astronomy vs astronomical

astronomy is a noun but astronomical is not a noun.

Word	Noun	Adjective	Verb	Adverb
astronomy	Yes	No	No	No
astronomical	No	Yes	No	No

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

astronomy (adjective)	astronomical (adjective)
	relating or belonging to the science of astronomy
	inconceivably large