The following outline is provided as an overview of and topical guide to Neptune:

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 time ...

– eighth and farthest known

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

in the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest

giant planet The giant planets constitute a diverse type of planet much larger than Earth. They are usually primarily composed of low-boiling-point materials (volatiles), rather than rock or other solid matter, but massive solid planets can also exist. The ...

. Neptune is 17 times the mass of

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

and is slightly more massive than its near-twin

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

, which is 15 times the mass of Earth and slightly larger than Neptune.Neptune is denser and physically smaller than Uranus because Neptune's greater mass gravitationally compresses the atmosphere more. Neptune orbits the Sun once every 164.8

years A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hou ...

at an average distance of . It is named after the Roman god of the sea and has the

astronomical symbol Astronomical symbols are abstract pictorial symbols used to represent astronomical objects, theoretical constructs and observational events in European astronomy. The earliest forms of these symbols appear in Greek papyrus texts of late antiq ...

♆, a stylised version of the god Neptune's

trident A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other mar ...

Classification of Neptune

Astronomical object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often u ...

** Gravitationally rounded object ***

Planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

****

Giant planet The giant planets constitute a diverse type of planet much larger than Earth. They are usually primarily composed of low-boiling-point materials (volatiles), rather than rock or other solid matter, but massive solid planets can also exist. The ...

*****

Ice giant An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two ice giants in the Solar System: Uranus and Neptune. In astrophysics and planetary ...

**** Planet of the Solar System *****

Outer planet The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

*****

Superior planet In the Solar System, a planet is said to be inferior or interior with respect to another planet if its orbit lies inside the other planet's orbit around the Sun. In this situation, the latter planet is said to be superior to the former. In the ref ...

Location of Neptune

Milky Way Galaxy The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

– barred spiral galaxy **

Orion Arm The Orion Arm is a minor spiral arm of the Milky Way Galaxy that is across and approximately in length, containing the Solar System, including Earth. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion ...

– a spiral arm of the Milky Way ***

– the Sun and the objects that orbit it, including 8 planets, the eighth and furthest planet from the Sun being Neptune **** Orbit of Neptune

Movement of Neptune

* Orbit of Neptune * Rotation of Neptune

Features of Neptune

* Atmosphere of Neptune * Rings of Neptune

Natural satellites of Neptune

Moons of Neptune The planet Neptune has 14 known moons, which are named for minor water deities in Greek mythology. By far the largest of them is Triton, discovered by William Lassell on October 10, 1846, 17 days after the discovery of Neptune itself; over a ce ...

Inner moons of Neptune

Naiad In Greek mythology, the naiads (; grc-gre, ναϊάδες, naïádes) are a type of female spirit, or nymph, presiding over fountains, wells, springs, streams, brooks and other bodies of fresh water. They are distinct from river gods, who ...

Thalassa Thalassa (; grc-gre, Θάλασσα, Thálassa, sea; Attic Greek: , ''Thálatta'') was the general word for 'sea' and for its divine female personification in Greek mythology. The word may have been of Pre-Greek origin. Mythology According to ...

* Despina * Galatea *

Larissa Larissa (; el, Λάρισα, , ) is the capital and largest city of the Thessaly region in Greece. It is the fifth-most populous city in Greece with a population of 144,651 according to the 2011 census. It is also capital of the Larissa regiona ...

* Hippocamp *

Proteus In Greek mythology, Proteus (; Ancient Greek: Πρωτεύς, ''Prōteus'') is an early prophetic sea-god or god of rivers and oceanic bodies of water, one of several deities whom Homer calls the "Old Man of the Sea" ''(hálios gérôn)''. ...

Retrograde moons of Neptune

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus'' ...

Atmosphere of Triton The atmosphere of Triton is the layer of gases surrounding Triton. The surface pressure is only 14 microbars (1.4 Pa or 0.0105mmHg), of the surface pressure on Earth, and it is composed of nitrogen, similar to those of Titan and Earth. It extend ...

* List of geological features on Triton * Halimede * Psamathe * Neso

Prograde moons of Neptune

Nereid In Greek mythology, the Nereids or Nereides ( ; grc, Νηρηΐδες, Nērēḯdes; , also Νημερτές) are sea nymphs (female spirits of sea waters), the 50 daughters of the ' Old Man of the Sea' Nereus and the Oceanid Doris, sisters ...

* Sao *

Laomedeia Laomedeia , also known as Neptune XII, is a prograde irregular satellite of Neptune. It was discovered by Matthew J. Holman, et al. on August 13, 2002. Before the announcement of its name on February 3, 2007 (IAUC 8802), it was known as S/2002 ...

History of Neptune

History of Neptune *

Discovery of Neptune The planet Neptune was mathematically predicted before it was directly observed. With a prediction by Urbain Le Verrier, telescopic observations confirming the existence of a major planet were made on the night of September 23–24, 1846, at the ...

Exploration of Neptune

Exploration of Neptune Neptune has been directly explored by one space probe, ''Voyager 2'', in 1989. , there are no confirmed future missions to visit the Neptunian system, although a tentative Chinese mission has been planned for launch in 2024. NASA, ESA, and indep ...

Flyby missions to explore Neptune

* ''

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', ...

Future of Neptune exploration

Proposed missions to explore Neptune

* '' Interstellar Express'' * Neptune Orbiter *

ODINUS ODINUS (Origins, Dynamics, and Interiors of the Neptunian and Uranian Systems) is a space mission concept proposed to the European Space Agency's Cosmic Vision programme. The ODINUS mission concept proposes to expand the Uranus orbiter and probe ...

* ''

Trident A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other mar ...

Notes

References

External links

NASA's Neptune fact sheet

from Bill Arnett's nineplanets.org
Neptune

Astronomy Cast ''Astronomy Cast'' is an educational nonprofit podcast discussing various topics in the field of astronomy. The specific subject matter of each episode shifts from week to week, ranging from planets and stars to cosmology and mythbusting. Premier ...

episode No. 63, includes full transcript.
Neptune Profile
a
NASA's Solar System Exploration site

A children's guide to Neptune. *

(The Planetary Society) {{Outline footer *