Willy Fowler was also impressed with Hoyle’s prediction of the resonant level in carbon. In fact, he spent his following sabbatical in Cambridge to work with Hoyle. The collaboration between the two men and between them and the husband-and-wife team of astronomers Geoffrey and Margaret Burbidge led to one of the best-known works in astrophysics. The 1957 landmark paper by Burbidge, Burbidge, Fowler, and Hoyle—often referred to as B²FH—gave a comprehensive theory for the synthesis of all the elements heavier than boron in stars. In a way, when Joni Mitchell sang “We are stardust,” she was simply giving a concise, lyrical summary of Hoyle’s 1954 paper and that of B²FH. The four researchers used extensive astronomical data on the abundances of heavy elements in stars and meteorites and combined those with crucial nuclear data from experiments and from the hydrogen bomb test on the Eniwetok Atoll in the Pacific on November 1, 1952, to support their theoretical calculations. They described no fewer than eight nuclear processes that synthesize the elements in stars and identified the different astrophysical environments in which these processes take place. B²FH pointed out correctly that the observational evidence that “there are real differences in chemical composition between stars” provides a strong argument in favor of a stellar synthesis theory, rather than having all the elements synthesized in the big bang.

This was a genuine tour de force. The massive, 108-page paper started with a romantic touch: two contradictory quotes from Shakespeare about the question of whether the stars govern humanity’s fate. The first, from King Lear, reads: “It is the stars, the stars above us, govern our conditions.” This is followed by the words “but perhaps” preceding the second quote, from Julius Caesar: “The fault, dear Brutus, is not in our stars, but in ourselves.” The paper ended with a call to observers to make every possible effort to determine the relative abundances of different isotopes in stars, since those could truly be used to test the different nuclear reaction schemes. Figure 22 shows a picture taken at the Institute of Theoretical Astronomy in Cambridge in 1967. Fred Hoyle is in the middle of the second row, with Margaret Burbidge to his left. Willy Fowler is in the middle of the front row, with Geoff Burbidge to his right.

Figure 22

There was one thing that the B²FH paper did not achieve. No matter how hard they tried, Hoyle and his collaborators did not manage to account for the abundances of the lightest elements by forming them inside stars. Deuterium, lithium, beryllium, and boron were just too fragile—the heat in stellar interiors was sufficient for these elements to be destroyed by nuclear reactions, rather than created. Helium, the second most abundant element in the cosmos, proved to be problematic too. This may sound surprising, since stars are clearly forming helium. After all, isn’t the fusion of four hydrogens into helium the main source of power for most Sun-like stars? The difficulty turned out to be not at all with synthesizing helium in general, but with synthesizing enough of it. Detailed calculations have shown that nucleosynthesis in stars would predict for helium a cosmic abundance of only about 1 percent to 4 percent, while the observed value is about 24 percent. This left the big bang as the lone source for the lightest elements, just as Gamow and Alpher had suggested.