Career
In the year 1935, another opportunity to settle with a solid job in India accosted Chandra. He planned to apply, but canceled his plan after hearing that his good friend S. Chowla (another Indian student he met during his first visit to Cambridge) was also a candidate. Chandra, who admired his work and personality, found it unfair to apply to a position that he may not even be able to take on time, with his other commitment to lecture in America. This disappointed his father into thinking Chandra’s chances of coming back to India had diminished greatly. However, Chandra later found that because of his uncle C.V. Raman’s influence, another scientist, Nagendra Nath, was competing against Chowla for the position that Chowla wanted so badly. In face of this event, Chandra wrote to his father, “I am so disgusted with the whole situation that my desire to settle finally in India and be of some service to Indian science seems to dwindle day by day.”
In January 1937, Chandrasekhar was recruited to the University of Chicago faculty as Assistant Professor by Dr. Otto Struve and President Robert Maynard Hutchins. Here he stayed at Williams Bay, Wisconsin, and Chandra set off on his scientific career at the Yerkes Observatory of the University of Chicago. He was to remain at the university for his entire career, becoming Morton D. Hull Distinguished Service Professor of Theoretical Astrophysics in 1952 and became a naturalized citizen of the United States in 1953. He attained emeritus status at the university in 1985.
During World War II, Chandrasekhar worked at the Ballistic Research Laboratories at the Aberdeen Proving Ground in Maryland. While there, he worked on problems of ballistics; for example, two reports from 1943 were titled, On the decay of plane shock waves and The normal reflection of a blast wave.
Chandrasekhar worked continuously in one specific area of astrophysics for a number of years, then moved to another area. Consequently, his working life can be divided into distinct periods. He studied stellar structure, including the theory of white dwarfs, during the years 1929 to 1939, and subsequently focused on stellar dynamics from 1939 to 1943. Next, he concentrated on the theory of radiative transfer and the quantum theory of the negative ion of hydrogen from 1943 to 1950. This was followed by sustained work on hydrodynamic and hydromagnetic stability from 1950 to 1961. In the 1960s, he studied the equilibrium and the stability of ellipsoidal figures of equilibrium, but also general relativity. During the period, 1971 to 1983 he studied the mathematical theory of black holes, and, finally, during the late 1980s, he worked on the theory of colliding gravitational waves.
During the years 1990 to 1995, Chandrasekhar worked on a project which was devoted to explaining the detailed geometric arguments in Sir Isaac Newton’s Philosophiae Naturalis Principia Mathematica using the language and methods of ordinary calculus. The effort resulted in the book Newton’s Principia for the Common Reader, published in 1995.
Chandrasekhar died of heart failure in Chicago in 1995, and was survived by his wife, Lalitha Chandrasekhar. In the Biographical Memoirs of the 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.»
Legacy
Chandrasekhar’s most famous success was the astrophysical Chandrasekhar limit. The limit describes the maximum mass (~1.44 solar masses) of a white dwarf star, or equivalently, the minimum mass for which a star will ultimately collapse into a neutron star or black hole (following a supernova). The limit was first calculated by Chandrasekhar while on a ship from India to Cambridge, England, where he was to study under the eminent astrophysicist, Sir Ralph Howard Fowler. When Chandrasekhar first proposed his ideas, he was opposed by the British physicist Arthur Eddington, and this may have played a part in his decision to move to the University of Chicago in the United States.
Credits
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Honors
Awards
- Fellow of the Royal Society (1944)
- Henry Norris Russell Lectureship (1949)
- Bruce Medal (1952)
- Gold Medal of the Royal Astronomical Society (1953)
- National Medal of Science award by President Lyndon Johnson (1967)
- Henry Draper Medal (1971)
- Nobel Prize in Physics (1983)
- Copley Medal, the highest honor of the Royal Society (1984)
Named after him
In 1999, 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. The Chandra X-ray Observatory was launched and deployed by Space Shuttle Columbia on July 23, 1999.
The Chandrasekhar number, an important dimensionless number of magnetohydrodynamics, is named after him.
The asteroid 1958 Chandra is also named after Chandrasekhar.
Publications by Chandrasekhar
- Books written by Chandrasekhar
- Chandrasekhar, S. 1958. An Introduction to the Study of Stellar Structure. New York: Dover. ISBN 0-486-60413-6
- Chandrasekhar, S. 2005. Principles of Stellar Dynamics. New York: Dover. ISBN 0-486-44273-X
- Chandrasekhar, S. 1960. Radiative Transfer. New York: Dover. ISBN 0-486-60590-6
- Chandrasekhar, S. 1975. Plasma Physics. Chicago: The University of Chicago Press. ISBN 0-226-10084-7
- Chandrasekhar, S. 1981. Hydrodynamic and Hydromagnetic Stability. New York: Dover. ISBN 0-486-64071-X
- Chandrasekhar, S. 1987. Ellipsoidal Figures of Equilibrium. New York: Dover. ISBN 0-486-65258-0
- Chandrasekhar, S. 1998. The Mathematical Theory of Black Holes. New York: Oxford University Press. ISBN 0-19-850370-9
- Chandrasekhar, S. 1990. Truth and Beauty. Aesthetics and Motivations in Science. Chicago: The University of Chicago Press. ISBN 0-226-10087-1
- Chandrasekhar, S. (1995). Newton’s Principia for the Common Reader. Oxford: Clarendon Press. ISBN 0-19-851744-0
Предел Чандрасекара
Белый
карлик не может быть массивнее Солнца более чем в 1,4 раза.
Как
и всё во Вселенной, звезды рождаются, живут и умирают в свой срок (см. Эволюция
звезд). В зависимости от массы звезды, она заканчивает свой жизненный путь или
огненной вспышкой сверхновой или тихим угасанием в виде белого карлика.
Вся
жизнь звезды — суть непрерывная борьба против центростремительных
гравитационных сил. Прямо сейчас, например, в ядре нашего Солнца происходят термоядерные
реакции, в ходе которых высвобождается энергия, поднимающая температуру
вещества, из которого состоит Солнце, до столь высокого уровня, что оно
начинает вести себя как идеальный газ. Согласно закону состояния идеального
газа, рост температуры в неизменном объеме приводит к пропорциональному росту
давления, в результате чего в ядре Солнца постоянно нагнетается давление,
противодействующее силе тяжести и удерживающее внешние слои Солнца от
гравитационного коллапса — стремительного падения к центру звезды.
Наступит
время (ориентировочно через 6,5 миллиардов лет), когда в недрах Солнца иссякнут
запасы горючего для его термоядерной топки, и силы гравитационного притяжения
после 11 миллиардов лет борьбы победят. Солнце начнет стремительно сжиматься, пока
силы гравитации не натолкнутся на следующий (после побежденного термоядерного)
рубеж обороны, который снова даст силам сжатия достойный отпор давлением. Для
звезд категории Солнца таким барьером становятся свободные электроны внутри
звезды. Электроны подчиняются принципу запрета Паули, согласно которому ни на
одной орбите не могут находиться два электрона в одинаковом состоянии. Это
положение подразумевает, что любому электрону необходимо «жизненное
пространство», и сближаться они могут лишь до определенного предела.
При
гравитационном коллапсе звезды с массой, близкой к солнечной, она сжимается до
размеров порядка размеров Земли, после чего коллапс прекращается в силу
противодействия электронов, которым «некуда» сближаться дальше. Генерировать
энергию звезда на этой стадии уже не может (нет топлива), однако светиться,
остывая, она продолжает еще достаточно долго. Такие звезды и получили название
белых карликов, и среди видимых звезд в ночном небе их немало. По сути, белый
карлик удерживается от полного коллапса равновесием двух сил — гравитационного
притяжения и своего рода давления электронов изнутри. В астрофизике последнее
принято называть давлением вырожденного электронного газа. (Более массивные
звезды продолжают сжиматься, пока не взрываются вспышкой сверхновой — см. Эволюция
звезд.)
В
начале 1930-х годов молодой индийский физик-теоретик Субрахманьян Чандрасекар
(Subrahmanyan Chandrasekhar), работая над теорией белых карликов, сформулировал
важное следствие из запрета Паули, а именно: при превышении массой звезды
определенного предела, равняющегося примерно 1,4 массы Солнца, гравитационные
силы оказываются сильнее сил давления вырожденного газа, и коллапс
продолжается. Именно эта масса M = 1,4Mс и получила название «предел
Чандрасекара»
