Planets beyond Neptune
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Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and continued at th
Percival Lowell, originator of the Planet X hypothesis
Jacques Babinet, an early proponent of a trans-Neptunian planet
Clyde William Tombaugh
Discovery image of Charon
Neptune
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Neptune is the eighth and farthest known planet orbiting the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17
Galileo Galilei may have been the first person to sight Neptune
Urbain Le Verrier mostly successfully predicted Neptune's position
Johann Gottfried Galle was requested by Le Verrier to look for Neptune
John Couch Adams independently calculated Neptune's position