The eighth planet from {{UsefulNotes/the Sun}}, '''Neptune''' was named after the Roman God of the Sea because of its blue hue. (Though Modern Greece calls it "Poseidon"). Neptune is a gas giant. Similarly to {{UsefulNotes/Jupiter}}'s Great Red Spot, Neptune has its own series of atmospheric storms collectively titled as "The Great Dark Spot." Unlike the Red Spot, the Dark Spot comes and goes; the original southern Dark Spot was discovered in 1989 and had disappeared by 1994, with another prominent spot appearing in the north some years later.

Neptune has the honor of being the first planet to be discovered with mathematics as opposed to actual astronomic observation. Fitting since it is the only planet that can never be observed from {{UsefulNotes/Earth}} without a telescope. It was first spotted way back in the 1610s by Galileo, but he mistook the planet for a fixed star due to Neptune having begun its apparent retrograde motion that same day. When predictions for {{UsefulNotes/Uranus}}'s orbits were proven to be off, it was hypothesized that another planet was exerting some gravitational force. After years of calculations, Urban Le Verrier proved Neptune's existence. [[UsefulNotes/TheMoonsOfNeptune Triton]] was found just seventeen days later.

Neptune's current claim to fame: it has the fastest winds in the solar system, as high as 2,100 km/hour. The reason for this is that despite its distance, Neptune radiates 2.61 times as much energy as it receives from the Sun.

Discoveries from the 1990s onward have shown just how profound an effect that Neptune has had on UsefulNotes/{{the Solar System}}'s structure. The inner boundary of the Kuiper Belt is defined by Neptune's gravity, and the scattered disk exists almost entirely because of Kuiper Belt objects that passed too close to the planet and were launched into eccentric orbits. In this way, Neptune is the most similar to Jupiter of any other planet.

Neptune completed its first full orbital period from its discovery in September 2010.

It would take until the 20th century to discover its ring system as well as any new moons, the bulk of which were discovered by Voyager 2. Even so, more recent observations in July of 2013 showed that the probe had missed some moons, bringing Neptune's moon count up to fourteen.

A little known fact about Neptune is that, for the first five or so years after it was discovered, it was considered the Solar System's twelth planet. The demotion of the four largest asteroids[[note]]The largest of these, Ceres, was promoted to dwarf planet after the category was created for Pluto.[[/note]] five years after Neptune's discovery bumped it up to the eighth.