A view of Neptune from the Voyager 2 spacecraft.

Planet | Neptune |

Radius (kilometers) | 24764 |

Orbital Distance from the Sun (kilometers) | 4504449769 |

Rotation Period (1=24 hours) | 0.67125 |

Mass (Million Metric Tons) | 1.024E+14 |

Density (grams/cubic centimeter) | 1.64 |

Year Discovered | 1846 |

Moons | 13 |

- Neptune takes over 163 Earth years to complete one orbit of the Sun - longer than any other planet.
- Voyager 2 is the only spacecraft to have visited Neptune, which it flew past in August 1989.
- In 1846, both John Adams of England and Urbain Le Verrier of France predicted the existence of a planet beyond Uranus based on mathematical calculations of deviations in Uranus' predicted orbit.
- In 1846, using the mathematical predictions of Urbain Le Verrier, Johann Galle at the Berlin Observatory discovered Neptune.
- Neptune receives less than 1/1000th the amount of sun light as does the Earth.
- Neptune is the smallest of the gas giant planets.
- The orbit of Neptune's moon Triton is slowly decaying and one day it will crash into Neptune
- Triton is the only large moon in the solar system whose orbit is retrograde (backwards).

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