Chandrasekhar, Subrahmanyan (“Chandra”)

(b. 19 October 1910 in Lahore, British India [later Pakistan]; d. 21 August 1995 in Chicago, Illinois), Nobel laureate and one of the foremost scientists of the twentieth century, known for his wide-ranging contributions to physics, astrophysics, and applied mathematics.

Chandrasekhar, known simply as “Chandra” in the scientific world, was one of ten children of Chandrasekhara Subrahmanya Ayyar, an officer in the British government service, and Sitalakkshmi Balakrishnan, a woman of great talent and intellectual attainments who played a pivotal role in Chandrasekhar’s career. Chandrasekhar’s early education took place at home under the tutelage of his parents and private tutors. When he was twelve, his family moved to Madras, where he began his regular schooling at the Hindu High School in Triplicane, which he attended from 1922 to 1925. Chandrasekhar then received his university education at the Presidency College in Madras. He earned a bachelor of science degree with honors in physics in 1930, and was awarded a Government of India scholarship for graduate studies at Cambridge University in England.

Chandrasekhar left India for England in July 1930. At Cambridge he became a research student under the supervision of the pioneering theoretical astrophysicist Ralph Howard Fowler. He spent the third year of his graduate scholarship in Copenhagen, Denmark, at Niels Bohr’s Institute for Theoretical Physics before completing work on his Cambridge Ph.D. in the summer of 1933. In October he was elected a fellow of Trinity College, Cambridge, which he attended from 1933 to 1937. The only Indian previously elected to this prestigious fellowship was the mathematics prodigy Srinivasa Ramanujan, sixteen years before. Chandrasekhar visited the United States for the first time from January to March 1936. His stay at Harvard University in Cambridge, Massachusetts, was at the invitation of the director of the Harvard College Observatory, Dr. Harlow Shapley. In the late summer of 1936, Chandrasekhar returned to his native country for a short visit to marry Lalitha Doraiswamy, whom he had met while both were undergraduates at Presidency College. They wed on 11 September 1936 and did not have children.

In January 1937 Chandrasekhar joined the faculty of the University of Chicago at the Yerkes Observatory in Williams Bay, Wisconsin. Chandrasekhar and his wife lived in Williams Bay for the next twenty-seven years. In 1964 they moved to Chicago, living in the Hyde Park neighborhood near the university. Elected a fellow of the Royal Society of London in 1944 and named the Morton D. Hull Distinguished Service Professor in 1946, Chandrasekhar remained at the University of Chicago until his death. Chandrasekhar and Lalitha became citizens of the United States in 1953.

Chandrasekhar’s scientific career began while an undergraduate at the Presidency College, when he published his first paper, “The Compton Scattering and the New Statistics,” in the Proceedings of the Royal Society in 1929. In 1930, during his voyage from India to England, he made the fundamental discovery that came to be known as the “Chandrasekhar limit,” the upper limit on the mass of a star that could become a white dwarf (that limit being 1.44 times the mass of the sun). Its significance, however, was undermined for a time as the result of an unexpected encounter during the January 1935 meeting of the Royal Astronomical Society in London, between Chandrasekhar and the internationally famous Sir Arthur Stanley Eddington, who dismissed the limit as “Reductio ad absurdum behaviour” of a star. More than twenty years passed before the Chandrasekhar limit became an accepted fact. It was hailed as one of the most important discoveries of the twentieth century, because it paved the way to the discovery of the other two terminal stages of a star: neutron stars and black holes.

Chandrasekhar’s distinctive pattern of research encompassed diverse areas, each of which occupied Chandrasekhar for a period of five to ten years. Each period of study resulted in a series of long papers and ended with a monograph. Speaking about his monographs and his motivation for research, Chandrasekhar, in the autobiographical account published with his Nobel lecture, said:

After the early years, my scientific work has followed a certain pattern motivated, principally, by a quest after perspectives. In practice, this quest consists in my choosing (after some trials and tribulations) a certain area, which appears amenable to cultivation and compatible with my taste, ability, and temperament. And when after some years of study, I feel that I have accumulated a sufficient body of knowledge and achieved a view of my own, I have the urge to present my point of view ab initio [from the beginning], in a coherent account with order, form, and structure.

Chandrasekhar’s major contributions to twentieth-century astrophysics were in the studies of the structures and stability problems during stellar evolution; stellar dynamics dealing with distribution of matter and motion in the aggregation of stars, star clusters, and galaxies; the principles of radiation transfer and radiation equilibrium in stellar atmospheres, particularly the theory of the illumination and the polarization of the sunlit sky; and the theory of the negative ion of hydrogen that resolved a longstanding controversy of the 1930s pertaining to the solar spectrum and the abundance of hydrogen in the sun. Beginning in 1960, Chandrasekhar focused his attention mainly on Albert Einstein’s general relativity and bringing it into its “natural home,” astronomy. In his first paper on relativity in 1964, he made a major discovery in the relativistic theory of stellar pulsations: the relativistic instability against gravitational collapse. He developed the theory to take into account relativistic effects systematically and to establish beyond doubt, at least theoretically, the existence of black holes in the universe. His contributions to the mathematical theory of black holes and his studies of the exact solutions of Einstein’s equations provided new and important physical and mathematical insights into the richness and beauty of Einstein’s theory. During the last decade of his life, Chandrasekhar was devoted to the study of Sir Isaac Newton’s Principia (1687) and in 1995, just before he died of a heart attack, his monumental treatise, Newton’s Principia for the Common Reader, was published. His remains were cremated. Among the numerous prizes, honors, and medals bestowed on Chandrasekhar for his scientific accomplishments were the Nobel Prize in physics (1983) and the Copley Medal of the Royal Society of London (1984). He was elected to the National Academy of Sciences in 1955, and was also the recipient of National Medal of Science awarded by President Lyndon Johnson (1966) and Padma Vibhusana (the highest honor that the Indian government bestows on a noncitizen) by the president of India (1968).

Teaching was an integral part of Chandrasekhar’s research. A superb teacher and lecturer, well known for elegance and scholarship, he made a lasting impression on the students who came from all over the world to do graduate work under his supervision. He was the sole editor of the Journal of Astronomy and Astrophysics for almost twenty years and was chiefly responsible for making it the foremost journal of its kind in the world. Chandrasekhar was a strong advocate of the pursuit of science in all countries and resented any suggestion that developing countries should abandon pure science in favor of what some believed were more practical needs. His life stood for singular dedication to the pursuit of science, and to practicing its precepts and living up to its values to the furthest possible limit in one’s life.

Some two-thirds of Chandrasekhar’s research papers are collected together in his Selected Papers, 7 vols. (1989–1997). The end of the sixth volume contains a complete bibliography of his publications. While his six monographs are technical in nature, his Truth and Beauty: Aesthetics and Motivations in Science (1987) is a collection of seven lectures in which he explores, in a semipopular way, the motivations in the pursuit of science and the patterns of scientific creativity. See also Kameshwar C. Wali, Chandra: A Biography of S. Chandrasekhar (1991), and Kameshwar C. Wali, ed., S. Chandrasekhar: The Man Behind the Legend (1997), a collection of essays by some of his students and close associates. An obituary is in the New York Times (22 Aug. 1995).

Kameshwar C. Wali