How is energy produced in a star? That question has intrigued many for centuries. If scientists could learn about energy production in the stars, they might be able to apply that knowledge to the development of commercially efficient systems for energy production on Earth.

Today, scientists believe that energy is produced in stars by means of nuclear fusion, the process by which two nuclei are joined to make one nucleus, with the release of huge amounts of energy. The idea that nuclear fusion might explain stellar energy release goes back at least seventy years, to the writings of the American physicist William Draper Harkins (1873-1951), the Dutch physicists R. d'E. Atkinson and F. G. Houtermans, and the French physicist Jean Baptiste Perrin.

German physicist Hans Bethe presented the clearest development of this idea in about 1938. Bethe worked out a series of reactions by which six hydrogen...