Colloquium

What the most metal-poor stars tell us about the early Universe

Dr. Anna Frebel
McDonald Observatory
University of Texas at Austin

Wednesday, November 5, 2008   4:00 p.m.  NSH 118

(Refreshments at 3:30 p.m. NSH 202)

 

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 now also employed to test theoretical predictions about the formation of the very first low-mass stars as well as the initial mass function of the first stars themselves.