Neptune Facts

Neptune is the eighth planet from the Sun and the last one that we know of in our solar system. It is the third largest planet and is a beautiful blue colour. Neptune is the last planet we have discovered to date (now that Pluto is only classed as a dwarf planet) and has only been visited by a spacecraft once.

Interesting Facts about Neptune

  • Neptune was named after the Roman god of the Sea. This is because of its blue ocean like colour.
  • Neptune was first discovered in 1846. The planet was found by Jean Joseph Le Verrier. It was discovered later than all the other planets because it is not visible to the naked eye and so was not known to the ancients.
  • At first Neptune was called Le Verrier, named after the man who discovered it. This name did not stick and it was quickly renamed Neptune to fall in line with all the other planets named after Roman gods.
  • Neptune was discovered by watching the orbit of Uranus. It was seen that Uranus was being pulled from its orbit by a gravitational force at the same point each time it went around the Sun. Further investigation led scientists to find Neptune.
  • It takes 164.8 Earth years for Neptune to orbit the Sun. That is a massive 60,190 earth days! This makes it the planet that is slowest to move around the Sun. In fact in 2011 it completed its first full journey around the Sun since Neptune was first discovered in 1846.
  • Neptune is one of the Gas Giants. It is made of layers of 29% helium, 80% hydrogen and traces of methane gas. It does not have a solid surface but is thought to have a solid core, similar to the size of planet Earth.
  • Like Uranus it is sometimes called an Ice Giant because it has an inner layer of water, ammonia and methane ice.
  • Neptune has a Great Dark Spot storm. This is similar to the Great Red Spot on Jupiter. The storm itself is about the same size as planet Earth.
  • Although Neptune is slow to move around the Sun, it spins quickly on its axis making a day on Neptune 18 hours long. This is six hours less than Earth takes to rotate.
  • Neptune is 2793 million miles (4495 million kilometres) from the Sun. As far as we know it is the planet furthest away from the Sun in our Solar System.
  • Neptune is 2700 million miles (4345 kilometres) away from Earth.
  • The Voyager 2 is the only spacecraft to have reached Neptune. It flew past in 1989 and sent the first close up pictures of the planet back to Earth. Because of how far away Neptune is, it was four hours and 6 minutes before the signal reached Earth.
  • Neptune has a ring system. It is nothing quite as striking as Saturn’s ring system but it does have faint rings surrounds the planet. These are most likely made up of grains of dust and ice particles and are reddish in colour.
  • Neptune has 14 moons. The biggest of these is called Triton and was discovered a number of months after the discovery of Neptune. Triton is a very special moon as it orbits Neptunes but turns the opposite direction on its axis. This means they are spinning in opposite directions. Imagine walking around an object like a car (the Sun) whilst spinning around clockwise (Neptune) with a friend walking around you in an anti-clockwise circle (Triton).
  • Neptune’s moons are all named after Greek Water Gods. This is because Neptune is named after the main God of the Sea. The names include Neired, Proteus, Despina and Thalassa.
  • Neptune has a diameter of 29,297 miles (47,150 kilometres). This makes it the third biggest planet in the solar system.
  • Neptune is extremely cold. The planet has an average temperature of -214 degrees Celcius (-353 degrees fahrenheit) The temperature stays low most of the time because it is so far away from the Sun.
  • Neptune has a unique strong magnetic field. It is around 27 times stronger than the one on Earth. It is special compared with other planets because it is not in line with the planet’s axis and so is tipped on its side at 47 degree angle.
  • Currently there are no further missions set to explore Neptune further.

Related Neptune Questions


Picture of Planet Neptune

Image of the Planet Neptune

Neptune Quick Facts

Mass:102,410,000,000,000,000 billion kg (17.15x Earth)
Equatorial Diameter:49,528 km
Polar Diameter:48,682 km
Equatorial Circumference:155,600 km
Known Moons:14
Notable Moons:Triton
Known Rings:5
Orbit Distance:4,498,396,441 km (30.10 AU)
Orbit Period:60,190.03 Earth days (164.79 Earth years)
Surface Temperature:-201 °C
First Record:September 23rd 1846
Recorded By:Urbain Jean Joseph Le Verrier & Johann Galle