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Kodolányi János, a Max Planck Kémia Intézet kutatójának előadására: Presolar Grains – Stellar dust at your fingertips
Helyszín: Zoom, regisztráció: https://forms.gle/zm4DhF1pBbzEKrLQ7
Időpont: 2020. május 4. 17.00 óra
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További információ: cszabo@elte.hu; aradi.laszloelod@ttk.elte.hu

Presolar Grains – Stellar dust at your fingertips
János Kodolányi
Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
Email: j.kodolanyi@mpic.de, janos.kodolanyi@gmail.com

Fossil stellar dust grains, i.e., solid condensates that formed in the winds of red giant stars and at the wake of stellar explosions prior to the formation of the Solar System, and survived early Solar System processing, are commonly called presolar grains. Presolar grains are, thus, direct samples of stellar matter. Presolar grains are mostly less than a few hundred nanometres in diameter, and their abundance in primitive Solar System materials (unequilibrated chondrite matrices, interplanetary dust particles, and cometary dust) rarely exceeds a few hundred parts per million by volume. They are identified based on their isotope composition which, for one or more constituent elements, is more anomalous relative to the Solar System or terrestrial average, than any known material of unequivocally Solar System origin (for most grains and isotope systems, depletions/enrichments relative to the solar/terrestrial composition exceed several percent). From this it follows that the presolar grain record is biased towards the isotopically anomalous grains, and that the study of presolar grains is intimately linked to advancements in isotope analytical techniques. Based on their chemistry, most presolar grains are either carbon- or oxygen-rich, but presolar grains with neither carbon nor oxygen as a major constituent (e.g., metal grains) also exist. Since some presolar phases (e.g., silicates) are more prone to destruction by irradiation, aqueous alteration or heating than others (e.g., SiC), the abundance ratios of different presolar phases in primitive Solar System materials are variable. The most abundant carbon- and oxygen-rich presolar grain types (SiC and silicates, respectively) bear the isotopic fingerprints of nucleosynthesis in low- and intermediate mass stars, as expected from astronomical observations on dust production, but grains of supernova origin are also important part of the presolar grain record, especially among graphite grains and silicates. Since their first identification decades ago, presolar grains have been delivering invaluable information about stellar nucleosynthesis (e.g., temperature, reaction rates, neutron density), grain condensation in different stellar environments (e.g., gas density, condensation time scale), the chemical evolution of the Milky Way (e.g., origin of peaks in the abundance of elements as a function of atomic number), and about the evolution of the solar protoplanetary disc (e.g., parent body alteration). In my talk, I would like to share some basic knowledge on these ancient, extra-solar objects, and on the impact of presolar grain research on astrophysics and cosmochemistry.