The branch of astronomy concerned with the physical and chemical properties of celestial bodies WordNet 3.0 & Open English WordNet

Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. Wikipedia

The branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. OmegaWiki

The branch of astronomy or physics that deals with the physical properties of celestial bodies and with the interaction between matter and radiation in celestial bodies and in the space between them. Wiktionary

Interdisciplinary branch of astronomy and physics. Wiktionary (translation)