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Observations and Laboratory Studies of Carbon’s Evolution throughout the Galaxy

Tuesday, November 17, 2009 - 4:00pm

UVA/NRAO Colloquium, National Radio Astronomy Observatory, Charlottesville


Stefanie N. Milam

SETI Institute

NASA Ames Research Center

Moffet Field, California 94035




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- vs. 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. Once this expelled matter, comprised of 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. Though the chemistry in these objects can also be much more complex, likely due further chemistry that occurs during their lifecycle. 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.




Recent DiscoveryNews article featuring Milam's research (Posted: December 8, 2009)

Stefanie Milam is currently investigating the formation of prebiotic species in irradiated interstellar/cometary ice analogs at the NASA Ames Astrochemistry Laboratory. Dr. Milam began pursing a career as an Astrobiologist/Astrochemist by obtaining a B.S. in Chemistry at Kansas Wesleyan University (Salina, KS) in 2002. During this time she worked at an environmental laboratory and had an internship at a local winery as an assistant winemaker and laboratory technician. Her graduate studies pushed her realm of expertise to millimeter/submillimeter astronomy while working for Prof. Lucy Ziurys at the University of Arizona (Tucson, AZ). This work introduced her to the broad field of Astrobiology, which in turn became a career focus. Her thesis included studies of comets, evolved stars, molecular clouds, and planetary nebulae. By understanding what molecules are present in these objects, one can gain a further insight of the chemistry occurring as well as other physical parameters such as temperature, density, age, and abundances. Throughout this work she became involved in NASA’s Deep Impact Ground Based observing team as well as numerous exchange programs with the NASA Astrobiology Institute. She received her Ph.D. in 2007 with the dissertation title "Following Carbon’s Evolutionary Path: From Nucleosynthesis to the Solar System." In an attempt to gain a further understanding of astronomical observations she conducted throughout graduate school, Dr. Milam opted to work in the Ames Astrochemistry laboratory with Scott Sandford studying photolysis ice chemistry. Her major publications can be found on the Publications page of the Astrophysics and Astrochemistry Lab at NASA Ames Research Center.