astrophysicist vs astronomer

astrophysicist and astronomer both are nouns.

Word	Noun	Adjective	Verb	Adverb
astrophysicist	Yes	No	No	No
astronomer	Yes	No	No	No

As nouns, astronomer is a hypernym of astrophysicist; that is, astronomer is a word with a broader meaning than astrophysicist:

astrophysicist: an astronomer who studies the physical properties of celestial bodies
astronomer: a physicist who studies astronomy

Other hypernyms of astrophysicist include stargazer, uranologist.

astrophysicist (noun)	astronomer (noun)
an astronomer who studies the physical properties of celestial bodies	a physicist who studies astronomy