major planet vs minor planet

major planet

noun
  • Any of the 8 celestial bodies which orbit the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune (a celestial body that fits the 2006 IAU definition of planet). 

  • Any planet that is significantly larger and more massive than Earth, containing large amounts of hydrogen and helium, such as Jupiter and Neptune. 

minor planet

noun
  • An astronomical object in direct orbit around the Sun that is not a planet or a comet. 

How often have the words major planet and minor planet occurred in a corpus of books? (source: Google Ngram Viewer )