explorer vs pole star

explorer

noun
  • One who explores something 

  • A person who by means of travel (notably an expedition) searches out new information. 

  • A visual representation of a file system etc. through which the user can navigate. 

  • Any of various hand tools, with sharp points, used in dentistry. 

pole star

noun
  • A person, principle, or thing which acts as a guide; a guiding light; also, something which attracts much attention; a centre of attention. 

  • The star visible to the naked eye which was in the past, is now, or will be in the future nearest a celestial pole of a planet. 

How often have the words explorer and pole star occurred in a corpus of books? (source: Google Ngram Viewer )