OBITUARY: Professor Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar was a towering figure in 20th-century science, an outstanding astrophysicist who shared the 1983 Nobel Prize for physics for his work on white dwarf stars and black holes.

"Chandra" came from the intellectual elite of India. His father had risen high in the Indian Civil Service, and put pressure on his brilliant son to follow the same profession. With the gentle support of his mother, Chandra was able to persist in his choice of a career in pure science; he could point to the example of his father's brother C. V. Raman, who had resigned from the Civil Service after 10 years in order to pursue science, achieving fame and a Nobel Prize for Physics for his discovery of the Raman effect. While still a student, Chandra had already published a paper in the Proceedings of the Royal Society, sponsored by R. H. Fowler of Cambridge. In 1930 he departed for England on a Government of India scholarship, saying goodbye for the last time to his ailing mother.

It was while travelling to England that Chandra made the discovery for which he is probably best known in the general scientific world. Some years earlier, by applying a newly enunciated principle of quantum mechanics, Alfred Fowler had argued that the white dwarf stars - faint collapsed bodies of stellar mass but with planetary radii, and so with densities of about a ton to the cubic inch - would be the natural ultimate state to which all normal stars such as our Sun would evolve, once all nuclear energy sources had been exhausted.

Chandra showed that as a consequence of Einstein's special relativity, this graveyard was available only for stars of mass less than a critical value - "Chandrasekhar's limit". However, this conclusion - now firmly built into modern astrophysics - was resisted violently by Sir Arthur Eddington, Plumian Professor of Astronomy at Cambridge, and one of Chandra's unofficial hosts, who dismissed Chandra's work as "almost a reductio ad absurdum". One can imagine what a traumatic experience it was for the 24-year old expatriate to be savaged by such a figure.

Although the leading theoretical physicists (occasionally in public but more often in private) sided with Chandra in the ongoing controversy, Eddington remained unconvinced. There was indeed the dilemma that Chandra's work had reopened: what would be the fate of stars that ended their lives with masses too great to be able to settle down as either a white dwarf or as a (subsequently studied) neutron star? It is surprising that Eddington, who did so much to champion Einstein's theory of gravitation ("general relativity") did not conclude that a massive dying star could end its days as what is now known as a black hole, discovered by K. Schwarzschild to be a solution of Einstein's equations.

Decades later, Chandra in characteristic style began a systematic study of some areas in general relativity, culminating in his penultimate treatise on the theory of black holes, devoted largely to the properties of R.P. Kerr's remarkable generalisation for a rotating black hole of the Schwarzschild solution. By then, the opposition of the long departed Eddington was part of history, with Chandra in the Eddington centenary lectures paying tribute to "Eddington: the most distinguished astrophysicist of his time".

In 1984, the year after his Nobel Prize, Chandra received the Royal Society's highest award, the Copley Medal. His many other awards included the Bruce Medal of the Astronomical Society of the Pacific, the Henry Draper Medal of the National Academy of Sciences, and the Gold Medal of the Royal Astronomical Society.

In 1936 Chandra returned from Cambridge to the family home at Madras to marry his fiancee Lalitha, whom he had met in their student days.Lalitha was an ever-present support for Chandra in their 59 years together. After a short period in Cambridge they settled in the United States. For most of the time Chandra was on the staff of the University of Chicago, originally at Yerkes Observatory, in Wisconsin, and then at the city campus.

As if it were not enough to produce scientific work of quality and quantity that would have kept three men busy, Chandra undertook also for nearly 20 years the herculean task of editing the Astrophysical Journal. When he began, APJ was essentially a private journal of the University of Chicago. In the words of his biographer K. C. Wali, "Chandra played a decisive role in transforming it into the national journal of the American Astronomical Society." He could only succeed in combining the editorship with his scientific output by becoming in his own words "autocratic, the complete master, and totally responsible for the journal". His draconian style ensured that the journal greatly enhanced its world-wide reputation.

Chandra's style of work was unique, and his output phenomenal. He would move into a new area, master the basic physics and its mathematical formulation, and proceed to make important - often outstanding - contributions to its mathematical development. He felt that too much attention was paid to his early work on white dwarfs, at the expense of his later wide-ranging scholarship. A series of monographs tell the story of his scientific life: "An introduction to the study of stellar structure"; "Principles of stellar dynamics"; "Radiative transfer"; "Hydrodynamic and hydromagnetic stability"; "Ellipsoidal figures of equilibrium", "The mathematical theory of black holes"; and "Newton's Principia for the common reader". There are in addition six published volumes of selected papers, containing material not subsumed into the monographs. His readership was not confined to the astronomical world; for example, the volume on radiative transfer became essential reading for those concerned with neutron diffusion in nuclear reactors.

The study on the equilibrium and stability of rotating self-gravitating ellipsoids goes back to Newton, and had attracted over the centuries the attention of a distinguished series of astronomers and mathematicians. It is gratifying to know that the 20th century produced a Chandra and his collaborator at Chicago Norman Lebovitz, who responded to an inherited challenge with such eclat.

After his heroic efforts in general relativity, which included important work on gravitational radiation, Chandra returned to Newtonian mechanics, as presented in the Principia. By a rearrangement of material, and by supplying modern versions of Newton's proofs, Chandra aimed to "eliminate the impediments of language and of syntax" that prevent "the common reader" from comprehending the enormous intellectual achievement of the Principia.

Only last month, Chandra wrote to a Cambridge colleague that this volume on the Principia, together with an accompanying paper, were really the last things he intended doing in science. His death so soon after the completion of his last treatise seems symbolic. At the end of Wali's biography, Chandra did question the single-minded pursuit of knowledge that had dominated his life; but one could not imagine him ceasing to be creative, just being content to relax with Beethoven and Shakespeare (whom he coupled with Newton in his lecture on "Patterns of creativity").

Leon Mestel

Subrahmanyan Chandrasekhar, applied mathematician, astrophysicist: born Lahore 19 October 1910: Fellow of Trinity College, Cambridge 1933-37, Honorary Fellow 1981; FRS 1944; Morton D. Hull Distinguished Service Professor of Theoretical Astrophysics, University of Chicago 1937-85 (Emeritus); Managing Editor, Astrophysical Journal 1952-71; Nobel Prize for Physics 1983; married 1936 Lalitha Doraiswamy; died Chicago 21 August 1995.