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For years, scientists have assumed that the sun is an enormous mass of hydrogen. But in a poster presentation to be delivered July 21-26 at the Meteoritical Society's annual meeting in Los Angeles, Dr. Oliver Manuel says iron, not hydrogen, is the sun's most abundant element.

Manuel, a professor of nuclear chemistry at the University of Missouri-Rolla, claims that hydrogen fusion creates some of the sun's heat, as hydrogen -- the lightest of all elements -- moves to the sun's surface. But most of the heat comes from the core of an exploded supernova that continues to generate energy within the iron-rich interior of the sun, Manuel says.

"We think that the solar system came from a single star, and the sun formed on a collapsed supernova core," Manuel says. "The inner planets are made mostly of matter produced in the inner part of that star, and the outer planets of material form the outer layers of that star."

Manuel will present his the evidence for his assertion in his poster presentation, "Why the Model of a Hydrogen-filled Sun is Obsolete." His presentation will be Monday, July 21, at the Meteoritical Society's 65th annual meeting on the University of California-Los Angeles campus. Co-authors with Manuel are Cynthia Bolon, a Ph.D. student in chemistry at UMR, and Aditya Katragada, a UMR graduate student in chemistry.

Manuel says the solar system was born catastrophically out of a supernova -- a theory that goes against the widely-held belief among astrophysicists that the sun and planets were formed 4.5 billion years ago in a relatively ambiguous cloud of interstellar dust.

Iron and the heavy element known as xenon are at the center of Manuel's efforts to change the way people think about the solar system's origins.

Manuel believes a supernova rocked our area of the Milky Way galaxy some five billion years ago, giving birth to all the heavenly bodies that populate the solar system. Analyses of meteorites reveal that all primordial helium is accompanied by "strange xenon," he says, adding that both helium and strange xenon came from the outer layer of the supernova that created the solar system. Helium and strange xenon are also seen together in Jupiter.

Manuel has spent the better part of his 40-year scientific career trying to convince others of his hypothesis. Back in 1975, Manuel and another UMR researcher, Dr. Dwarka Das Sabu, first proposed that the solar system formed from the debris of a spinning star that exploded as a supernova. They based their claim on studies of meteorites and moon samples which showed traces of strange xenon.

Data from NASA's Galileo probe of Jupiter's helium-rich atmosphere in 1996 reveals traces of strange xenon gases -- solid evidence against the conventional model of the solar system's creation, Manuel says.

Manuel first began to develop the iron-rich sun theory in 1972. That year, Manual and his colleagues reported in the British journal Nature that the xenon found in primitive meteorites was a mixture of strange and normal xenon (Nature 240, 99-101).

The strange xenon is enriched in isotopes that are made when a supernova explodes, the researchers reported, and could not be produced within meteorites.

Three years later, Manuel and Sabu found that all of the primordial helium in meteorites is trapped in the same sites that trapped strange xenon. Based on these findings, they concluded that the solar system formed directly from the debris of a single supernova, and the sun formed on the supernova's collapsed core. Giant planets like Jupiter grew from material in the outer part of the supernova, while Earth and the inner planets formed out of material from the supernova's interior.

This is why the outer planets consist mostly of hydrogen, helium and other light elements, and the inner planets are made of heavier elements like iron, sulfur and silicon, Manuel says.

Strange xenon came from the helium-rich outer layers of the supernova, while normal xenon came from its interior. There was no helium in the interior because nuclear fusion reactions there changed the helium into the heavier elements, Manuel says.

In January, Manuel presented similar findings at the American Astronomical Society's meeting in Washington, D.C. His paper, "The Origin of the Solar System with an Iron-rich Sun," and other information about Manuel's research are available on the Internet at .