empyrean vs celestial sphere

empyrean and celestial sphere both are nouns.

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

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

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

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

empyrean (noun)	celestial sphere (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

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