Starting the Periodic System at Light and Heavy Ends
The Big Bang filled the Universe with the primordial soup of hydrogen and heliu with a sprinkling of lithium. 10 Gyr later, when the Solar system formed, the Galax was the well-mixed result of nucleosynthesis in many generations of stars in man stages of evolution, but the detailed elemental/isotopic abundance pattern of the Solar system allow us to elucidate many parts of the story. The very earliest (=most metal-poor) stars contain the nucleosynthesis products of just a couple of generations of progenito stars; yet, with a few notable differences, their chemical composition is remarkably similar to that of the Sun.
A few stars, however, with overall metallicity o 0.1-0.2% of the Sun, have enormous overabundances of carbon (and sometimes the very heaviest elements as well, such as Th and U), relative to the iron group and below. We have asked ouselves whether these stars are jus oddballs to be ignored, or are trying to tell us something fundamental about conditions around the time our Galaxy formed? We will describe some recent result from an observing project to learn more about the way these elements formed for the first time.