Following Carbon's Evolutionary Path from Nucleosynthesis to the the Solar System

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Wednesday, April 30 2008 - 12:00 pm, PDT
Stefanie Milam

Observations at millimeter/submillimeter wavelengths of various species can be used to trace the cyclic nature of molecular material, specifically carbon-based, throughout stellar evolution. Studies have shown that the carbon isotopic composition of the interstellar medium suggest a strong dependence upon nearby evolved stars and distance to the Galactic center. However, this can also be affected by the chemical composition, carbon-rich or oxygen-rich, and evolutionary status of these old stars. Observations have recently shown that oxygen-rich circumstellar envelopes have a more complex carbon-chemistry than once considered and may have played a role in interstellar carbon enrichment. As large stars evolve into planetary nebulae, molecular material shed from these objects has been shown to endure this highly destructive phase. Additionally, matter may survive from planetary nebulae into the diffuse interstellar medium as the inventories of both regions are now converging. Once gas and dust condense into new stars and planetary systems, the material is potentially recycled in a molecular form and on some level preserved. This is traced by the pristine composition of comets, meteors, and interplanetary dust particles. It has also been shown that comets undergo fragmentation events that release organic material into the solar system and may potentially “seed” planets for prebiotic chemistry. I will present some of these observational results and discuss laboratory experiments underway to help trace interstellar/cometary chemistry. 

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