Formation of Elements

The first indications that stars manufacture elements by nuclear reactions came in the late 1930s when Hans Bethe and C. F. von Weizsäcker independently deduced that the energy source for the Sun and stars was nuclear fusion of hydrogen in a process that formed helium. They received the Nobel prize in physics for this work.

George Gamow championed the big bang theory in the 1940s. Working with Ralph Alpher, he developed the theory that the elements formed during the big bang. With Robert Herman in the early 1950s, the pair used early computers to try to work out in detail how all the elements could have been formed during this cataclysmic period. The attempt was unsuccessful, but was one of the first large scientific problems to be tackled by computer.

Astronomers now realize that heavier elements could not have been formed in the big bang. The problem was that the universe cooled too rapidly as it expanded, and the extremely high temperatures required for nuclear reactions to occur did not last long enough for the creation of elements heavier than lithium or beryllium. By the time the universe had the raw materials to form the heavier elements, it was too cool.

In 1957, Margaret Burbidge, Geoffery Burbidge, William Fowler, and Fred Hoyle (referred to as B²FH) published a monumental paper in which they outlined the specific nuclear reactions that occur in stars and supernovas to form the heavy elements. Fowler received the 1983 Nobel Prize in physics for his role in understanding nuclear processes in stars.