GeminiFocus April 2019 - Page 5

Vinicius Placco Making Good Use of Bad Weather: Finding Metal-poor Stars Through the Clouds The Gemini telescopes played a key role in identifying low- metallicity stars in the Galaxy by gathering medium-resolution spectroscopic GMOS data for 666 bright (V <14) stars under poor weather conditions. In-depth studies of these stars provide a unique opportunity to witness not only the chemical and dynamical evolution of the Milky Way but also to identify and distinguish between a number of possible scenarios for the enrichment of star- forming gas clouds in the early Universe. Low-metallicity stars are the Rosetta Stones of stellar astrophysics. Encoded in the atmo- sphere of these low-mass, long-lived relics are the signatures of nucleosynthetic process- es, by which the first light elements were cooked up; this could have occurred as early as a few tens of millions of years after the Big Bang. The first generation of stars to be born in the Universe were formed (mostly) out of hydrogen and helium. These are thought to be massive (tens to hundreds of solar masses), short-lived, and to end their lives in an ex- plosive event that would seed the up-to-then chemically pristine Universe with most of the chemical species we know today. By studying the mass distribution of these so-called Population III (Pop. III) stars it is possible to constrain models for the chemical evolution of the Universe at high-redshifts and the formation and evolution of our Galaxy. However, most (if not all) of the Pop. III stars are long gone, and the only way to infer their existence is by observing the low-mass stars formed right after. April 2019 GeminiFocus 3