Rolf Kudritzki
Institute for Astronomy, University of Hawaii at Manoa

"Extragalactic Stellar Astronomy with the Brightest Stars in the Universe"

A supergiants are massive stars in transitions from the blue to the red (and
vice versa) in the uppermost HRD. They are the intrinsically brightest
"normal" stars at visual light in the universe with absolute visual magnitudes
up to -9, i.e. one single object can be as bright as a dwarf galaxy. They
are ideal to study young stellar populations in galaxies beyond the Local
Group. We use them as tools to determine chemical composition and galactic
and stellar evolution, interstellar extinction, reddening laws and distances.
The talk will summarize our knowledge of these objects based on high spectral
resolution studies in the Milky Way and Local Group. It will then present most
recent results on the quantitative spectral analysis of such objects in
galaxies beyond the Local Group based on medium and low resolution spectra
obtained with the ESO VLT and Keck. We will describe the analysis method,
discuss the determination of metallicity and metallicity gradients and we will
introduce a new method to measure accurate extragalactic distances based
on the stellar gravities and effective temperatures obtained. Finally, we
will discuss the perspectives of future work using the the giant
ground-based telescopes of the next generation such as the TMT, the GMT and
the E-ELT.