Astrophysics
Astrophysics is the branch of astronomy that deals with the physical properties of celestial bodies and with the interaction between matter and radiation in the interior of celestial bodies and in interstellar space. It is an application of the theories and methods of physics to the study of stellar structure, stellar evolution, the origin of the solar system, and related problems of cosmology. The distinction between astrophysics and modern astronomy is disappearing in scientific usage.