Subrahmanyan Chandrasekhar Biography

b:1910 Lahore, India (now Pakistan) d:1995, USA

Subrahmanyan Chandrasekhar wrote two research papers on quantum theory while still an undergraduate at the University of Madras. These were based on papers by Niels Bohr, Erwin Schrödinger and Werner Heisenberg, and (especially) Arnold Somerfeld's paper on Atomic Structure and Spectral Lines. This won him a scholarship to Cambridge in 1930, and on the boat he discovered the Chandrasekhar limit.

Chandrasekhar showed that the upper limit for a  star to become a white dwarf star is 1.4 times the sun's mass. A white dwarf star has a radius of a few thousand kilometres and a density of thousands of kilograms per cubic centimetre. It does not collapse to a black hole because it is supported by repulsion between electrons as predicted by Wolfgang Pauli's exclusion principle. This principle states that two electrons cannot have the same position and velocity. It is based on Heisenberg's uncertainty principle.

Above 1.4 times the Sun's mass, Chandrasekhar concluded, the star will collapse forever to form what is now called a black hole. Although, the term black hole was only introduced by John Wheeler in 1969. Chandrasekhar was not the first to posit the idea of a black hole. In 1783 John Michell suggested that a massive, compact star might have a gravitational field so strong that light could not escape it. 

Chandrasekhar's claim that a star with a mass greater than the Chandrasekhar limit would collapse to form a black hole was ridiculed by Sir Arthur Eddington, one of his heroes at Cambridge. So, in 1936, Chandrasekhar left for the University of Chicago. There he moved into other areas of astronomy, a fruit of which was his classic work An Introduction to Stellar Structure.

In 1953 Chandrasekhar became a US citizen, and the editor of Astrophysical Journal. He remained at the University of Chicago for the rest of his working life. He returned to black hole theory in the 1970s, and won the Nobel Prize in 1983 for his work on white dwarfs and black holes. 

Subrahmanyan Chandrasekhar timeline:

• Arthur Eddington
• Subrahmanyan Chandrasekhar
• Stephen Hawking