LPL Colloquium: Dr. Nan Liu
Laboratory Astrophysics: Isotopic and Structural Analysis of Presolar SiC
Dr. Nan Liu
Research Assistant Professor
Laboratory for Space Science, Washington University
Presolar grains, stellar relicts that predate our solar system, enable the study of bona fide stellar materials in the laboratory, where the full battery of modern micro-analytical techniques can be brought to bear on them. During the past 30 years, studies on presolar SiC grains mainly focused on the dominant population (>90%), mainstream grains, which opened up new insights into the evolution and nucleosynthesis of their parent asymptotic giant branch (AGB) stars in exquisite detail. Our knowledge of other groups of presolar SiC grains and their astronomical and astrophysical implications, however, are quite limited due to the much lower abundances of these grains (<10%). In this colloquium, I will introduce the development of an innovative method to rapidly identify these rare type presolar SiC grains by coordinated SEM-EDX and Raman analysis. I will present new NanoSIMS Ti isotopic results on supernova X grains identified by this method and their implications to dust production in supernovae and young galaxies. In addition, I will show new multi-element isotopic evidence that links 13C-enriched presolar SiC grains to J-type carbon stars and supernovae and the implication to dust production in these stars. In the spirit of broadening the application of such coordinated microanalysis, I will also discuss plans to study other presolar phases, meteoritic components, and mission-returned extraterrestrial samples.