I joined the Northwestern faculty in 1987 after earning my PhD in astronomy from UCLA and carrying out postdoctoral studies as a McCormick Fellow at the University of Chicago's Enrico Fermi Institute.  My work at Northwestern involves research, teaching, and administration in the Department of Physics and Astronomy and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).  My research focuses on the application of sensitive spectroscopic techniques to astrophysical problems in the areas of cosmology, galactic evolution, and the interstellar medium.  Using the Hubble Space Telescope and the facilities of Kitt Peak National Observatory, I specialize in the measurement of weak interstellar and extragalactic absorption lines in the optical and ultraviolet spectra of stars and quasars.  Such measurements provide important information about the composition, chemistry, structure, and physical conditions of intervening gas clouds in the Milky Way and other galaxies.  My teaching efforts at Northwestern primarily focus on freshman seminars and introductory astronomy courses - during the 2017-18 academic year, I am teaching Highlights of Astronomy (Astro 120) in the fall and Introduction to Astrobiology (Astro 111) in the spring.  My teaching efforts beyond Northwestern include video courses entitled "Experiencing Hubble: Understanding the Greatest Images of the Universe" and "A Visual Guide to the Universe" that I recently developed and recorded for the Teaching Company.

Some of my research publications (full CV here):

"The Remarkable High Pressure of the Local Leo Cold Cloud"
[2012, Astrophysical Journal, 752, 119]
"The Local Leo Cold Cloud and New Limits on a Local Hot Bubble"
[2011, Astrophysical Journal, 735, 129]
"A Cold Nearby Cloud Inside the Local Bubble"
[2006, Astrophysical Journal (Letters), 650, L67]
"The Homogeneity of Interstellar Elemental Abundances in the Galactic Disk"
[2006, Astrophysical Journal, 641, 327]

"The Rich Ultraviolet Spectrum of Vibrationally Excited Interstellar H2 Toward HD 37903"
[2001, Astrophysical Journal (Letters), 553, L59]
"The Definitive Abundance of Interstellar Oxygen"
[1998, Astrophysical Journal, 493, 222]

"Small-Scale Interstellar Medium Structure: The Remarkable Sightline Toward Mu Crucis"
[1996, Astrophysical Journal (Letters), 464, L179]
"Discovery of Interstellar NH"
[1991, Astrophysical Journal (Letters), 376, L49]
"An Upper Limit on the Microwave Background Temperature at z = 1.776"
[1986, Astrophysical Journal (Letters), 308, L37]
"Ultraviolet Interstellar Extinction Toward 1367 Stars Observed by ANS"
[1981, Astrophysical Journal, 248, 545]