Hydrogen fusion seemed like a good candidate because according to E = m c 2, the small mass difference between the fusing hydrogen and the resulting helium would liberate an enormous amount of energy.

Since the earth could not predate the sun, a much more copious energy source was needed.Ī long series of discoveries beginning with Einstein’s relativity in 1905 led up to Bethe’s discovery of the correct nuclear reactions. The old theory, that the sun’s energy was produced by gravitational contraction, could supply only 30 million years of stellar energy, but biologists and geologists were estimating the earth was much older. Physicists at the turn of the 20th century realized that the existing paradigm for stellar energy production was wrong. He won the 1967 Nobel Prize in physics for this discovery.

In the papers, Bethe outlined two separate sets of nuclear fusion reactions that power stars and predicted how one or the other would dominate depending on the temperature of a given star. The source of stellar energy was an intense area of research in the early 20th century, and Hans Bethe of Cornell University solved the last major piece of the problem with a pair of papers in 1939 in the Physical Review. Focus Landmarks feature important papers from the archive. ×ĪPS has put the entire Physical Review archive online, back to 1893. Hans Bethe’s papers explained the precise nuclear reactions that are the source of stars’ tremendous energy.

Superimposed is an image of the sun’s surface ( image details). In this major event from 2002, the sun blasts over a billion tons of matter downwards.

Tell me why the stars do shine origin