Subrahmanyan Chandrasekhar (/ˌtʃəndrəˈʃeɪkər/CHƏN-drə-SHAY-kər;[4]Tamil:சுப்பிரமணியன் சந்திரசேகர்,romanized: Cuppiramaṇiyaṉ Cantiracēkar; 19 October 1910 – 21 August 1995)[5] was anIndian-Americantheoretical physicist who made significant contributions to the scientific knowledge about the structure of stars,stellar evolution andblack holes. He also devoted some of his prime years to fluid dynamics, especially stability and turbulence, and made important contributions. He was awarded the 1983Nobel Prize in Physics along withWilliam A. Fowler for theoretical studies of the physical processes of importance to the structure and evolution of the stars. His mathematical treatment of stellar evolution yielded many of the current theoretical models of the later evolutionary stages of massive stars and black holes.[6][7] Many concepts, institutions and inventions, including theChandrasekhar limit and theChandra X-Ray Observatory, are named after him.[8]
Born in the lateBritish Raj, Chandrasekhar worked on a wide variety of problems in physics during his lifetime, contributing to the contemporary understanding ofstellar structure,white dwarfs,stellar dynamics,stochastic process,radiative transfer, thequantum theory of thehydrogen anion,hydrodynamic andhydromagnetic stability,turbulence, equilibrium and the stability ofellipsoidal figures of equilibrium,general relativity, mathematical theory of black holes and theory of collidinggravitational waves.[9] At theUniversity 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 theirdegenerate matter. He showed that the mass of a white dwarf could not exceed 1.44 times that of the Sun – theChandrasekhar limit. Chandrasekhar revised the models of stellar dynamics first outlined byJan Oort and others by considering the effects of fluctuating gravitational fields within theMilky Way on stars rotating about the galactic centre. His solution to this complex dynamical problem involved a set of twentypartial differential equations, describing a new quantity he termed "dynamical friction", which has the dual effects of decelerating the star and helping to stabilize clusters of stars. Chandrasekhar extended this analysis to the interstellar medium, showing that clouds of galactic gas and dust are distributed very unevenly.
Chandrasekhar was born inLahore on 19 October 1910 of theBritish Raj (present-day atPakistan) into aTamil family,[11] to Sita Balakrishnan (1891–1931) and Chandrasekhara Subrahmanya Ayyar (1885–1960)[12] who was stationed in Lahore as Deputy Auditor General of theNorthwestern Railways at the time of Chandrasekhar's birth. Chandra, as Chandrasekhar was known, had two elder sisters, Rajalakshmi and Balaparvathi, three younger brothers, Vishwanathan, Balakrishnan, and Ramanathan, and four younger sisters, Sarada, Vidya, Savitri, and Sundari. His paternal uncle was the Indian physicist and Nobel laureateChandrasekhara Venkata Raman. His mother was devoted to intellectual pursuits, had translatedHenrik Ibsen'sA Doll's House intoTamil and is credited with arousing Chandra's intellectual curiosity at an early age.[13] The family moved from Lahore toAllahabad in 1916, and finally settled inMadras in 1918.
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-gravitatingpolytropes. On 9 October, he was elected to a Prize Fellowship at Trinity College for the period 1933–1937, becoming only the second Indian to receive a Trinity Fellowship afterSrinivasa Ramanujan 16 years earlier. 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.[14]
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. He travelled to the United States in December. During his visit to Harvard, Chandrasekhar greatly impressed Shapley, but declined his offer of a Harvard research fellowship. At the same time, Chandrasekhar metGerard Kuiper, a noted Dutch astrophysical observationalist who was then a leading authority on white dwarfs. Kuiper had recently been recruited byOtto Struve, the director of theYerkes Observatory inWilliams Bay, Wisconsin, which was run by theUniversity of Chicago, and the university's president,Robert Maynard Hutchins. 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 byBengt Stromgren, a Danish theorist.[14] Following a recommendation from Kuiper, Struve invited Chandrasekhar to Yerkes in March 1936 and offered him the job. Though Chandrasekhar was keenly interested, he initially declined the offer and left for England; after Hutchins sent a radiogram to Chandrasekhar during the voyage, he finally accepted, returning to Yerkes as an assistant professor of Theoretical Astrophysics in December 1936.[14] Hutchins also intervened on an occasion where Chandra's participation on teaching a course organised by Struve, was vetoed by the deanHenry Gale based on a racial prejudice; Hutchins said "By all means have Mr. Chandrasekhar teach".[15]
Chandrasekhar remained at the University of Chicago for his entire career. He was promoted to associate professor in 1941 and to full professor two years later at the age of 33.[14] In 1946, whenPrinceton University offered Chandrasekhar a position vacated byHenry Norris Russell with a salary double that of Chicago's, Hutchins incremented his salary matching with that of Princeton's and persuaded Chandrasekhar to stay in Chicago. In 1952, he became theMorton D. Hull Distinguished Service Professor of Theoretical Astrophysics andEnrico Fermi Institute, uponEnrico Fermi's invitation. In 1953, he and his wife, Lalitha Chandrasekhar, took American citizenship.[16]
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. (The other corners housedJohn A. Simpson,Peter Meyer, andEugene N. Parker.) 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 theRoyal Astronomical Society meeting in 1935. Eddington booked a talk right after Chandrasekhar, where he openly criticized Chandrasekhar's theory. This depressed Chandrasekhar and sparked a scientific dispute. Eddington refused to accept a limit for the mass of a star and proposed an alternative model.[17]
Chandrasekhar sought support from prominent physicists likeLéon Rosenfeld,Niels Bohr andChristian Møller who found Eddington's arguments lacking. The tension persisted through 1930s, as Eddington continued to openly criticize Chandrasekhar during meetings and the two compared each other's theories in publications. Chandrasekhar ultimately completed his theory of white dwarfs in 1939, receiving praise from others in the field. Eddington died in 1944, and despite their disagreements, Chandrasekhar continued to state that he admired Eddington and considered him a friend.[17]
He wrote that his scientific research was motivated by his desire to participate in the progress of different subjects in science to the best of his ability, and that the prime motive underlying his work wassystematization. "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".[21]
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. He would then move on to another field for the next decade and repeat the pattern. Thus he studiedstellar structure, including the theory ofwhite dwarfs, during the years 1929 to 1939, and subsequently focused onstellar dynamics, theory ofBrownian motion from 1939 to 1943. Next, he concentrated on the theory ofradiative transfer and the quantum theory of thenegative ion of hydrogen from 1943 to 1950. This was followed by sustained work onturbulence and hydrodynamic and hydromagnetic stability from 1950 to 1961. In the 1960s, he studied both the equilibrium and the stability of ellipsoidal figures of equilibrium, and general relativity. During the period, 1971 to 1983 he studied the mathematical theory ofblack holes, and, finally, during the late 80s, he worked on the theory of collidinggravitational waves.[9]
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. He insisted that students address him as "Prof. Chandrasekhar" until they received their PhD degree, after which time they (as other colleagues) were encouraged to address him as "Chandra". When Chandrasekhar was working at the Yerkes Observatory in 1940s, he would drive 150 miles (240 km) to and from every weekend to teach a course at the University of Chicago. Two of the students who took the course,Tsung-Dao Lee andChen-Ning Yang, won the Nobel prize before he could get one for himself. Regarding classroom interactions during his lectures, noted astrophysicistCarl Sagan stated from firsthand experience that "frivolous questions" from unprepared students were "dealt with in the manner of a summary execution", while questions of merit "were given serious attention and response".[22]
From 1952 to 1971 Chandrasekhar was editor ofThe Astrophysical Journal.[23] WhenEugene Parker submitted a paper on his discovery ofsolar wind in 1957, two eminent reviewers rejected the paper. However, since Chandra as an editor could not find any mathematical flaws in Parker's work, he went ahead and published the paper in 1958.[24]
During the years 1990 to 1995, Chandrasekhar worked on a project devoted to explaining the detailed geometric arguments in SirIsaac Newton'sPhilosophiae Naturalis Principia Mathematica using the language and methods of ordinary calculus. The effort resulted in the bookNewton's Principia for the Common Reader, published in 1995.
Chandrasekhar also worked on collision of gravitational waves,[25] and algebraically special perturbations.[26]
S. Chandrasekhar with his brothers and sisters in Madras [Chennai], India. From left to right seated are: Bala, Savitri, Chandra, Sarada, Rajam; standing: Vidya, Balakrishnan, Vishwam, Ramanathan, Sundari.
Chandrasekhar was the nephew ofC. V. Raman, who was awarded the Nobel Prize for Physics in 1930.
Chandrasekhar married Lalitha Doraiswamy in September 1936. He met her as a fellow student atPresidency College. He became anaturalised citizen of the U.S. in 1953. 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,[22] and unforgiving to those who ridiculed his work.[27] Chandrasekhar was avegetarian.[28]
Chandrasekhar died of aheart attack at the University of Chicago Hospital in 1995, having survived a prior heart attack in 1975.[22] He was survived by his wife, who died on 2 September 2013 at the age of 102.[29] She was a serious student of literature and western classical music.[27]
Once when involved in a discussion about theBhagavad Gita, Chandrasekhar said: "I should like to preface my remarks with a personal statement in order that my later remarks will not be misunderstood. I consider myself an atheist".[30] This was also confirmed many times in his other talks. Kameshwar C. Wali quoted him saying: "I am not religious in any sense; in fact, I consider myself an atheist."[31] 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".[32] In deference to Subrahmanyan Chandrasekhar's atheistic views, his wife refrained from displaying the small religious icons of deities she had brought with her.[33]
Chandrasekhar was awarded half of theNobel Prize in Physics in 1983 for his studies on the physical processes important to thestructure andevolution of stars. Chandrasekhar accepted this honour, but was upset the citation mentioned only his earliest work, seeing it as a denigration of a lifetime's achievement. He shared it withWilliam A. Fowler.
Chandrasekhar's most notable work is on theastrophysicalChandrasekhar limit. The limit gives the maximum mass of awhite dwarf star, ~1.44solar masses, or equivalently, the minimum mass that must be exceeded for a star to collapse into aneutron star orblack hole (following asupernova). The limit was first calculated by Chandrasekhar in 1930 during his maiden voyage from India toCambridge, England for his graduate studies. In 1979,NASA named the third of its four "Great Observatories" after Chandrasekhar. This followed a naming contest which attracted 6,000 entries from fifty states and sixty-one countries. TheChandra X-ray Observatory was launched and deployed bySpace ShuttleColumbia on 23 July 1999. TheChandrasekhar number, an importantdimensionless number ofmagnetohydrodynamics, is named after him. Theasteroid1958 Chandra is also named after Chandrasekhar. TheHimalayan Chandra Telescope is named after him. In theBiographical Memoirs of Fellows of the Royal Society of London, R. J. Tayler wrote: "Chandrasekhar was a classical applied mathematician whose research was primarily applied in astronomy and whose like will probably never be seen again."[1]
Chandrasekhar supervised 45 PhD students.[44] After his death, his wife Lalitha Chandrasekhar made a gift of his Nobel Prize money to theUniversity of Chicago towards the establishment of the Subrahmanyan Chandrasekhar Memorial Fellowship. First awarded in the year 2000, this fellowship is given annually to an outstanding applicant to graduate school in the PhD programs of the department of physics or the department of astronomy and astrophysics.[45] S. Chandrasekhar Prize of Plasma Physics is an award given by Association of Asia Pacific Physical Societies (AAPS) to outstanding plasma physicists, started in the year 2014.[46]
The Chandra Astrophysics Institute (CAI) is a program offered for high school students who are interested in astrophysics mentored byMIT scientists[47] and sponsored by theChandra X-ray Observatory.[48] Carl Sagan praised him in the bookThe Demon-Haunted World: "I discovered what true mathematical elegance is from Subrahmanyan Chandrasekhar." On 19 October 2017, Google showed aGoogle Doodle in 28 countries honouring Chandrasekhar's 107th birthday and theChandrasekhar limit.[49][50]
Chandrasekhar, S. (1975) [1960].Plasma Physics. Chicago: The University of Chicago Press.ISBN978-0-226-10084-5.
Chandrasekhar, S. (1981) [1961].Hydrodynamic and Hydromagnetic Stability. New York: Dover.ISBN978-0-486-64071-6.
Chandrasekhar, S. (1987) [1969].Ellipsoidal Figures of Equilibrium. New York: Dover.ISBN978-0-486-65258-0.
Chandrasekhar, S. (1998) [1983].The Mathematical Theory of Black Holes. New York: Oxford University Press.ISBN978-0-19-850370-5.
Chandrasekhar, S. (1983) [1983].Eddington: The Most Distinguished Astrophysicist of His Time. Cambridge University Press.ISBN9780521257466.
Chandrasekhar, S. (1990) [1987].Truth and Beauty. Aesthetics and Motivations in Science. Chicago: The University of Chicago Press.ISBN978-0-226-10087-6.
Chandrasekhar, S. (1995).Newton's Principia for the Common Reader. Oxford: Clarendon Press.ISBN978-0-19-851744-3.
Spiegel, E.A. (2011) [1954].The Theory of Turbulence : Subrahmanyan Chandrasekhar's 1954 Lectures. Netherlands: Springer.ISBN978-94-007-0117-5.
Chandrasekhar, S. (1947). Heywood, Robert B. (ed.).The Works of the Mind:The Scientist. Chicago: University of Chicago Press. pp. 159–179.OCLC752682744.
Chandrasekhar, S. (1995).Reminiscences and discoveries on Ramanujan's bust. Royal Society.ASINB001B12NJ8.
Chandrasekhar, S. (1990).How one may explore the physical content of the general theory of relativity. American Mathematical Society.ASINB001B10QTM.
Chandrasekhar published around 380 papers[55][1] in his lifetime. He wrote his first paper in 1928 when he was still an undergraduate student aboutCompton effect[56] and last paper which was accepted for publication just two months before his death was in 1995 which was about non-radial oscillation of stars.[57] TheUniversity of Chicago Press published selected papers of Chandrasekhar in seven volumes.
Chandrasekhar, S. (1989).Selected Papers, Vol 2, Radiative transfer and negative ion of hydrogen. Chicago: University of Chicago Press.ISBN9780226100920.
Chandrasekhar, S. (1990).Selected Papers, Vol 5, Relativistic Astrophysics. Chicago: University of Chicago Press.ISBN9780226100982.
Chandrasekhar, S. (1991).Selected Papers, Vol 6, The Mathematical Theory of Black Holes and of Colliding Plane Waves. Chicago: University of Chicago Press.ISBN9780226101019.
Chandrasekhar, S. (1997).Selected Papers, Vol 7, The non-radial oscillations of star in General Relativity and other writings. Chicago: University of Chicago Press.ISBN9780226101040.
^Osterbrock, Donald E. (December 1998). "Subrahmanyan Chandrasekhar (19 October 1910 – 21 August 1995)".Proceedings of the American Philosophical Society.142 (4). American Philosophical Society:658–665.ISSN0003-049X.JSTOR3152289.(Registration or subscription required)
^abcO'Connor, J. J.; Robertson, E. F."Subrahmanyan Chandrasekhar".Biographies. School of Mathematics and Statistics University of St Andrews, Scotland. Retrieved21 May 2012.
^Chandrasekhar, S. (1943). On the conditions for the existence of three shock waves (Report). Ballistic Research Laboratory, Aberdeen Proving Ground. 367.
^Chandrasekhar, S. (1943). On the Determination of the Velocity of a Projectile from the Beat Waves Produced by Interference with the Waves of Modified Frequency Reflected from the Projectile (Report). Ballistic Research Laboratory, Aberdeen Proving Ground. 365.
^Chandrasekhar, S.; Xanthopoulos, B. C. (1985). "Some exact solutions of gravitational waves coupled with fluid motions".Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.402 (1823):205–224.Bibcode:1985RSPSA.402..205C.doi:10.1098/rspa.1985.0115.S2CID120942390.
Srinivasan, G., ed. (1997).From White Dwarfs to Black Holes: The Legacy of S. Chandrasekhar. Chicago: The University of Chicago Press.ISBN978-0-226-76996-7.
Wali, Kameshwar C., ed. (2001).A Quest For Perspectives. Singapore: World Scientific Publishing Co. Ptd Ltd.ISBN978-1-86094-201-3.
Wali, Kameshwar C., ed. (2020).S Chandrasekhar: Selected Correspondence and Conversations. World Scientific Publishing Co. Ptd Ltd.ISBN978-9811208324.
Wignesan, T., ed. (2004). "The Man who Dwarfed the Stars".The Asianists' Asia.ISSN1298-0358.
Venkataraman, G. (1992).Chandrasekhar and His Limit. Hyderabad, India: Universities Press.ISBN978-81-7371-035-3.
Saikia, D J.; et al., eds. (2011).Fluid flows to Black Holes: A tribute to S Chandrasekhar on his birth centenary. Singapore: World Scientific Publishing Co. Ptd Ltd.ISBN978-981-4299-57-2.
Ramnath, Radhika, ed. (2012).S. Chandrasekhar: Man of Science. Harpercollins.ASINB00C3EWIME.
Alic, Kameshwar C (2011). Kameshwar, C Wali (ed.).A Scientific Autobiography: S Chandrasekhar. A Scientific Autobiography: S Chandrasekhar. Edited by K C Wali. Published by World Scientific Publishing Co. Pte. Ltd.Bibcode:2010sasc.book.....W.doi:10.1142/7686.ISBN978-981-4299-57-2.
Salwi, Dilip, ed. (2004).S. Chandrasekhar: The scholar scientist. Rupa.ISBN978-8129104915.
Pandey, Rakesh Kumar, ed. (2017).Chandrasekhar Limit: Size of White Dwarfs. Lap Lambert Academic Publishing.ISBN978-3330317666.
