Indian-American astrophysicist Subrahmanyan Chandrasekhar showed that the mass of white dwarfs, fuel-exhausted stars, could not exceed 1.44 times that of the Sun, called the Chandrasekhar limit. Chandrasekhar, then 19 years old, further proposed that stars ending their nuclear-burning lifetime above the limit would collapse under their own gravity to become a superdense neutron star or black hole.