The Planets - Neptune

Updated February 21, 2017 | Factmonster Staff

Neptune, named for an ancient Roman sea god, is a stormy blue planet about 30 times farther from the Sun than Earth. Neptune was discovered when astronomers realized that something was exerting a gravitational pull on Uranus, and that it was possible that an unknown planet might be responsible. Through mathematical calculations, astronomers determined there was indeed an undiscovered planet out in space—a year before it was actually seen for the first time through a telescope (in 1846).

  • Size: Almost 4 times the size of Earth in diameter
  • Diameter: 30,775 miles (49,528 km)
  • Surface: A liquid layer covered with thick clouds and with constant, raging storms
  • Atmosphere: Hydrogen, helium, methane, and ammonia
  • Temperature: –353°F (–214°C)
  • Rotation of its axis: 16 hours and 7 minutes
  • Rotation around the Sun: 165 Earth years
  • Your weight: Not known
  • Distance from Earth: 2,680,000,000 miles at closest point
  • Mean Distance from Sun: 2,796.46 million miles (4,497 million km)
  • Satellites: 13
  • Rings: 4
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