Discovering the most metal-poor Galactic halo stars


The most metal-poor objects in the Galactic halo provide important tools
to study the chemical evolution of the Milky Way and the early Universe.
I will present the recent discoveries of three important metal-poor
stars from the Hamburg/ESO survey, and discuss their impact on our
current observational knowledge of the early Universe:
1. The most-iron poor star known to date, HE 1327-2326, a
    dwarf or subgiant with [Fe/H]=-5.4.
2. HE 1300+0157, a subgiant with [Fe/H]=-3.9 and a C overabundance, and
3. HE 1523-0901, a giant for which nucleo-chronometric age dating was
    carried out based on 7 different abundance ratios including uranium.