chandrasekhar limit collapses. Only about 20 km across, it contains more mass than the Sun. The interior is supported by neutron degeneracy pressure and is expected to exhibit superfluidity and superconductivity. Many neutron stars emit radio pulses as pulsars due to strong magnetic fields and rapid rotation. Chandrasekhar’s calculations first hinted that such exotic objects must exist.