Subrahmanyan Chandrasekhar (/ˌtʃəndrəˈʃeɪkər/;[3] 19 October 1910 – 21 August 1995)[4] was an Indian-American theoretical physicist who made significant contributions to the scientific knowledge about the structure of stars, stellar evolution and black holes.

His mathematical treatment of stellar evolution yielded many of the current theoretical models of the later evolutionary stages of massive stars and black holes.

[8] 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 centre.

In July 1930, Chandrasekhar was awarded a Government of India scholarship to pursue graduate studies at the University of Cambridge, where he was admitted to Trinity College, secured by R. H. Fowler with whom he communicated his first paper.

In his first year at Cambridge, as a research student of Fowler, Chandrasekhar spent his time calculating mean opacities and applying his results to the construction of an improved model for the limiting mass of a degenerate star.

On the advice of Paul Dirac, he spent his final year of graduate studies at the Institute for Theoretical Physics in Copenhagen, where he met Niels Bohr.

After receiving a bronze medal for his work on degenerate stars, Chandrasekhar was awarded his PhD degree at Cambridge in the summer of 1933, with a thesis on rotating self-gravitating polytropes.

He had been so certain of failing to obtain the fellowship that he had already made arrangements to study under Milne that autumn at Oxford, even going to the extent of renting a flat there.

In 1935, Chandrasekhar was invited by the director of the Harvard Observatory, Harlow Shapley, to be a visiting lecturer in theoretical astrophysics for a three-month period.

At the same time, Chandrasekhar met Gerard Kuiper, a noted Dutch astrophysical observationalist who was then a leading authority on white dwarfs.

Having known of Chandrasekhar, Struve was then considering him for one of three faculty posts in astrophysics, along with Kuiper; the other opening had been filled by Bengt Stromgren, a Danish theorist.

[15] After the Laboratory for Astrophysics and Space Research (LASR) was built by NASA in 1966 at the university, Chandrasekhar occupied one of the four corner offices on the second floor.

Chandrasekhar lived at 4800 Lake Shore Drive after the high-rise apartment complex was built in the late 1960s, and later at 5550 Dorchester Building.

After graduating from Cambridge, Chandrasekhar, who was in close contact with Arthur Eddington, presented a full solution to his stellar equation at the Royal Astronomical Society meeting in 1935.

[16] Chandrasekhar sought support from prominent physicists like Léon Rosenfeld, Niels Bohr and Christian Møller who found Eddington's arguments lacking.

"What a scientist tries to do essentially is to select a certain domain, a certain aspect, or a certain detail, and see if that takes its appropriate place in a general scheme which has form and coherence; and, if not, to seek further information which would help him to do that".

[20] Chandrasekhar developed a unique style of mastering several fields of physics and astrophysics; consequently, his working life can be divided into distinct periods.

He would exhaustively study a specific area, publish several papers in it and then write a book summarizing the major concepts in the field.

[8] Chandra worked closely with his students and expressed pride in the fact that over a 50-year period (from roughly 1930 to 1980), the average age of his co-author collaborators had remained the same, at around 30.

[23] During the years 1990 to 1995, Chandrasekhar worked on a project devoted to explaining the detailed geometric arguments in Sir Isaac Newton's Philosophiae Naturalis Principia Mathematica using the language and methods of ordinary calculus.

Many considered him as warm, positive, generous, unassuming, meticulous, and open to debate, while some others as private, intimidating, impatient and stubborn regarding non-scientific matters,[21] and unforgiving to those who ridiculed his work.

"[30] In an interview with Kevin Krisciunas at the University of Chicago, on 6 October 1987, Chandrasekhar commented: "Of course, he (Otto Struve) knew I was an atheist, and he never brought up the subject with me".

[46] Carl Sagan praised him in the book The Demon-Haunted World: "I discovered what true mathematical elegance is from Subrahmanyan Chandrasekhar."

Its research talks were published in 2011 as a book titled Fluid flows to Black Holes: A tribute to S Chandrasekhar on his birth centenary.