An Integrated Experimental and Theoretical Approach to Study Presolar Grains An Integrated Experimental and Theoretical Approach to Study Presolar Grains Objectives: The study of presolar grains in primitive meteorites is fundamental to understanding both the building blocks of our Solar System and the stars in the pre-solar-system environment. Since their discovery, numerous studies of presolar dust grains have provided information on the types of stellar sources that contributed to the protosolar nebula, the environments in which they condensed, their processing in the protoplanetary disk, and possible secondary alteration processes subsequent to asteroid formation. However, several unanswered questions remain: Can very low carbon and nitrogen isotope ratios in SiC grains be produced in supernova ejecta? Are novae important contributors to the presolar grain inventory? We propose a coordinated laboratory and modeling study that will help elucidate these questions and yield an unprecedented understanding of grain condensation in stellar explosions. Plan: We propose to measure isotopes of Li, Mg, Ca, and Ti in presolar grains that are likely nova or supernova condensates. The specific reasons for choosing these elements are as follows: (1) Lithium can be produced in a variety of settings including irradiation of high energy particles released from solar flares that collided with solar nebula oxygen gas and neutrino interactions in a supernova. Recently, Co-I Starrfield developed new carbonoxygen nova models that agree with observations of recent nova outbursts and predict carbon, nitrogen, silicon, aluminum, and sulfur isotope compositions of SiC grains. These same models also predict that classical carbon-oxygen novae produce copious amounts of 7Be that decays to 7Li (half-life 53 days) similar to that observed in such explosions in our galaxy. Thus, nova condensates should show extremely large 7Li/6Li ratios, which can be orders of magnitude larger than observed in mainstream SiC grains (7Li/6Li = 9-13). Our plan is to measure Li isotopes in nova candidate grains with carbon and oxygen-anomalous compositions and to use lithium as a tracer to distinguish nova
|Effective start/end date||8/15/22 → 8/14/25|
- NASA: Shared Services Center (NSSC): $487,661.00
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