Today In Science History – June 24 – Fred Hoyle and Nucleosynthesis

Fred Hoyle
Fred Hoyle was one of the best known British astronomers of the 20th Century. Credit: ESA/Cardiff University

June 24 is Fred Hoyle’s birthday. Hoyle was a well-known British astronomer who was the first to outline the creation of elements within stars.

Hoyle’s work on nucleosynthesis showed how elements greater than helium could be formed through fusion reactions within stars. His first paper showed the core temperature of stars could evolve hot enough to fuse elements up to iron. Fusion reactions build heavier elements and those elements would fuse to form even heavier elements. Eventually, the core temperature would reach an equilibrium point where iron would be more abundant than other heavy elements. This process, known as the e Process, explains why iron has such a high natural abundance. His second paper, in cooperation with three other physicists showed the creation of elements from carbon to iron required special conditions generally found in pre-supernova stars. Each element is created through fusion reactions between concentric shells of elements within the star. The paper also explained the creation of elements greater than iron through neutron capture reactions. This work forms the basis of much of the study of cosmology and stellar chemistry. This paper would be enough to earn one of the authors, William Fowler,┬ápart of the 1983┬áNobel Prize in Physics. The reason Hoyle’s contribution was ignored and left out of the Prize is still unknown.

In spite of making such a large contribution to cosmology, he is probably best known for his outspoken defense of the Steady State Universe theory. Steady State Universe theory holds the universe is constantly expanding and creating new matter in order to maintain a homogenous density. The universe has no beginning and no end. This theory competed with another new theory that suggested the universe was formed from a great explosion of a super-dense state and has been expanding and cooling ever since. This theory adopted a popular name jokingly given by Hoyle during one of his popular BBC radio broadcasts: The Big Bang. He would continue to try to find fault with Big Bang theory even after the discovery of background microwave radiation. This background radiation could be explained by Big Bang, but could not be explained by Steady State.

Hoyle would never accept Big Bang and would go to his grave in 2001 trying to discredit it. His reputation would steadily decline as he put forth several unconventional theories. One theory was the concept of panspermia. This was the idea that life began on Earth from cells that arrived from space and evolution is driven by the continual arrival of viruses arriving from comets. He was quoted to say the idea that life formed by chance from some primordial soup was “evidently nonsense of a high order”.