The Origin and Evolution of the Light Elements

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AST 0097945BoesgaardThe chemical composition of stars holds the answers for many of the most fundamental questions about our Universe. Although the composition of stars like the Sun is very similar to that of the Sun, the amounts of the elements lithium (Li) and beryllium (Be) show interesting star-to-star variations among solar-type stars. This non-uniformity provides a unique opportunity to probe the insides of stars through their Li and Be content; unlike most other elements that are forged by nuclear reactions inside stars, Li and Be are destroyed there. The degree of this destruction, as reflected in the surface content, provides clues about the mechanism that does the mixing between the surfaces and the interiors of stars. Several models have been proposed for this "mix-master"; each model predicts differing amounts of depletion for Li and Be so information from both elements together is required. In this work, Dr. Ann Boesgaard, at the University of Hawaii, will concentrate on Be, with a special emphasis on Be in star clusters of known age and metal content.The enrichment over time of various chemical elements in the Galaxy reveals the history of formation of massive stars and the early production of supernovae. Tracking the increase of Be over time gives sensitive information about previous generations of massive stars and supernovae. Probing both the earliest times and the intermediate ages in more detail will result in a greater understanding of the evolution of the Galaxy. Furthermore, the study of Be in star clusters of the galactic disk help to discern the evolution and mixing in the disk component of our Galaxy.This research will take advantage of two of the world's largest telescopes, the Keck-I 10-m telescope and the Subaru 8.2-m telescope at the high-altitude Mauna Kea Observatory in Hawaii. They are equipped with state-of-the-art instruments and detectors. Their high-resolution spectrometers will be used to obtain the stellar spectra. Recent sophisticated models of stellar atmospheres will be used in the data analysis. The models of stellar interiors and of galactic chemical evolution will be constrained better by the results from the high quality data that is obtained during the course of this research. When this body of work is completed we should have a more comprehensive portrait of the internal structure of stars like the Sun and how this structure changes with time, with mass, and with metal content. Furthermore, we will have a more complete picture of the chemical history of our Galaxy.***