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Subrahmanyan Chandrasekhar
RAS obituary
Nobel Laureate 1983
RAS Gold Medalist and George Darwin Lecturer 1953
Fellow 1933 Associate 1970
Fellow of the Royal Society 1944 (Royal Medal 1962 Copley Medal 1984)
Subrahmanyan Chandrasekhar was one of the luminaries of 20th-century astrophysics. While he claimed that he never made a major scientific discovery, history will show his still expanding influence on almost all parts of the subject. This is propagated both through his books, which are models of scientific exposition, and through his former students, many of whom now occupy prominent positions in Science.
Chandra's work is dominated by a fine sense of style. A paper should not merely be relevant and correct; it should also be exact and elegant. It was perhaps this quest for the beautiful that led him to stand back from the hurly-burly of astronomical observations and discoveries and work on the theories that underpin their interpretation. With this stance, he could abstract the essential features of the physical problems and formulate idealized ones whose solutions could satisfy his quest for mathematical style and beauty.
In his editorship of the Astrophysical Journal, he set aside several hours a day and transformed it from a significant journal into the leading publication where work of the highest caliber was to be found. During this time, he read the entire journal and made sure that the articles were strictly refereed, quite commonly by himself. Evidence of what he could do is to be found in Sandage's famous paper announcing the discovery of radio quiet quasars, quasi-stellar galaxies he called them. The date of receipt of the paper is one day after the official date of publication, which Chandra had held back for it.
Chandra was a fine lecturer who held his audience by slowing down whenever he said something intricate. They had to wait for his clear enunciation. His evident enjoyment when they understood added greatly to the sense of charm that pervaded his lectures.
In spite of the heavy demands of editing and lecturing, Chandra kept much of his long day for research, both alone and with collaborators and students. His quiet exterior belied his fiery enthusiasm that inspired all who worked closely with him. His output was prodigious. Early in his scientific career, he established his method. This was to work in one area of astrophysics at a time; to systematize and invent relevant new mathematical techniques; to apply them to every problem in sight that could be elegantly solved, and finally to write a book giving the entire history and development of that subject. While this would include his own work, it would also lay out the foundations so clearly that those who came after could readily reach a high camp before attempting their own climbs to new research summits.
Chandra's work first came to prominence in a famous controversy with Eddington. Eddington had long pondered the problem of how stars can cool down. He knew that when deprived of nuclear sources, their cores would contract and get hotter. Then R.H. Fowler showed that when the densities were high enough, stellar cores would become degenerate with the pressure no longer supplied by heat but by the momentum implied by Heisenberg's relationship, just as electrons are kept out of atomic nuclei. As a student at Presidency College, Madras (1926-29), Chandra read Fowler's paper and published one of his own with Fowler's encouragement. He was granted a scholarship to study under Fowler in Cambridge (1930-33). On the boat journey he realized that electron degeneracy would, at high density, force the electrons to relativistic speeds. Generalizing Fowler's work he derived the pressure-density relationship for a relativistic degenerate electron gas. Later he found that this Stoner-Anderson formula was already known but Chandra realized that for cold stars both non-relativistic and very relativistic cases gave polytropes. He already knew these from the theory of stellar structure. Thus Chandrasekhar gave the first exact determination of the maximum mass of a star that can support itself against its own gravity without the help of heat. Anderson's first determination had been flawed by a poor approximation, whereas Stoner's, which was derived for stars of uniform density, differed from the true Chandrasekhar limit by 10 percent. Eddington, who had thought that Fowler had solved his problem, now saw Chandra's work destroying Fowler's solution for all the massive stars, just where it mattered. Knowing Chandra's mathematics was right, he wrongly attacked the underlying physics in the vain hope of restoring Fowler's original result.
From 1933 to 1937, Chandra held a research fellowship at Trinity, where Eddington was also a fellow. In 1936, he returned briefly to India and married his former classmate Lalitha, who survived him. They delightfully entertained and made welcome to their new home at the Yerkes Observatory, generations of visiting astronomers. His work at the Yerkes Observatory of the University of Chicago culminated in his tenure as the Morton D. Hull Distinguished Service Professor from 1952 until his nominal retirement in 1986.
Chandra's work on stellar structure extended far beyond white dwarfs. The Schönberg-Chandrasekhar limiting mass for a stellar core showed that only 10 percent of the hydrogen in a star will be burned on the main sequence before it evolves to the red over the Hertsprung gap. This work was vital to early age estimates based on stellar evolution.
After writing his book on Stellar Structure, Chandra turned to stellar dynamics, where he made one of his finest discoveries: 'dynamical friction.' This gave rise to a very influential review paper written for and read by a wide range of scientists, 'Noise and Stochastic Processes in Physics and Astronomy.' It was so popular that it was later published as a Dover paperback, as were most of his books. There followed periods of work on radiative transfer, plasma physics, hydrodynamic and hydromagnetic stability, and his discovery of the tensor virial theorem. I think his beautiful work on ellipsoidal configurations of equilibrium began with his desire to find a fruitful area in which to exploit that theorem. The elegance of the subject and his fruitful collaborations with his sometime student Norman Lebovitz diverted his attention from general relativity, which he had already chosen for his next study. His systematic exposition was one of the first to clearly demonstrate the order of post-Newtonian approximation at which gravitational waves occur With his book on Ellipsoidal Configurations written he was at last free for a major attack on fully relativist problems. He chose a systematic study of the Kerr metric and the separability of wave equations in that geometry. These problems were well suited to his remarkable algebraic abilities and stretched him beyond anything he had done previously. One can wonder at these labours when reading his last great research monograph, The Mathematical Theory of Black Holes.
An invitation to speak at the 300th anniversary of Principia led him to read Newton. As he read more, his sense of wonder and his admiration for Newton grew. Expecting to find that modern algebraic methods made it all much easier, he was instead amazed at the insight generated by Newton's geometrical methods. Chandra's last book was written for us, the scientific community, so that we may share his sense of wonder at Newton's almost magical geometric insight and recover something that has been lost down the centuries. It is not written to put Newton in his current historical context. It is not written for historians; it is written so that we can more readily access Newton's work and use his methods. Above all, it is written so that we can teach Newton's insights to a younger generation rather than leave them unread as part of history.
D. Lynden-Bell
Chandra's work is dominated by a fine sense of style. A paper should not merely be relevant and correct; it should also be exact and elegant. It was perhaps this quest for the beautiful that led him to stand back from the hurly-burly of astronomical observations and discoveries and work on the theories that underpin their interpretation. With this stance, he could abstract the essential features of the physical problems and formulate idealized ones whose solutions could satisfy his quest for mathematical style and beauty.
In his editorship of the Astrophysical Journal, he set aside several hours a day and transformed it from a significant journal into the leading publication where work of the highest caliber was to be found. During this time, he read the entire journal and made sure that the articles were strictly refereed, quite commonly by himself. Evidence of what he could do is to be found in Sandage's famous paper announcing the discovery of radio quiet quasars, quasi-stellar galaxies he called them. The date of receipt of the paper is one day after the official date of publication, which Chandra had held back for it.
Chandra was a fine lecturer who held his audience by slowing down whenever he said something intricate. They had to wait for his clear enunciation. His evident enjoyment when they understood added greatly to the sense of charm that pervaded his lectures.
In spite of the heavy demands of editing and lecturing, Chandra kept much of his long day for research, both alone and with collaborators and students. His quiet exterior belied his fiery enthusiasm that inspired all who worked closely with him. His output was prodigious. Early in his scientific career, he established his method. This was to work in one area of astrophysics at a time; to systematize and invent relevant new mathematical techniques; to apply them to every problem in sight that could be elegantly solved, and finally to write a book giving the entire history and development of that subject. While this would include his own work, it would also lay out the foundations so clearly that those who came after could readily reach a high camp before attempting their own climbs to new research summits.
Chandra's work first came to prominence in a famous controversy with Eddington. Eddington had long pondered the problem of how stars can cool down. He knew that when deprived of nuclear sources, their cores would contract and get hotter. Then R.H. Fowler showed that when the densities were high enough, stellar cores would become degenerate with the pressure no longer supplied by heat but by the momentum implied by Heisenberg's relationship, just as electrons are kept out of atomic nuclei. As a student at Presidency College, Madras (1926-29), Chandra read Fowler's paper and published one of his own with Fowler's encouragement. He was granted a scholarship to study under Fowler in Cambridge (1930-33). On the boat journey he realized that electron degeneracy would, at high density, force the electrons to relativistic speeds. Generalizing Fowler's work he derived the pressure-density relationship for a relativistic degenerate electron gas. Later he found that this Stoner-Anderson formula was already known but Chandra realized that for cold stars both non-relativistic and very relativistic cases gave polytropes. He already knew these from the theory of stellar structure. Thus Chandrasekhar gave the first exact determination of the maximum mass of a star that can support itself against its own gravity without the help of heat. Anderson's first determination had been flawed by a poor approximation, whereas Stoner's, which was derived for stars of uniform density, differed from the true Chandrasekhar limit by 10 percent. Eddington, who had thought that Fowler had solved his problem, now saw Chandra's work destroying Fowler's solution for all the massive stars, just where it mattered. Knowing Chandra's mathematics was right, he wrongly attacked the underlying physics in the vain hope of restoring Fowler's original result.
From 1933 to 1937, Chandra held a research fellowship at Trinity, where Eddington was also a fellow. In 1936, he returned briefly to India and married his former classmate Lalitha, who survived him. They delightfully entertained and made welcome to their new home at the Yerkes Observatory, generations of visiting astronomers. His work at the Yerkes Observatory of the University of Chicago culminated in his tenure as the Morton D. Hull Distinguished Service Professor from 1952 until his nominal retirement in 1986.
Chandra's work on stellar structure extended far beyond white dwarfs. The Schönberg-Chandrasekhar limiting mass for a stellar core showed that only 10 percent of the hydrogen in a star will be burned on the main sequence before it evolves to the red over the Hertsprung gap. This work was vital to early age estimates based on stellar evolution.
After writing his book on Stellar Structure, Chandra turned to stellar dynamics, where he made one of his finest discoveries: 'dynamical friction.' This gave rise to a very influential review paper written for and read by a wide range of scientists, 'Noise and Stochastic Processes in Physics and Astronomy.' It was so popular that it was later published as a Dover paperback, as were most of his books. There followed periods of work on radiative transfer, plasma physics, hydrodynamic and hydromagnetic stability, and his discovery of the tensor virial theorem. I think his beautiful work on ellipsoidal configurations of equilibrium began with his desire to find a fruitful area in which to exploit that theorem. The elegance of the subject and his fruitful collaborations with his sometime student Norman Lebovitz diverted his attention from general relativity, which he had already chosen for his next study. His systematic exposition was one of the first to clearly demonstrate the order of post-Newtonian approximation at which gravitational waves occur With his book on Ellipsoidal Configurations written he was at last free for a major attack on fully relativist problems. He chose a systematic study of the Kerr metric and the separability of wave equations in that geometry. These problems were well suited to his remarkable algebraic abilities and stretched him beyond anything he had done previously. One can wonder at these labours when reading his last great research monograph, The Mathematical Theory of Black Holes.
An invitation to speak at the 300th anniversary of Principia led him to read Newton. As he read more, his sense of wonder and his admiration for Newton grew. Expecting to find that modern algebraic methods made it all much easier, he was instead amazed at the insight generated by Newton's geometrical methods. Chandra's last book was written for us, the scientific community, so that we may share his sense of wonder at Newton's almost magical geometric insight and recover something that has been lost down the centuries. It is not written to put Newton in his current historical context. It is not written for historians; it is written so that we can more readily access Newton's work and use his methods. Above all, it is written so that we can teach Newton's insights to a younger generation rather than leave them unread as part of history.
D. Lynden-Bell
Subrahmanyan Chandrasekhar's obituary appeared in Journal of the Royal Astronomical Society 37:2 (1996), 261-263.