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Anna Frebel |
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"What the most metal-poor
stars tell us about the early Universe" |
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The chemical evolution of the Galaxy and the
early Universe is a key topic in modern astrophysics. The most
metal-poor Galactic halo stars are now frequently used in an attempt
to reconstruct the onset of the chemical and dynamical formation
processes of the Galaxy. These stars are an easily-accessible local
equivalent of the high-redshift Universe, and can thus be used to
carry out near-field cosmology. The discovery of two astrophysically
very important metal-poor objects has recently lead to a significant
advance in the field. One object is the most iron-poor star yet
found (with [Fe/H]=-5.4). The other star displays the strongest
known overabundances of heavy neutron-capture elements, such as
uranium, and nucleo-chronometry yields a stellar age of ~13 Gyr.
Both stars already serve as benchmark objects for various
theoretical studies with regard to nucleosynthesis processes in the
early Galaxy. I will discuss how the abundance patterns of these and
other metal-poor stars solidify and advance our understanding of the
early Universe, and provide constraints on the nature of the first
stars, as well as their explosion mechanisms and corresponding
supernova nucleosynthesis yields. Large samples of these old objects
are also employed to test theoretical predictions about the
formation of the very first low-mass stars and the lowest observable
metallicity. I will finish the talk with showing brand-new halo-like
abundances of stars in dwarf galaxies which suggests that systems
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