The Nobel Prize in Physics was awarded to Subrahmanyan Chandrasekhar in 1983 "for his theoretical studies of the physical processes important in the structure and evolution of stars".

He was recognized for his work on the evolution of stars, particularly:

* The Chandrasekhar limit: This limit describes the maximum mass a white dwarf star can have before collapsing into a neutron star or black hole.

* The theory of stellar structure and evolution: He developed mathematical models to understand how stars evolve over time, from their formation to their eventual demise.

So while Chandrasekhar didn't "pioneer" the study of stellar evolution (others like Arthur Eddington had made significant contributions), his work was groundbreaking and earned him the Nobel Prize.