Stardust in the Laboratory
Ernst Zinner
Washington University
In the past, almost all information about stars has come to us in the form
of electromagnetic radiation. In the last twenty years, a new source of
information on nucleosynthesis and stellar evolution has become available
in the form of preserved stardust found in primitive meteorites. These µm-
and sub-µm-sized so-called presolar grains are recognized as stardust by
their isotopic compositions, which are completely different from those of
the solar system. Whereas most of the material from many different stellar
sources that went into the making of the Solar System was thoroughly mixed,
obliterating any information about its origin, these grains preserve the
isotopic compositions of their stellar sources. They condensed in outflows
from late-type stars and in SN ejecta and were included in meteorites, from
which they can be isolated and studied for their isotopic compositions in
the laboratory. Thus these grains constitute a link between us and our stellar
ancestors. They provide new information on stellar evolution, nucleosynthesis,
mixing processes in asymptotic giant branch (AGB) stars and supernovae, and
galactic chemical evolution. Of the eight nuclear processes proposed by Burbidge
et al. to build all the elements heavier than He, signatures of all except the
r- and the x-process have been detected in presolar dust grains. Red giants,
AGB stars, Type II supernovae, and possibly novae have been identified as
stellar sources of the grains. Stardust phases identified so far include
silicates, oxides such as corundum, spinel, and hibonite, diamond, graphite,
silicon carbide, silicon nitride, titanium carbide, and Fe-Ni metal.
Astrophysics Seminar
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