go down vs astronomy

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

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

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

go down (verb)	astronomy (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