polestar vs North Star

polestar and North Star both are nouns.

Word	Noun	Adjective	Verb	Adverb
polestar	Yes	No	No	No
North Star	Yes	No	No	No

As nouns, polestar and North Star are synonyms defined as:

polestar and North Star: the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it

Other synonyms of polestar include polar star, Polaris, pole star.

polestar (noun)	North Star (noun)
the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it	the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it