Astrophysics, the study of the universe and the laws that govern physical processes in it, have undergone several extraordinary developments in recent decades. Technological advances in instrumentation, detectors, and computing for both ground-based and orbiting observatories have led to a wealth of discoveries at wavelengths ranging from low energy radio waves to very high energy gamma-rays. By applying the laws of physics for strong, electroweak, and gravitational interactions, a coherent model of the universe has emerged. Yet it is far from complete and enigmas continue to appear. Purdue has active research programs in optical astronomy, high energy astrophysics, relativity and cosmology. Of particular theoretical interest are tests of the validity of both Newtonian gravity and General Relativity, which are being explored by several faculty members in the Physics department.