Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar (1910-1995) worked on the origins, structure, and dynamics of stars and earned a prominent place in the annals of science. The Nobel Prize-winning physicist's most celebrated work concerns the radiation of energy from stars, particularly the dying fragments known as white dwarf stars.

Subrahmanyan Chandrasekhar was an Indian-born American astrophysicist and applied mathematician whose work on the origins, structure, and dynamics of stars secured him a prominent place in the annals of science. His most celebrated work concerns the radiation of energy from stars, particularly white dwarf stars, which are the dying fragments of stars. Chandrasekhar demonstrated that the radius of a white dwarf star is related to its mass: the greater its mass, the smaller its radius. Chandrasekhar made numerous other contributions to astrophysics. His expansive research and published papers and books include topics such as the system of energy transfer within stars, stellar evolution, stellar structure, and theories of planetary and stellar atmospheres. For nearly twenty years, he served as the editor-in-chief of the Astrophysical Journal, the leading publication of its kind in the world. For his immense contribution to science, Chandrasekhar, who died in 1995, received numerous awards and distinctions, most notably the 1983 Nobel Prize for Physics for his research into the depths of aged stars.

Chandrasekhar, better known as Chandra, was born on October 19, 1910, in Lahore, India (now part of Pakistan), the first son of C. Subrahmanyan Ayyar and Sitalakshmi nee (Divan Bahadur) Balakrishnan. Chandra came from a large family: he had two older sisters, four younger sisters, and three younger brothers. As the firstborn son, Chandra inherited his paternal grandfather's name, Chandrasekhar. His uncle was the Nobel Prize-winning Indian physicist, Sir C. V. Raman.

Chandra received his early education at home, beginning when he was five. From his mother he learned Tamil, from his father, English and arithmetic. He set his sights upon becoming a scientist at an early age, and to this end, undertook at his own initiative some independent study of calculus and physics. The family moved north to Lucknow in Uttar Pradesh when Chandra was six. In 1918, the family moved again, this time south to Madras. Chandrasekhar was taught by private tutors until 1921, when he enrolled in the Hindu High School in Triplicane. With typical drive and motivation, he studied on his own and steamed ahead of the class, completing school by the age of fifteen.

After high school, Chandra attended Presidency College in Madras. For the first two years, he studied physics, chemistry, English, and Sanskrit. For his B.A. honors degree he wished to take pure mathematics but his father insisted that he take physics. Chandra resolved this conflict by registering as an honors physics student but attending mathematics lectures. Recognizing his brilliance, his lecturers went out of their way to accommodate Chandra. Chandra also took part in sporting activities and joined the debating team. A highlight of his college years was the publication of his paper, "The Compton Scattering and the New Statistics." These and other early successes while he was still an eighteen-year-old undergraduate only strengthened Chandra's resolve to pursue a career in scientific research, despite his father's wish that he join the Indian civil service. A meeting the following year with the German physicist Werner Heisenberg, whom Chandra, as the secretary of the student science association, had the honor of showing around Madras, and Chandra's attendance at the Indian Science Congress Association Meeting in early 1930, where his work was hailed, doubled his determination.

Upon graduating with a M.A. in 1930, Chandra set off for Trinity College, Cambridge, as a research student, courtesy of an Indian government scholarship created especially for him (with the stipulation that upon his return to India, he would serve for five years in the Madras government service). At Cambridge, Chandra turned to astrophysics, inspired by a theory of stellar evolution that had occurred to him as he made the long boat journey from India to Cambridge. It would preoccupy him for the next ten years. He also worked on other aspects of astrophysics and published many papers.

In the summer of 1931, he worked with physicist Max Born at the Institut für Theoretische Physik at Göttingen in Germany. There, he studied group theory and quantum mechanics (the mathematical theory that relates matter and radiation) and produced work on the theory of stellar atmospheres. During this period, Chandra was often tempted to leave astrophysics for pure mathematics, his first love, or at least for physics. He was worried, though, that with less than a year to go before his thesis exam, a change might cost him his degree. Other factors influenced his decision to stay with astrophysics, most importantly, the encouragement shown him by astrophysicist Edward Arthur Milne. In August 1932, Chandra left Cambridge to continue his studies in Denmark under physicist Niels Bohr. In Copenhagen, he was able to devote more of his energies to pure physics. A series of Chandra's lectures on astrophysics given at the University of Liège, in Belgium, in February 1933 received a warm reception. Before returning to Cambridge in May 1933 to sit his doctorate exams, he went back to Copenhagen to work on his thesis.

Chandrasekhar's uncertainty about his future was assuaged when he was awarded a fellowship at Trinity College, Cambridge. During a four-week trip to Russia in 1934, where he met physicists Lev Davidovich Landau, B. P. Geraismovic, and Viktor Ambartsumian, he returned to the work that had led him into astrophysics to begin with, white dwarfs. Upon returning to Cambridge, he took up research of white dwarfs again in earnest.

As a member of the Royal Astronomical Society since 1932, Chandra was entitled to present papers at its twice monthly meetings. It was at one of these that Chandra, in 1935, announced the results of the work that would later make his name. As stars evolve, he told the assembled audience, they emit energy generated by their conversion of hydrogen into helium and even heavier elements. As they reach the end of their life, stars have progressively less hydrogen left to convert and emit less energy in the form of radiation. They eventually reach a stage when they are no longer able to generate the pressure needed to sustain their size against their own gravitational pull and they begin to contract. As their density increases during the contraction process, stars build up sufficient internal energy to collapse their atomic structure into a degenerate state. They begin to collapse into themselves. Their electrons become so tightly packed that their normal activity is suppressed and they become white dwarfs, tiny objects of enormous density. The greater the mass of a white dwarf, the smaller its radius, according to Chandrasekhar. However, not all stars end their lives as stable white dwarfs. If the mass of evolving stars increases beyond a certain limit, eventually named the Chandrasekhar limit and calculated as 1.4 times the mass of the sun, evolving stars cannot become stable white dwarfs. A star with a mass above the limit has to either lose mass to become a white dwarf or take an alternative evolutionary path and become a supernova, which releases its excess energy in the form of an explosion. What mass remains after this spectacular event may become a white dwarf but more likely will form a neutron star. The neutron star has even greater density than a white dwarf and an average radius of about .15 km. It has since been independently proven that all white dwarf stars fall within Chandrasekhar's predicted limit, which has been revised to equal 1.2 solar masses.

Unfortunately, although his theory would later be vindicated, Chandra's ideas were unexpectedly undermined and ridiculed by no less a scientific figure than astronomer and physicist Sir Arthur Stanley Eddington, who dismissed as absurd Chandra's notion that stars can evolve into anything other than white dwarfs. Eddington's status and authority in the community of astronomers carried the day, and Chandra, as the junior, was not given the benefit of the doubt. Twenty years passed before his theory gained general acceptance among astrophysicists, although it was quickly recognized as valid by physicists as noteworthy as Wolfgang Pauli, Niels Bohr, Ralph H. Fowler, and Paul Dirac. Rather than continue sparring with Eddington at scientific meeting after meeting, Chandra collected his thoughts on the matter into his first book, An Introduction to the Study of Stellar Structure, and departed the fray to take up new research around stellar dynamics. An unfortunate result of the scientific quarrel, however, was to postpone the discovery of black holes and neutron stars by at least twenty years and Chandra's receipt of a Nobel Prize for his white dwarf work by fifty years. Surprisingly, despite their scientific differences, he retained a close personal relationship with Eddington.

Chandra spent from December 1935 until March 1936 at Harvard University as a visiting lecturer in cosmic physics. While in the United States, he was offered a research associate position at Yerkes Observatory at Williams Bay, Wisconsin, staring in January 1937. Before taking up this post, Chandra returned home to India to marry the woman who had waited for him patiently for six years. He had known Lalitha Doraiswamy, daughter of Captain and Mrs. Savitri Doraiswamy, since they had been students together at Madras University. After graduation, she had undertaken a master's degree. At the time of their marriage, she was a headmistress. Although their marriage of love was unusual, as both came from fairly progressive families and were both of the Brahman caste, neither of their families had any real objections. After a whirlwind courtship and wedding, the young bride and groom set out for the United States. They intended to stay no more than a few years, but, as luck would have it, it became their permanent home.

At the Yerkes Observatory, Chandra was charged with developing a graduate program in astronomy and astrophysics and with teaching some of the courses. His reputation as a teacher soon attracted top students to the observatory's graduate school. He also continued researching stellar evolution, stellar structure, and the transfer of energy within stars. In 1938, he was promoted to assistant professor of astrophysics. During this time Chandra revealed his conclusions regarding the life paths of stars.

During the World War II, Chandra was employed at the Aberdeen Proving Grounds in Maryland, working on ballistic tests, the theory of shock waves, the Mach effect, and transport problems related to neutron diffusion. In 1942, he was promoted to associate professor of astrophysics at the University of Chicago and in 1943, to professor. Around 1944, he switched his research from stellar dynamics to radiative transfer. Of all his research, the latter gave him, he recalled later, more fulfillment. That year, he also achieved a lifelong ambition when he was elected to the Royal Society of London. In 1946, he was elevated to Distinguished Service Professor. In 1952, he became Morton D. Hull Distinguished Service Professor of Astrophysics in the departments of astronomy and physics, as well as at the Institute for Nuclear Physics at the University of Chicago's Yerkes Observatory. Later the same year, he was appointed managing editor of the Astrophysical Journal, a position he held until 1971. He transformed the journal from a private publication of the University of Chicago to the national journal of the American Astronomical Society. The price he paid for his editorial impartiality, however, was isolation from the astrophysical community.

Chandra became a United States citizen in 1953. Despite receiving numerous offers from other universities, in the United States and overseas, Chandra never left the University of Chicago, although, owing to a disagreement with Bengt Strömgren, the head of Yerkes, he stopped teaching astrophysics and astronomy and began lecturing in mathematical physics at the University of Chicago campus. Chandra voluntarily retired from the University of Chicago in 1980, although he remained on as a post-retirement researcher. In 1983, he published a classic work on the mathematical theory of black holes. Afterwards, he studied colliding waves and the Newtonian two-center problem in the framework of the general theory of relativity. His semi-retirement also left him with more time to pursue his hobbies and interests: literature and music, particularly orchestral, chamber, and South Indian.

During his long career, Chandrasekhar received many awards. In 1947, Cambridge University awarded him its Adams Prize. In 1952, he received the Bruce Medal of the Astronomical Society of the Pacific, and the following year, the Gold Medal of the Royal Astronomical Society. In 1955, Chandrasekhar became a Member of the National Academy of Sciences. The Royal Society of London bestowed upon him its Royal Medal seven years later. In 1962, he was also presented with the Srinivasa Ramanujan Medal of the Indian National Science Academy. The National Medal of Science of the United States was conferred upon Chandra in 1966; and the Padma Vibhushan Medal of India in 1968. Chandra received the Henry Draper Medal of the National Academy of Sciences in 1971 and the Smoluchowski Medal of the Polish Physical Society in 1973. The American Physical Society gave him its Dannie Heineman Prize in 1974. The crowning glory of his carer came nine years later when the Royal Swedish Academy awarded Chandrasekhar the Nobel Prize for Physics. ETH of Zurich gave the Indian astrophysicist its Dr. Tomalla Prize in 1984, while the Royal Society of London presented him with its Copley Prize later that year. Chandra also received the R. D. Birla Memorial Award of the Indian Physics Association in 1984. In 1985, the Vainu Bappu Memorial Award of the Indian National Science Academy was conferred upon Chandrasekhar. In May 1993, Chandra received the state of Illinois's highest honor, Lincoln Academy Award, for his outstanding contributions to science.

While his contribution to astrophysics was immense, Chandra always preferred to remain outside the mainstream of research. He died on August 21, 1995, at the age of 82 in Chicago. The respected physicist once described himself to his biographer, Kameshar C. Wali, as "a lonely wanderer in the byways of science." Throughout his life, Chandra strove to acquire knowledge and understanding, according to an autobiographical essay published with his Nobel lecture, motivated "principally by a quest after perspectives."

Further Reading on Subrahmanyan Chandrasekhar

The Biographical Dictionary of Scientists, Astronomers, Blond Educational Company (London), 1984, pp. 36.

Chambers Biographical Encyclopedia of Scientists, Facts-on-File, 1981.

Goldsmith, Donald, The Astronomers, St. Martin's Press, 1991.

Great American Scientists, Prentice-Hall, 1960.

Land, Kenneth R. and Owen Gingerich, editors, A Sourcebook in Astronomy and Astrophysics, Harvard University Press, 1979.

Modern Men of Science, McGraw-Hill, 1966, p. 97.

Wali, Kameshwar C., Chandra: A Biography of S. Chandrasekhar, Chicago University Press, 1991.

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