Astrophysics
lastmod 2015-11-05created 2015-11-051 edits
Astrophysics is a branch of astronomy and physics that studies the physical properties of celestial objects such as stars, galaxies, and interstellar matter (luminosity, density, temperature, chemical composition, etc.) and the interactions between celestial objects, using the methods of physics. It is a relatively new field within astronomy, beginning in the 19th century.
In practice, physical methods are indispensable to almost all research in modern astronomy. Therefore, distinguishing between astronomy and astrophysics has little meaning. Graduate programs in astronomy departments are sometimes classified as astronomy or astrophysics, but this merely reflects the history of the research group rather than the content of the discipline.