astronomy vs go down

astronomy is a noun but go down is not a noun.

Word	Noun	Adjective	Verb	Adverb
astronomy	Yes	No	No	No
go down	No	No	Yes	No

astronomy (noun)	go down (noun)
the branch of physics that studies celestial bodies and the universe as a whole

astronomy (verb)	go down (verb)
	grow smaller
	stop operating
	be defeated
	be ingested
	go under
	disappear beyond the horizon
	move downward and lower, but not necessarily all the way
	be recorded or remembered