Mathematical Discovery of Neptune - Another interesting history on how planets can be discovered mathematically. Neptune - From the Solar Voyager guide. Descriptions and facts about the planet Neptune. Neptune - NASA's Windows to the Universe. Neptune Facts - An article on Neptune facts, including the planet's discovery, moons, and orbit.
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Royal Greenwich Observatory - Good, up to date, introduction. Neptune - From The Nine Planets multimedia tour of the solar system. Includes Jupiter's planetary profile and vital statistics. The Discovery of Neptune - Interesting history on why it wasn't discovered sooner by the British. The Planet Neptune - good detail on this planet.