Astrophysics is a noun

The definition of astrophysics is a branch of astronomy that studies the composition and origin of objects in outer space along with the way they interact with each other and other matter. A person who studies black holes
And cosmic strings is an example of a person who is involved with astrophysics.

Astrophysics is a branch of space science that applies the laws of physics and chemistry to seek to understand the universe and our place in it.
The field explores topics such as :
Life and death of stars
Nebulae and other objects in the universe.

Astrophysics is a science that uses the laws of physics
And math to explain how the universe works.
Astronomy is the study of things in outer space
And different phenomena occurring in outer space.