Neptune Fact File


Planetary Fact Files
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This is the most distant planet from the sun, within our solar system. It is 30 times further away from the sun than Earth.

Neptune is the smallest of the ice giants and the furthest away. This means it wasn't discovered until 1846, making it the first planet to be predicted by mathematics before being sighted.

Although smaller than neighbouring Uranus, it has a larger mass.

The atmosphere of Neptune is made up of hydrogen, helium and methane gases. Most of the planet's mass is made up of a hot dense fluid of water, methane and ammonia which surrounds a rocky core.

Neptune takes 16 hours to complete a rotation of its axis and 165 Earth years to complete a single journey around the sun.

The climate on Neptune is very active, with winds reaching up to 600 metres per second. One storm was recorded in 1989 and lasted for five years!

14 moons have been identified so far. The largest is Triton, unusual for the fact it is the only moon in the solar system that travels in the opposite direction to the planet's rotation.

Uranus from the Hubble Telescope


Neptune has only been visited by one spacecraft.

This was a fly-by done by the Voyager 2 probe in 1989 as it navigated through the outer solar system.

It took Voyager 2 about ten years to reach Neptune, although its route did involve fly-bys of Jupiter, Saturn and Uranus first.

There are currently no confirmed upcoming missions to Neptune. Although the next suitable launch window is not until 2031.


Use the information above to answer these questions:

  1. Is Neptune's orbital speed faster or slower than Earth's?
  2. What factors would you need to take into account if planning a mission to Neptune?
  3. How many Neptune days are in a Neptune year?
  4. Which gas in the atmosphere of Neptune must be responsible for the planet's blue appearance? Hint: look at the main components of Saturn and what colour that appears.


To check your answers please see the answer sheet. This should only be used after attempting all questions.

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