THE MOST METAL-POOR STARS -- -5.5 < [Fe/H] < -3.5
John E.Norris (Mount Stromlo & Siding Spring Observatories,
The Australian National University)
The discovery and analysis of metal-poor stars lead to insight into
conditions when the Universe and Galaxy were young. We present the rationale
for studying such objects (which become progressively rarer at lowest
abundance), with a description of their systematic discovery, culminating in
the recent analysis of two objects having [Fe/H] < -5.0, and a third which
appears to have [Fe/H] ~ -4.5. We discuss the Metallicity Distribution
Function and the abundance patterns of several elements. As one proceeds to
lowest abundance one finds astounding overabundances of some or all of the
CNO group and the lighter alpha elements. While this diversity among the
most metal-poor stars has yet to be fully understood, there exists a
rapidly-increasing number of suggested models, which will be briefly
addressed.
