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Hans Bethe - Robert Marshak's work on white dwarfs (75/158)

1,786 views · Published 27 June 2017 · 3:05 · Indexed 21 October 2026

Channel: Web of Stories - Life Stories of Remarkable People · 2017 · Science & Technology

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German-born theoretical physicist Hans Bethe (1906-2005) was one of the first scientists to join the Manhattan Project, later strongly advocating nuclear disarmament. In 1967, he was awarded the Nobel Prize in Physics for his theory of stellar nucleosynthesis. [Listener: Sam Schweber; date recorded: 1996]

TRANSCRIPT: Marshak came here as a graduate student, I think it must have been early in '38, I'm not entirely sure. 

[SS] 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.

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