The evolution of massive stars is a key topic in astrophysics. The subject is important for several reasons, among them to determine the chemical evolution of galaxies, to set up distance indicators ("standard candles") in nearby galaxies, to determine the energetics of the interstellar medium, and to understand the recent "starburst" phenomenon in distant galaxies. The Principal Investigator (PI) proposes to continue work in this area by continuing recently initiated work on massive "O" stars in our Galaxy to external galaxies. This work would include a determination of brightnesses and temperatures of stars (an "H-R Diagram") for star clusters in the Magellanic Clouds and other nearby galaxies and the use of "Wolf-Rayet" stars (evolved massive stars with strong spectral emission lines) to trace the regions of recent star formation. Finally, the PI plans to investigate the properties of the galaxies in order to understand the occurrence of recently formed massive stars in them. This work is expected to add to our understanding of the conditions under which individual stars are formed in our Galaxy as well as the evolution of the "demographics" of stars in galaxies after they have been formed. ***//
