Prof. Projjwal Banerjee

Metal-poor stars of <~ 0.8 solar masses that have [Fe/H]<~ -2.5 are thought to have formed within ~1 Gyr after the Big Bang. Because of their low mass, they have very long lifetimes and are still around today. Surface composition of these stars are a fossil record of interstellar gas in the early Galaxy from which they were formed and are crucial for studying the early Galactic and chemical evolution. Abundance patterns of elements observed in these stars provide a unique probe of studying the nucleosynthesis and understanding the nature of the first and early supernovae. Interestingly, elements heavier than Fe group such as Sr, Ba, and Pb, that are primarily produced by neutron capture processes, are ubiquitous in these stars. Furthermore, their abundance patterns show a large variation that seem to indicate that all types of neutron capture processes, (r)apid, (i)ntermediate, and (s)low, operated in the early Galaxy. The sites for neutron capture processes that can operate at such early times however, are still a major puzzle. I will discuss the current status of the sites for heavy element synthesis in the early Galaxy including recent results from my work on r, i and s process.