astrophysics
Astrofísica, in English, refers to 'astrophysics'. It is a branch of astronomy that deals with the physical properties of celestial bodies and the regions of space they inhabit. This includes the study of the physical properties of stars, galaxies, and the universe as a whole. Broadly, it endeavors to explain the structure and lifecycles of celestial objects, their inner workings, as well as their interactions and behavior within the larger cosmic environment.
Astrophysics is a fascinating branch of physics
This sentence uses 'astrofísica' to identify it as a particular branch of study in physics. In English, the use of is typically indicates a definition or identification.
My cousin is studying astrophysics at the university
In this sentence, 'astrofísica' is the subject of study for the speaker's cousin. Here, the person referenced (the cousin) is associated with the study of astrophysics.
The Nobel prize in astrophysics was given out yesterday
Here, 'astrofísica' is used as the particular field for a prestigious award. The use of 'in' in English denotes the specific field for the Nobel Prize.