celestial sphere vs empyrean

celestial sphere and empyrean both are nouns.

Word	Noun	Adjective	Verb	Adverb
celestial sphere	Yes	No	No	No
empyrean	Yes	Yes	No	No

As nouns, celestial sphere and empyrean are synonyms defined as:

celestial sphere and empyrean: the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

Other synonyms of celestial sphere include firmament, heavens, sphere, vault of heaven, welkin.

celestial sphere (noun)	empyrean (noun)
the apparent surface of the imaginary sphere on which celestial bodies appear to be projected	the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

celestial sphere (adjective)	empyrean (adjective)
	of or relating to the sky or heavens
	inspiring awe