Ancient, gold-rich stars may contain clues to galaxy formation

Space.com : Scientists have been puzzled by the discovery of a number of ancient stars that contain unusually high levels of heavy elements such as gold, platinum, and uranium, because the heaviest elements are usually found at those levels only in much later generations of stars. Helium, hydrogen, and lithium were the first elements to form in the early universe. Heavier elements, up to iron in the periodic table, formed later inside stars. And the heaviest elements formed in supernovae. After a few hundred million years, all the known chemical elements existed, but the oldest stars that are still around today should contain only a fraction of the amount of heavy elements seen in the Sun and younger stars. Using data from the Nordic Optical Telescope (NOT), astronomers from the Niels Bohr Institute in Copenhagen and Michigan State University have found evidence to support one of two theories that seek to explain the anomaly. In one theory, the anomalous enrichment came from the stars’ binary companions. In the other theory, which is more consistent with the NOT data, the enrichment comes from a previous generation of stars that seeded the local interstellar medium. “What this tells is how new elements and new stars formed in infant galaxies and why the sun, planets and we ended up having the chemical composition we do,” said Terese Hansen , lead author on a paper published in Astrophysical Journal Letters.