Jim Truran
Department of Astronomy and Astrophysics, Enrico Fermi Institute, U. Chicago
Tracing the Abundance History of the Cosmos

The primordial compositions of galaxies reflect that of the Universe as it emerged from the cosmological Big Bang: hydrogen, deuterium, 3He, 4He, and 7Li. Within galaxies, stars and supernovae play the dominant role in synthesizing the elements from carbon through uranium and in returning heavy-element-enriched matter to the interstellar gas from which new stars are formed. This abundance history is written in the compositions of stars in our Galaxy (and other galaxies). We review the nuclear processes that participate in heavy element synthesis, identify the astrophysical sites (stars and supernovae) with which they are associated, and note particularly the (production) timescales on which this enrichment is expected to occur. We then demonstrate how observations of often distinctive abundance patterns in old (low metallicity) stellar populations can be used to trace and to constrain the star formation and nucleosynthesis histories of galaxies and the Universe.