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  • Neptune has the distinction of being the first planet to be discovered by mathematical prediction rather than observation. Alexis Bouvard, a French astronomer, hypothesized its existence because of irregularities in Uranus' orbit.
  • Using Bouvard's predictions, Johann Galle first observed Neptune through a telescope in 1846.
  • Neptune is the 8th and farthest planet from the Sun.
  • Neptune was named for the Roman god of the sea.
  • The 4 gas giants are Jupiter, Saturn, Neptune and Uranus. These 4 planets are sometimes referred to as the Jovian or outer planets.
  • Neptune is the smallest of the Jovian planets.
  • Neptune is not a terrestrial planet.
  • If the Sun were hollow roughly 750,000 planets the size of Neptune would fit inside.
  • The Earth's gravity is measured as 1 unit of gravity. The gravity on all other planets is taken as a multiple of Earth's.
  • Neptune's gravity is 1.21 or 1.21 times stronger than on Earth.
  • A 100 lb person would weigh 121 lbs on Neptune.
  • A day on Neptune is a little over 16 hours.
  • A year on Neptune is nearly 165 Earth years long. No human will ever live long enough to witness a complete Neptunian year!
  • The distance from the Sun to the Earth is 1 AU and is used to measure distance in our Solar System. Neptune is a whopping 30.1 AU from the Sun, or 30.1 times farther from the Sun than the Earth.
  • It takes the light from the Sun roughly 246 minutes (over 4 hours) to reach Neptune.
  • Neptune rotates in a counterclockwise motion or from West to East, same as the Earth. If you could stand on Neptune's clouds, the Sun would rise in the East and set in the West, same as on Earth.
  • Neptune's atmosphere is similar to Jupiter's in that it is primarily composed of hydrogen and helium but it also contains a higher proportion of "ices" such as water, ammonia and methane.
  • Because of these "ices" Neptune is referred to as one of the two ice giants in our Solar System - the other ice giant is Uranus.
  • The methane "ices" in the outermost regions are partly responsible for the planet's blue appearance.
  • Neptune has 13 moons that we know of. There are probably many more waiting to be discovered.
  • Neptune has active and visible weather patterns, like Jupiter, and for a time even had a Great Dark Spot, comparable to Jupiter's Giant Red Spot.
  • Neptune is the windiest planet in the Solar System. Winds can reach speeds of up to 1931 km/hour (1,200 miles/hour).
  • Neptune has 6 faint and fragmented rings that circle the planet. These rings were first detected in the 1960s but not indisputably confirmed until 1989 by Voyager II.