Neptune (planet)


In astronomy, Neptune is the eighth planet from the Sun in the Solar System.  It was discovered by predictions using maths and theory, before it was actually spotted. 

The orbit of Uranus had a slight wobble (perturbation) that could only be caused by another planet near by. This planet was Neptune. It was then spotted with telescopes and confirmed.


image of Neptune as viewed from the spacecraft Voyager 2 in 1989 shows the distinct blue colour with white cloud stripes. image NASA/JPL

History of it’s discovery 

Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846  by Johann Galle within a degree of the position predicted by Urbain Le Verrier.

Adapted from: Neptune. (2016, September 18). In Wikipedia, The Free Encyclopedia. Retrieved 07:35, September 23, 2016, from

Orbit basics:

  • Distance from sun: between 4,452,940,833 and 4,553,946,490  km 
  • Orbital period (it's year):  164.79 years
  • Moons  (Natural Satellites): 13
    • Triton, largest moon (1846)
    • Faint ring

Planet basics:

  • Type of planet: Gaseous giant (ice giants)
  • Length of day: 16.11±0.01 hr
  • Average radius(equator): 24, 766±15 km
  • Mass: 102.41 x 1024 kg
  • Gravity near cloud tops: 11.15 m/s2
  • Temperature of cloud tops: 72 K (−201 °C) (extremely cold) but varies from season to season. ( 55 K (−218 °C)
  • Atmosphere: Thickness varies with depth to core, extreme wind speeds and planetary scale cyclonic storms. Recorded wind speeds as high as 2,100 km/h (580 m/s; 1,300 mph)
  • Pressure: varies according to depth to core.
  • Atmospheric composition: