Geocheminar fall-2014
Why you should be interested in the laboratory study of tiny dust grains from stars
Oct. 28, 2014,
noon - 1 p.m.
Slichter 3853
Presented By:
Ernst Zinner
Washington University
In the last 25 years a new way to study the stars has become available: the analysis of stardust in the laboratory. Primitive meteorites contain tiny dust grains that condensed in stellar outflows and explosions. These grains can be isolated from the meteorites and studied in detail in the laboratory. The stellar origin of these grains is evidenced by their isotopic compositions, which are completely different from those of the Solar System. We can measure the isotopic ratios of the major elements, as well as of many minor and trace elements, with secondary ion mass spectrometry (SIMS) in single grains that range in size from a couple of 100 nm to several µm. Such detailed isotopic analysis of individual stardust grains has provided a wealth of information on stellar nucleosynthesis, stellar mixing, and galactic chemical evolution. In addition to isotopic analysis one can study the mineralogy of stardust grains by several microanalytical techniques. Examples are transmission electron microscopy in connection with energy dispersive X-ray analysis and electron diffraction analysis, Auger spectroscopy, Raman spectroscopy, and Synchrotron radiation analysis. Examples of each will be given. Finally, I will present examples of isotopic measurements in silicon carbide grains from core-collapse supernovae that present evidence for short neutron pulses with high neutron densities