His research explores the many modes of interaction between radiation and matter: from the evolution of hydrogen and helium in the early universe to the study of the structure of stars. He is very fond of unstable stars - ones that pulsate regularly and allow us to determine distances to other galaxies. Most recently his research has led him to explore the nature of planets orbiting other stars. He has discovered a few such planets - with novel techniques that he hopes to use to find planets like Earth.
He is the director of the new Harvard Origins of Life Initiative - a multidisciplinary center bridging scientists in the physical and in the life sciences, intent to study the transition from chemistry to life and its place in the context of the Universe.