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| Fig. 1: Statue depicting Sir Fred Hoyle at the Institute of Astronomy. (Source: Wikimedia Commons) |
Nucleosynthesis is a process by which new atomic nuclei are constructed from existing protons and neutrons. The first existence of this process in the universe arose in the Big Bang, during which light elements like hydrogen, helium, and lithium were formed, eventually coalescing into the earliest stars. Once hydrogen and helium stars became large enough, heavier elements were then formed by a process known as stellar nucleosynthesis, in which the nuclear fusion at the center of stars results in new, heavier elements. The process of stellar nucleosynthesis is common and even continues to this day. A rarer process, supernova nucleosynthesis, occurs within exploding stars and is responsible for creating elements numbered from 6 (carbon) to 28 (nickel) on the periodic table, according to first reports detailed by Sir Fred Hoyle in 1954. [1]
Born June 24, 1915, in Yorkshire, England, Sir Fred Hoyle (see Fig. 1) was a renowned mathematician and physicist known for his development of the theory of supernova nucleosynthesis. A Cambridge graduate, Hoyle was a critical scientist working on radar development during WWII after his graduation. Clearly mathematically bright early in his career, Hoyle played a key role in significant scientific discoveries including steady-state universe theory as well as the theory of supernova nucleosynthesis. In reward of his scientific discoveries, Hoyle was elected to the Royal Society in 1957 and served as the director of Cambridge's Institute of Theoretical Astronomy for six years before receiving knighthood in 1972. [2]
In his groundbreaking 1954 work, Hoyle detailed that there is a general tendency for stars of higher temperatures to be breeding grounds for nuclei of increasing atomic weights. Rapid gravitational shrinkage results in a quick heating of the star, which in turn generates the conditions under which heavier elements may be forged (Fig. 2). Over the course of the Galaxy, with an age estimated on the order of 1010, it is estimated that 3 × 107 Type I supernovae have occurred. Only a minority of stars exceed the mass required to have the stellar death result in a supernova, by exceeding Chandrasekhar's Limit. [1]
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| Fig. 2: False color image of Kepler Supernova remnant from Chandra X-ray Observatory. (Courtesy of NASA. Source: Wikimedia Commons) |
Built upon the earlier work of William Fowler, Hoyle's pursuit of understanding the synthesis of nuclei from stellar activity was a successful one. In addition to yielding a Nobel Prize in 1983 for Fowler and Chandrasekhar - a famous Indian mathematician known for discovering Chandrasekhar's Limit (1.4 × the mass of the sun) - the research also resulted in the 1997 Crafoord Prize for Hoyle and fellow astrophysicist Salpeter. [3] The work of Hoyle and others enlightened the scientific community regarding the origins of the heavier elements which make up our world. The discovery of the correlation between stellar mass, temperature, and element formation was one that directed future astrophysical and chemical studies.
© Wyatt Pontius. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] F. Hoyle, "On Nuclear Reactions Occurring in Very Hot Stars. I. The Synthesis of Elements from Carbon to Nickel," Astrophys. J. Suppl. S. 1, 121 (1954).
[2] S. Minton, Fred Hoyle, A Life in Science (Cambridge University Press, 2011).
[3] S. E. Woosley, "Hoyle and Fowler's Nucleosynthesis in Supernovae," Astrophys. J. Centennial Issue 525C, 924 (1999).
