star system vs stars

star system

noun
  • A group of stars (and possibly smaller bodies such as planets or asteroids) that orbit one another. 

  • A method of creating, promoting and exploiting movie stars in cinema, emphasizing on their images rather than acting. 

stars

noun
  • Outer space. 

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