Abundance of elements in an early universe, showing abundances relative to hydrogen (vertical axis) plotted against the expansion and cooling of the universe over time (horizontal axis, left to right). In 1966, Robert Wagoner, William Fowler and Fred Hoyle established that significant quantities of deuterium (D) helium (He3 and He4) and lithium (Li7) can be produced when large masses of gas collapse in a small dense state. Also, that the synthesis of elements at very high temperatures over short timescales (peaks) bridge the mass gaps and produce metals of the iron group, plus a small amount of heavier elements. Published in 1967 in insOn the Synthesis of Elements at Very High Temperaturesins in Astrophysical Journal 148 by Wagoner, Fowler and Hoyle.