As a teen-ager Dr. Chandrasekhar proved a brilliant mathematician, but Sir Arthur Eddington's writing on astrophysics, in addition to a number of unusual observations, turned his attention to astrophysics. One was the discovery in orbit around Sirius, brightest star in the sky, of a tiny white companion. Its orbital behavior indicated that it was extremely dense.
Its message, said Eddington, was, "I am composed of material 3, times denser than anything you have come across; a ton of my material would be a little nugget you could put into a matchbox. New telescopes showed that such "white dwarfs" were common.
By then it had been recognized that atoms were highly compressible but that the gigantic gaseous body of a star was normally supported by radiation from its core. In , Ralph H. Fowler at Cambridge University recognized that once a star's nuclear fuel was exhausted, it would collapse like a punctured balloon, producing a star of great density, a white dwarf. After showing great promise at Presidency College in Madras, Dr.
Chandrasekhar was awarded a Government of India scholarship in to study in England. He set forth by ship, hoping to study under Dr. During the long voyage he studied the implications of relativity theory and the new Fermi-Dirac quantum statistical mechanics for stellar collapse.
Chandrasekhar And His Limit by G. Venkataraman
He calculated what compression-resistant forces within the atom would stop the collapse of a star and form a white dwarf. After several revisions he found that the ability of electrons to resist such compression would be overcome in any star more than 1. On his arrival in England the youthful scientist submitted his proposal to the University of Chicago's Astrophysical Journal. His historic paper was greeted with much skepticism, but was published in In , however, he suffered a humiliating setback when he was invited to present his theory to the Royal Astronomical Society.
Present was Eddington, his hero and a towering figure in British science, who without warning ridiculed the Chandrasekhar paper: "The star has to go on radiating and radiating and contracting and contracting until, I suppose, it gets to a few kilometers' radius, when gravity becomes strong enough to hold the radiation and the star can at last have peace.
This, he said, was a "reductio ad absurdum" of relativity theory.
- Caller Number Three!
- Navigation menu.
- Setting new limits to scientific knowledge.
- Chandrasekhar and His Limit on Apple Books;
There must be a law of nature "to prevent a star from behaving in this absurd way! The episode, Dr. Chandrasekhar said later, "forced me to carefully consider my reasons for wanting to continue to do astrophysics in the face of such a painful experience. In and Dr. Chandrasekhar studied in Germany and Denmark, and in he obtained a doctorate from Cambridge University.
Then, on his return to India in , he married a fellow physicist, Lalitha, who survives him.
In he became a United States citizen, enraging his father, who felt he had betrayed his birthplace, but he remained loyal to his Indian ways, his vegetarianism and deep concern for India's future. He became one of the University of Chicago's most prestigious professors, held in awe and some trepidation by his students. He was Morton D. Hull Distinguished Service Professor from to , when he gained emeritus status.
He was unusually faithful to his academic obligations. John T. A series of papers published between and had its beginning on a trip from India to England in , where the Indian physicist Subrahmanyan Chandrasekhar worked on the calculation of the statistics of a degenerate Fermi gas. Chandrasekhar's work on the limit aroused controversy, owing to the opposition of the British astrophysicist Arthur Eddington.
Eddington was aware that the existence of black holes was theoretically possible, and also realized that the existence of the limit made their formation possible. However, he was unwilling to accept that this could happen. After a talk by Chandrasekhar on the limit in , he replied:.
ISBN 13: 9788173710353
The star has to go on radiating and radiating and contracting and contracting until, I suppose, it gets down to a few km radius, when gravity becomes strong enough to hold in the radiation, and the star can at last find peace. Miller 's biography of Chandrasekhar. Chandra's discovery might well have transformed and accelerated developments in both physics and astrophysics in the s. Instead, Eddington's heavy-handed intervention lent weighty support to the conservative community astrophysicists, who steadfastly refused even to consider the idea that stars might collapse to nothing. As a result, Chandra's work was almost forgotten.
The core of a star is kept from collapsing by the heat generated by the fusion of nuclei of lighter elements into heavier ones. At various stages of stellar evolution , the nuclei required for this process are exhausted, and the core collapses, causing it to become denser and hotter. A critical situation arises when iron accumulates in the core, since iron nuclei are incapable of generating further energy through fusion.
If the core becomes sufficiently dense, electron degeneracy pressure will play a significant part in stabilizing it against gravitational collapse. If a main-sequence star is not too massive less than approximately 8 solar masses , it eventually sheds enough mass to form a white dwarf having mass below the Chandrasekhar limit, which consists of the former core of the star. For more-massive stars, electron degeneracy pressure does not keep the iron core from collapsing to very great density, leading to formation of a neutron star , black hole , or, speculatively, a quark star.
For very massive, low- metallicity stars, it is also possible that instabilities destroy the star completely. Most of this energy is carried away by the emitted neutrinos. Type Ia supernovae derive their energy from runaway fusion of the nuclei in the interior of a white dwarf. This fate may befall carbon — oxygen white dwarfs that accrete matter from a companion giant star , leading to a steadily increasing mass. As the white dwarf's mass approaches the Chandrasekhar limit, its central density increases, and, as a result of compressional heating, its temperature also increases.
This eventually ignites nuclear fusion reactions, leading to an immediate carbon detonation , which disrupts the star and causes the supernova.
This seems to indicate that all type Ia supernovae convert approximately the same amount of mass to energy. According to a group of astronomers at the University of Toronto and elsewhere, the observations of this supernova are best explained by assuming that it arose from a white dwarf that grew to twice the mass of the Sun before exploding. Branch, may have been spinning so fast that a centrifugal tendency allowed it to exceed the limit. Alternatively, the supernova may have resulted from the merger of two white dwarfs, so that the limit was only violated momentarily.
Nevertheless, they point out that this observation poses a challenge to the use of type Ia supernovae as standard candles. Since the observation of the Champagne Supernova in , more very bright type Ia supernovae have been observed that are thought to have originated from white dwarfs whose masses exceeded the Chandrasekhar limit. However, spectropolarimetric observations of SN dc showed it had a polarization smaller than 0.
After a supernova explosion, a neutron star may be left behind. These objects are even more compact than white dwarfs and are also supported, in part, by degeneracy pressure. A neutron star, however, is so massive and compressed that electrons and protons have combined to form neutrons, and the star is thus supported by neutron degeneracy pressure as well as short-range repulsive neutron-neutron interactions mediated by the strong force instead of electron degeneracy pressure. The limiting value for neutron star mass, analogous to the Chandrasekhar limit, is known as the Tolman—Oppenheimer—Volkoff limit.
From Wikipedia, the free encyclopedia.
Maximum mass of a stable white dwarf star. Main article: Champagne Supernova. Three Hundred Years of Gravitation 1st pbk. Cambridge: Cambridge University Press. In Bethe, Hans A. Bibcode : febh. Science PDF. Bibcode : Sci Chandrasekhar limit: The maximum mass of a white dwarf star, about 1. Above this mass, the gravitational pull becomes too great, and the star must collapse to a neutron star or black hole Philosophical Magazine. Astrophysical Journal.
Bibcode : ApJ Monthly Notices of the Royal Astronomical Society.
Bibcode : ZPhy Bibcode : PhyU The Observatory.