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Neptune spacepedia.png
Number of Sattelites 14
Discovered by John Couch Adams
Urbain Le Verrier
Johann Gottfried Galle
Date of Discovery September 23, 1846
Atmospheric Makeup 75.5% hydrogen
18.75% helium
1.8% methane
Distance from Sun 2.79 billion miles
Diameter 30,961 miles
49,537 kilometers
Axial tilt 28.315 degrees
Orbit 183 Earthen years
Position in Solar System Eighth planet from Sun
Surface Features Gaseous atmosphere and common dust storms
Albedo (geometric) 0.405
(bond) 0.29
Aphelion 2.85 billion miles
Perihelion 2.78 billion miles
Mass of Planet 1.024 x 10^26 kg
Escape Velocity 23.45 kilometers/second

Neptune is the eighth and furthest planet from the Sun. Neptune is an ice giant like Uranus but with a darker tint of blue. Neptune was discovered September 23, 1846 by 3 astronomers: John Couch Adams, Urbain Le Verrier, and Johann Galle. Neptune has fourteen known satellites. Its biggest moon is Triton.

Neptune is famous for having the fastest wind currents in the Solar System, speeding up at a velocity of 1200 miles per hour. Neptune has 120 trillion pieces of ice discovered on October 18, 1996.


Neptune's core formed from a clump of rocky material that was around 2 ~ 5 times in Earth's mass. Its core gathered enough gas to become a Jovian planet.


Neptune's atmosphere is composed of the same materials as Uranus, methane and ammonia, with small amounts of ice in the inner atmosphere and its core composed of mostly metallic materials and rock.

Because Neptune and Uranus are so similar, they have been de-categorized from the term of gas giants like Jupiter and Saturn, and Neptune and Uranus have been categorized with the term of "ice giants" due to there being an exceptional amount of freezing compounds of carbon and ammonia in the atmosphere, which can lead to frozen water in the atmosphere and the surface.

Internal Structure[]

Structure neptune spacepedia.png

The internal structure of Neptune is similar to that of the neighboring planet of Uranus. The first layer is the mantle, which makes up the mass of Neptune. The mantle consists of a water-ammonia compound and methane. In fact, the water-ammonia compound makes up so much of the mantle, scientists refer to it as a water-ammonia ocean. The core of Neptune is mostly made up rock silicates such as iron and nickel.


Arc Rings.jpg

Neptune has its own collection of rings called the Rings of Neptune. These rings were discovered in the La Silla Observatory in Chile by Reinhold Häfner, Patrice Bouchet, and Jean Manfred. These rings very lowly dense. Even at their densest, they are only as dense as the lesser dense parts of Saturn's rings. The innermost moons in the rings include Despina, Naiad, Thalassa, and Galatea. The outermost moons in the rings include Larissa and Prometheus.

Orbit and Rotation[]

Neptune makes only one orbit around the Sun in about 168.2 earth years. This is because Neptune is more than two billion miles from the Sun.

Because of its gaseous nature, Neptune's equatorial rotation is equal to 18 Earth hours. Yet since the wind speeds towards the poles are faster, the polar rotation is equal to 12 Earth hours.


Most of the atmosphere of Neptune is made up of hydrogen, making up more than eighty percent of the atmosphere. The rest is made of helium, methane, hydrogen deuteride, and ethane.

Great Dark Spot[]

492px-Neptune's Great Dark Spot.jpg

The Great Dark Spot, is a dark spot on the surface of the planet, Neptune. This one has many similar characteristics to the more famous, and commonly mistaken for, Great Red Spot. One example of a similarity is the category of the storm, for they are both anticyclonic storms, or storms that rotate different directions than that of regular storms, which are referred to as cyclonic. The first spot was observed by the Voyager 2 probe in 1989. The interior of these spots are cloud-free compared to that of Jupiter's Great Red Spot, which densely packed with dust-filled clouds. Winds in this storm are the fastest in the Solar System, being 1500 miles per hour.



The dimensions of the GDS were estimated by scientists in 1995. The dimensions measured were 15,900 x 9870 x 8350 x 4100 miles.


In November of 1994, the Hubble Space Telescope failed to photograph the GDS, leading scientists to believe that it has disappeared. Many theories surround this disappearance - one such theory claiming that due to the high wind speeds of the cyclones, as well as their close proximity to one another, the storms all pushed themselves into different directions. Another one is that they were covered up by an abundance of dust kicked into the atmosphere.

The Northern Great Dark Spot[]

After the disappearance of the main Great Dark Spot, a new, similar spot formed the northern hemisphere of Neptune. It was given the name of the Northern Great Dark Spot, or NGDS. It is the last one remaining, and has lasted several years.



Dwarf Planets