Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar (19 October 1910 – 21 August 1995) was an Indian-American astrophysicist. He shared the 1983 Nobel Prize in Physics "for his theoretical studies of the physical processes of importance to the structure and evolution of the stars." His mathematical treatment of stellar evolution yielded many of the current theoretical models of the later evolutionary stages of massive stars. The Chandrasekhar limit describes the maximum mass of a white dwarf (1.44 solar masses). Above it, a stellar remnant will collapse to form a neutron star or black hole. Many concepts, institutions and inventions, including the Chandra X-Ray Observatory, are named after him.

Born in the late British Raj, Chandrasekhar worked on a wide variety of problems in physics during his lifetime, contributing to the contemporary understanding of stellar structure, white dwarfs, stellar dynamics, stochastic process, radiative transfer, the quantum theory of the hydrogen anion, hydrodynamic and hydromagnetic stability, turbulence, equilibrium and the stability of ellipsoidal figures of equilibrium, general relativity, mathematical theory of black holes and theory of colliding gravitational waves. At the University of Cambridge, he developed a theoretical model explaining the structure of white dwarf stars that took into account the relativistic variation of mass with the velocities of electrons that comprise their degenerate matter. Chandrasekhar revised the models of stellar dynamics first outlined by Jan Oort and others by considering the effects of fluctuating gravitational fields within the Milky Way on stars rotating about the galactic center. His solution to this complex dynamical problem involved a set of twenty partial differential equations, describing a new quantity he termed "dynamical friction", which has the dual effects of decelerating the star and helping to stabilize clusters of stars. Chandrasekhar extended this analysis to the interstellar medium, showing that clouds of galactic gas and dust are distributed very unevenly.