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Stellar composition and energy production


The temperature of the sun
Hans Bethe Scientist
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The answer to this puzzle is that there is enormous time in the sun and there also is a very high number of particles, number of protons which can get together and the density of matter near the center of the sun being very high, you get an energy production which is large enough, 2 ergs per gram of sun per second. And because the sun has existed for 4 billion years there's enough time to produce all the energy that the sun has radiated during the interval. So the sun radiates just at the rate that is observed.

To be quite honest when we first did the calculation the sun radiated too much because we had those 40 million degrees, but, well, we put it down anyway. But then Teller persuaded me to come after all to that conference in Washington and at that conference was Strömgren, a Swedish astrophysicist who was most of his life in Denmark, and part of his life in Chicago, who had gone in to Eddington's calculations independently and had come to the conclusion to adopt the suggestion of Russell and Unsöld - namely that hydrogen is the main material in the sun.

[Q] May I interrupt you for just a second. The person who really should be given credit for that is Cecilia Payne, Cecilia Payne... and then it's Russell who picks up on that and popularises it, but it's Cecilia Payne-Gaposchkin who's really the first person to...

Well, I am glad to learn. But it took quite a long time from their suggestion until Eddington himself and Strömgren, I think independently and I believe simultaneously, took up that idea and said 'Okay, the sun is made of hydrogen, and now our temperature goes down from 40 million degrees to 12 million degrees.' Well, that's a little too low, so Strömgren fed in a bit of helium and that got it back up. And at the moment everybody believes it's 15 million degrees, and that's just right so that the Critchfield-Bethe reaction, proton-proton giving deuteron plus positron, gives exactly the right amount of energy.

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: Edward Teller, Bengt Strömgren, Arthur Eddington, Henry Norris Russell, Albrecht Unsöld, Cecilia Payne-Gaposchkin

Duration: 3 minutes, 58 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008