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.
