Up until the 18th century just six planets were identified in the solar system Mercury, Venus, Earth, Mars, Jupiter, Saturn. Uranus and other bodies were discovered in the 18th and early 19th centuries. In the 19th century astronomers began to realize that recently discovered bodies that had been classified as planets Vesta, Juno, Ceres, Pallas had a much smaller mass; as a result they were reclassified as "asteroids". Neptune was discovered in 1846.

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