Fifth planet

In the history of astronomy, a handful of Solar System bodies other than Jupiter have been counted as the fifth planet from the Sun. Hypotheses There are three main ideas regarding hypothetical planets between Mars and Jupiter. Asteroids During the early 19th century, as asteroids were discovered, they were considered planets. Jupiter became the sixth planet with the discovery of Ceres in 1801. Soon, three more asteroids, Pallas (1802), Juno (1804), and Vesta (1807) were discovered. They were counted as separate planets, despite the fact that they share a single orbital spacing given by 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 August 2006, Ceres is now considered a dwarf planet. Disruption theory