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Basics: Planet Neptune

in: The Solar System

Author: Zhunoman

Created: 14th Feb 2022 (Edited: 14th Feb 2022)

Tags: Space Planets Moons

Neptune is the furthest planet from the Sun in the solar system. It is renowned for its deep blue color.

Key Info:

Date Discovered: 23 September 1846

Discovered By: Urbain Le Verrier, John Couch Adams, Johann Galle

Mass: 102,410,000,000,000,000,000,000,000 kg

Volume: 62,525,703,987,421 km cubed

Age: about 4.5 billion years

Diameter: 49,244 km

Basics: Planet Neptune

Main Image Credit: NASA/JPL, Published: October 30, 1998

Neptune is named after the Roman god of the sea. This could be due to its dark blue colour; it is a somewhat deeper blue than Uranus. Neptune was discovered after Uranus through the use of mathematical calculations (the first to be located in this way). 

It is the 8th, and furthest known planet (except for dwarf planets), and it cannot be seen with the naked eye. It is about 30 times further from the Sun than Earth. The ability to see the other planets with the naked eye is the reason why we do not know the discovery date of the closer planets, like Saturn and Jupiter.

It is believed Neptune took shape around the same time as Uranus. It formed near to the Sun with gravity pulling in gases and dust. It then would have reached the outer area of the solar system about 4 billion years ago.


Surface Features and Structure

Like Uranus, Neptune is an ice giant as opposed to a gas giant. It is 4 times wider than Earth, and slightly smaller than its neighbour, Uranus. Neptune however is denser and heavier than Uranus. Possibly about 80% of the planet is made from hot dense icy fluids which include water, methane and ammonia.

The planet is considered to have a hard solid core; it is believed to be about the size of earth. It does not really have a solid surface due to the very deep liquid layer. Under the cold clouds, it is believed there is a large amount of fluid. It is held there through extreme pressure.

Out of the very large planets, Neptune is the densest. Our very own planet Earth is the densest of all the solar system planets. The terrestrial planets are all denser due to the fact that they are mostly solid structures. When more study is done it will be possible to define exactly how dense the core of Neptune is.


Atmosphere of Neptune

The atmosphere of Neptune has similar materials to a star: hydrogen and helium. It also has a small amount of methane. This atmosphere extends deep into the planet until it eventually merges with the liquid layer.

In comparison to Uranus, Neptune has a much deeper blue colour. It is expected that there is some component (as yet to be discovered) that is causing this different colour (otherwise it would be greener like Uranus).

Neptune is considered to be the most violently windy planet in the whole system. The winds can be as much as 3 times more powerful than that of Jupiter, and 9 times as much as Earth. Neptune’s clouds of frozen methane have been measured moving more than 2000 km per hour across the planet. New storms have been observed forming at different points across the planet.

For a bit of fun, this video gives some info on the nature of Neptune:


Rings of Neptune

Similar to Uranus, Neptune has faint and difficult to see rings. It is said to have around 5 main rings: Galle, Leverrier, Lassell, Arago, and Adams. The planet also has something related to the rings, but referred to as arcs. Arcs are clumps of dust which are on the Adams ring. They are unique and there is debate as to how they remain so stable. The leading theory is that it is related to the shepherd moon, Galatea.

You should not expect to be able to see the rings with a telescope. It is hard enough to see any details of the planet alone, let alone the faint rings.


Moons of Neptune

Neptune has 14 known moons. One of those moons is the massive Triton which is the 7th largest in the solar system and part of the big 7. The next moon down from Triton in size is (Titania of Uranus) which is just over half the diameter. The other moons of Neptune are minute in comparison to Triton; all the other moons combined do not even come close to Triton’s size and mass. For this reason, you should not expect to be able to view any except Triton, even with a powerful telescope.

Like 4 other large moons in the solar system, Triton is geologically active. It is believed that it could have been a dwarf planet like Pluto that somehow got caught in Neptune’s gravity. This could explain the odd retrograde orbit which is unique to this one larger moon. This means that it orbits in the opposite direction to Neptune’s orbit.

As already mentioned, the shepherd moon Galatea is one of interest. It is believed to be linked to the 5 arcs on the Adams ring.


Images of Neptune

Neptune clouds, NASA/JPL, Published: January 29, 1996:


Processed image, NASA/JPL-Caltech/Kevin M. Gill, Published: August 31, 1989:



Further Reading