Christopher Hirata, professor of astronomy and physics, received this year's Helen B. Warner Prize for observational or theoretical research from the American Astronomical Society - the premier award for young astronomers. Hirata is cited for his remarkable cosmological studies, particularly his observational and theoretical work on weak gravitational lensing, one of the most important tools for assessing the distribution of mass in the universe. His work on cosmological recombination, structure formation, and dark energy and cosmic acceleration, and the extraordinary depth of understanding he brings to these subjects is facilitating the next generation of important cosmological experiments.