Neptune

Neptune is the eight planet from the Sun and one of the two planets that cannot be seen with a telescope (the other being Pluto). It is named after Neptune, the God of Sea in Roman mythology. Neptune’s diameter is about 49,528 kilometers at the equator or nearly 4 times that of Earth.

Neptune

Neptune is 30 times as far from the Sun as Earth. It has an elliptical (oval shaped) orbit around the Sun and takes approximately 165 Earth Years to complete one full revolution. However, its rotation speed about its axis is faster than that of Earth taking 16 hours and 7 minutes to complete one full rotation.

Astronomical Symbol

Neptune’s astronomical symbol is a stylized representation of god's trident.

We know that Uranus' blue-green color is a result of the presence of methane in its atmosphere, but Neptune has a more vivid, brighter blue, so there must be an unknown component that causes the more intense color that we see. The cause of Neptune's bluish trace remains a mystery.


Discovery

Neptune was the first planet to be discovered by means of mathematics rather the observations of the night sky. Astronomer Galileo had first observedNeptune on December 27, 1612, and again on January 27, 1613. However on both occasions Galileo mistook Neptune for a fixed star when it appeared very near to Jupiter in the night sky.

In 1843, John C. Adams, an English astronomer and mathematician, began working to find the location of the unknown planet nearing Uranus. Adams predicted the planet would be about 1.6 billion kilometers farther from the sun than Uranus. Adams sent his predictions to Sir George B. Airy, the Astronomer Royal of England. Airy however did not have much confidence in Adams and did not look for the unknown planet with a telescope.

Neptune

When observed, astronomers found that Uranus didn’t travel exactly as they had expected to. French Mathematician Urbain Joseph Le Verrier proposed that the position and mass of another planet could have caused the observed changes to the orbit of Uranus. Le Verrier’s predictions were ignored by the French astronomers saying that his concepts were baseless. He then sent his predictions to Johann Gottfried Galle, the Director of Urania Observatory in Berlin. Galle and his assistant, Heinrich L. d'Arrest successfully located Neptune on their first night of searching on Sept. 23, 1846. Neptune’s largest moon, Triton was also discovered seventeen days later.

Neptune’s discovery led to a nationalistic rivalry between the French and the British over who should get credit for the discovery. However, both Adams and Le Verrier were credited with the discovery of Neptune.

On August 25, 1989, Voyager 2 became the first spacecraft to visit Neptune. It provided close-up views of Neptune, its rings and six of its moons namely Despina, Galatea, Larissa, Naiad, Proteus, and Thalassa.


Atmosphere

The atmosphere of Neptune is believed to consist of hydrogen, helium, water, and silicates. Neptune’s winds are the fastest known in the solar system, reaching up to 2000 km/h.

Neptune

Voyager 2 spacecraft also located a Great Dark Spot on the surface of Neptune, which was about half the diameter of the Great Red Spot of Jupiter. However, Neptune’s great Dark Spot is believed to have been dissipated or is being covered by the other features of Neptune’s atmosphere.

Neptune receives very little heat due to its distance from the Sun. It has a surface temperature of about -218 °C (55 K). Its core consists of molten rock and metal, surrounded by a mixture of rock, water, ammonia, and methane.