the branch of astronomy concerned with the physical and chemical properties of celestial bodies
"During her lecture, Dr. Evans explained that astrophysics is the branch of astronomy concerned with the physical and chemical properties of celestial bodies by analyzing how starlight changes as it travels through space."
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.
"The graduate student spent her entire thesis analyzing how astrophysics explains the formation of stars through the interplay of gravity and thermal pressure."