Astrophysics is a branch of astronomy that deals with the physics of our universe. One who studies the in this field is known as an astrophysicist.
The astrophysics department aboard the USS Enterprise-D used a newly upgraded sensor array, dubbed the "La Forge sensor array" to conduct scans of the Amargosa Diaspora in 2368. (TNG: "Schisms")
Astrophysics was one of Arjin's "better subjects." (DS9: "Playing God")
Jadzia Dax held a Premier Distinction in astrophysics. (DS9: "Dax")