Marc Pinsonneault, professor of astronomy, is one of the world’s most accomplished stellar astrophysicists. His research focuses on theoretical models of stellar structure and evolution, emphasizing stellar rotation, helio– and asteroseismology and solar neutrinos. His work shows that rotation of stars drives flows of material and energy within them as they age, affecting their lifetimes and the chemical elements visible at their surfaces. These effects play important roles in understanding observed populations of stars and in testing the physics of the Big Bang.