vault of heaven vs apex of the sun's way

vault of heaven and apex of the sun's way both are nouns.

Word	Noun	Adjective	Verb	Adverb
vault of heaven	Yes	No	No	No
apex of the sun's way	Yes	No	No	No

vault of heaven (noun)	apex of the sun's way (noun)
the apparent surface of the imaginary sphere on which celestial bodies appear to be projected	the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars