Astronomers use ESO telescope to prove stellar origin of heavy elements
French and Belgian astronomers using a telescope at the European southern observatory in La Silla, Chile, to study three binary stars have discovered that each one contains an amount of lead weighing the same as the moon. The findings support theories about the formation of heavy elements that explain how metals such as lead and tungsten appeared on earth. Stars have been compared to nuclear 'factories' where new and progressively heavier elements are made by an ongoing process known as nucleosynthesis. In these so-called 'element factories,' nuclear fusion creates heavier elements by smashing together the nuclei of lighter ones. First, hydrogen atoms fuse to create helium. As the stars age and use up their nuclear fuel, the helium is fused into carbon. The process continues make heavier and heavier elements until a natural limit is reached when iron is formed. Elements heavier than iron cannot be formed through nuclear fusion. The production of such substances takes place by adding neutrons to the atomic nuclei. These neutral particles do not feel any electrical repulsion from the charged nuclei, and can therefore approach them unimpeded to create heavier nuclei. Scientists believe there are two places where this can occur - inside very large stars when they explode as supernovae and, more commonly, in normal stars at the end of their lives before they burn out. Computer models predict that the latter process could be particularly efficient in stars with a relatively low content of lighter metals. It is thought that lead produced by low-metallicity stars in this way was later dispersed and was present in the cloud of dust and gas from which the solar system and hence our earth was formed The astronomers made the breakthrough discovery using the Coude Echelle Spectrometer on the ESO 3.6 metre telescope at La Silla. Sophie Van Eck from the Institute of Astronomy and Astrophysics at the Free University of Brussels, Belgium, said: 'Our discovery of these lead stars is without any doubt the clearest signature of that model prediction we have today. The excellent agreement between predicted and observed abundances reinforces our current understanding of the detailed operations of the [process] in the deep interiors of the stars, and thus constitutes an important piece of information on how the heaviest stable elements in the universe are formed.'