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Edwin Salpeter's work in astrophysics


Robert Marshak's work on white dwarfs
Hans Bethe Scientist
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Marshak came here as a graduate student, I think it must have been early in '38, I'm not entirely sure.

[Q] Fall of '37 probably.

And I gave him as a problem to think about the white dwarfs. The white dwarfs are peculiar stars; they have the mass about of the sun, they have much less luminosity and they have very small size, hence their name. And... so how... how can it be that the star of the mass of the sun can have such small size? Where is Eddington? And where is the energy production? Well Marshak very soon showed that if a star of such small size had the mass of the sun, then the temperature would get up to 10, 20 million degrees very near the surface, and so you would get energy production in hydrogen right there and what's left for the interior of the star? Well he concluded then that the white dwarf simply couldn't have any hydrogen, it could only have helium and heavier nuclei and only in that way could you explain that there could be such small size with such a large mass. Marshak's theory which was his thesis is recognized by astrophysicists as the fundamental theory of this... of white dwarfs. There is an astrophysicist at Cal Tech by the name of Greenstein who has worked on white dwarfs all his life and who says right from the beginning we would... be nowhere if it were not for Marshak's thesis. So after that thesis it was accepted that indeed they have no hydrogen, they have helium and heavier nuclei and most of them have helium only near the surface and in the interior they have only carbon and oxygen.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Listeners: Sam Schweber

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).

Tags: California Institute of Technology, Cal Tech, Robert Marshak, Jesse L Greenstein

Duration: 3 minutes, 5 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008