B.A., Haverford College (1969)
Ph.D., University of Texas at Austin (1973)

Research Interests
Chemical composition of stars; stellar evolution; galactic nucleosynthesis.

Group Areas
Chemical Abundances

My research involves aspects of stellar spectroscopy, and I am fortunate to have access to the excellent high-resolution spectrographs of McDonald Observatory. Within the past few years through various collaborations I have also used spectrographic instrumentation at NOAO Kitt Peak and Cerro Tololo, Keck, Lick, European Southern, Las Campanas, and Hubble Space Telescope Observatories.

I study the chemical compositions of stars. Stars generate nearly all elements of the periodic table heavier than hydrogen in their internal fusion cycles (whose primary purpose is to generate energy). The stars return their newly minted heavy elements to the interstellar medium gas clouds at the ends of their lives, either gently in stellar winds, or violently in nova or supernova explosions. Newly forming stars then gather up this enriched gas. So with each succeeding stellar generation the heavy element content builds up in the Galaxy.

I have concentrated on spectroscopic studies of old stars: either giant stars of the Galactic disk that are nearing the end of their lives, or long-lived stars of the old Galactic halo. Analysis of Galactic halo stars especially intrigues me, for these stars were born near the start of the Galaxy and therefore their chemical compositions hold vital clues to "early Galactic nucleosynthesis", or heavy element generation at the beginning of our Galaxy.