FRED HOYLE may have missed out on some of the credit for the theory of how stars formed the elements by leaving a simple equation out of a 1954 paper. Here he is on the campus of the California Institute of Technology in Pasadena in February 1967. Image: Courtesy of Donald Clayton
Sir Fred Hoyle, the late astrophysicist acclaimed for developing the theory of how stars forge hydrogen and helium into the heavier elements found throughout the universe, did not get the credit he deserved for a 1954 paper that outlined the idea, because he failed to spell out a key equation, a former colleague says.
Hoyle, who died in 2001 at the age of 86, was something of a tragic figure in science. Unlike the vast majority of cosmologists, he never accepted the big bang theory of the universe, preferring the idea of an unchanging or steady state cosmos. And in his later years he embraced the view that life on Earth originated in outer space. When journals refused to accept his papers exploring the idea, he reached out to the public directly by writing books for a popular audience.
Long before descending into scientific infamy, Hoyle made what should have been a lasting contribution with a 1954 Astrophysical Journal paper laying out a process by which stars heavier than 10 suns would burn hydrogen and helium at their cores into heavier elements through a progressively hotter series of nuclear fusion reactions. As such a star aged, it would end up structured like an onion, with the heaviest elements (iron and nickel) at the core and layers of progressively lighter elements toward the surface. When the star finally exploded in a supernova, it would scatter these elements into space, where they would seed still-forming star systems.
Prior to Hoyle's work, most experts believed that the elements had been born in a flurry of nuclear fusion during the big bang (now dated to around 13.7 billion years ago).
But instead of citing the 1954 study, Clayton says, researchers discussing fusional element formation, or nucleosynthesis, typically reference a 1957 paper co-authored by Hoyle and three colleagues, which went into greater detail but on other facets of the problem, says Donald Clayton, professor emeritus of physics and astronomy at Clemson University in South Carolina.
At a recent conference commemorating the 50th anniversary of that paper, known as B2FH for the initials of its authors (Geoffrey and Margaret Burbidge, now at the University of California, San Diego, along with the late Willy Fowler of the California Institute of Technology and Hoyle), Clayton said that of 30 major nucleosynthesis papers published between 1960 and 1973, 18 cited B2FH and only one gave the nod to Hoyle's 1954 paper.
Writing in Science, Clayton attributes the misplaced citation to the fact that neither paper included a relatively straightforward equation that was implicit in Hoyle's 1954 work. "Hoyle's equation," as Clayton calls it, relates the mass of heavy elements ejected by dying stars to the rate of their death and the change in abundance of the various isotopes produced during successive nuclear reactions.
"He was an expert mathematician. It's a shame he didn't decide to just write the equation," says Clayton, who was a student of Fowler's and collaborated with both Hoyle and him. A pithy equation gives other researchers "something to hang their hat on." Now researchers most likely cite B2FH without having read the founding papers in detail, he adds.
Stanford Woosley, an astrophysicist at the University of California, Santa Cruz, and the organizer of the recent B2FH conference, notes that more than half a dozen researchers "contributed unique and important insights to the founding of nuclear astrophysics," including each of the B2FH authors. "But I agree," he notes, "that Hoyle's 1954 paper is underappreciated and undercited."
In Clayton's view, Hoyle missed his chance to secure his legacy in 1957 when he and Fowler, fresh from an astronomy conference at the Vatican, were editing a draft of the paper written by the Burbidges. The finished product "was a great paper, but they did not go over the ground Hoyle had laid out," says Clayton, who adds, "Hoyle was never very interested in proofreading."