Fifth planet (hypothetical) orbit as defined by the Titius–Bode law. Between 1845 and 1851, eleven additional asteroids were discovered and Jupiter had become the twentieth planet. At this point, astronomers began to classify asteroids as minor planets. Following the reclassification of the asteroids in their own group, Jupiter became the fifth planet once again. With the redefinition of the term "planet" in 2006, Ceres is now considered a dwarf planet. The disruption theory suggests that a planet which was positioned between Mars and Jupiter was destroyed, resulting in the asteroid belt between these planets. Scientists in the 20th century dubbed this hypothetical planet
The Secret of the Ninth Planet Plutonians dead, the danger to the solar system is past. Burl sees then the people of other planets and of other stars coming together in peace and mutual understanding. The book was reviewed by “When the power of the sun becomes noticeably diminished, young Burl Denning and his expedition take off in an anti-gravitational ship to discover the cause and its location. After a dizzying tour of all the planets, they realize that the trouble springs from Pluto, a belligerent planet which is trying to usurp the life-giving power which the sun gives earth. Making an alliance with the friendly