At Penn State University researchers study stars and their immediate surroundings including stars of all ages, from pre-main sequence stars to stellar remnants. Observational astronomers use a variety of techniques across a broad spectrum of wavelengths, including X-ray, ultraviolet, visible, and infrared light. Recent theoretical studies have modeled the dynamics of interactions in star clusters, mass exchange between stars, stellar mergers, and the development in time of populations of binary stars.