Neptune

For the Roman god, see Neptune (god)

Neptune is the eighth or, occasionally, the ninth Planet from the Sun due to Pluto 's Eccentric Orbit , and the outermost Gas Giant in our Solar System . Although the smallest of the gas giants, Neptune is more massive than Uranus : its stronger gravitational field has compressed it to a higher density.

Faint dark colored rings have been detected around the blue planet, but are much less substantial than those of Saturn . When these rings were discovered, it was thought that they might not be complete, but this was disproved by '' Voyager 2 ''. Neptune also has 2,500 km/h winds of Hydrogen , Helium , and Methane that gives the planet its blue appearance. At the time of the 1989 ''Voyager 2'' flyby, it had in its southern hemisphere a Great Dark Spot comparable to the Great Red Spot on Jupiter . Neptune possesses nine confirmed moons and four awaiting confirmation. Neptune's largest moon, Triton , is notable for its Retrograde Orbit , extreme cold (38 K ), and extremely tenuous (14 Microbar ) nitrogen/methane atmosphere.

Neptune is named after the Roman God Of The Sea because of its blue methane clouds. Its Astronomical Symbol is a stylized version of the god's Trident (♆).

Discovered on September 23 , 1846 , Neptune has been visited by only one spacecraft, ''Voyager 2'', which flew by the planet on August 25 , 1989 . In 2003, there was a proposal to NASA 's "Vision Missions Studies" to implement a "Neptune Orbiter with Probes" mission that does '' Cassini ''-level science without fission-based electric power or propulsion. The work is being done in conjunction with JPL and the California Institute Of Technology .

WEATHER

(top), Scooter (middle white cloud), and the Wizard's eye (bottom).]]

In 1989 , the Great Dark Spot (GDS) was discovered by NASA's Voyager 2 Spacecraft . But in 1994 , NASA's Hubble Space Telescope observed Neptune and didn't see the Great Dark Spot on the planet. Instead, a new storm similar to the old Great Dark Spot was found in the northern hemisphere of Neptune. The reason for the Great Dark Spot's disappearance is unknown, but many scientists believe heat transfer from the planet's core disrupted the atmospheric equilibrium and disrupted existing circulation patterns.

The Scooter is another storm, a white cloud south of the Great Dark Spot. The Wizard's eye is a southern hurricane on Neptune, the second intensive hurricane of Neptune

PLANETARY RINGS

See Also: Rings of Neptune

Neptune has a faint Planetary Ring system of unknown composition. The rings have a peculiar "clumpy" structure, the cause of which is not currently understood but which may be due to the gravitational interaction with small moons in orbit near them.

Evidence that the rings are incomplete first arose in the mid- 1980s , when Stellar Occultation experiments were found to occasionally show an extra "blink" just before or after the planet occulted the star. Images by ''Voyager 2'' in 1989 settled the issue, when the ring system was found to contain several faint rings. The outermost ring, Adams, contains three prominent arcs now named ''Liberté'', ''Egalité'', and ''Fraternité'' (Liberty, Equality, and Fraternity). The existence of arcs is very difficult to understand because the laws of motion would predict that arcs spread out into a uniform ring over very short timescales. The gravitational effects of Galatea , a moon just inward from the ring, are now believed to confine the arcs.

Several other rings were detected by the ''Voyager'' cameras. In addition to the narrow Adams Ring 63,000 km from the centre of Neptune, the Leverrier Ring is at 53,000 km and the broader, fainter Galle Ring is at 42,000 km. A faint outward extension to the Leverrier Ring has been named Lassell ; it is bounded at its outer edge by the Arago Ring at 57,000 km.

New Earth-based observations announced in 2005 appeared to show that Neptune's rings are much more unstable than previously thought. In particular, it seems that the ''Liberté'' ring might disappear in as little as one century. The new observations appear to throw our understanding of Neptune's rings into considerable confusion.

NATURAL SATELLITES OF NEPTUNE

See Also: Neptune's natural satellites

Neptune has 13 known Moon s. The largest by far, and the only one massive enough to be Spheroid al, is Triton , discovered by William Lassell just 17 days after the discovery of Neptune itself. Unlike all other large planetary moons, Triton has a Retrograde Orbit , indicating that it was captured, and probably represents the largest known example of a Kuiper Belt object (although clearly no longer in the Kuiper Belt). It is close enough to Neptune to be locked into a Synchronous Orbit , and is slowly spiraling inward. Triton is the coldest object that has been measured in the solar system.

Neptune's second known satellite, the irregular moon Nereid , has one of the most eccentric orbits of any satellite in the solar system.

From July to September 1989, ''Voyager 2'' discovered six new Neptunian moons. Of these, the irregularly shaped Proteus is notable for being as large as a body of its density can be without being pulled into a spherical shape by its own gravity. Although the second most massive Neptunian moon, it is only one quarter of one percent of the mass of Triton. Neptune's innermost four moons, Naiad , Thalassa , Despina , and Galatea , orbit close enough to be within Neptune's rings. The next farthest out, Larissa was originally discovered in 1981 when it had blocked a star. This was attributed to ring arcs, but when ''Voyager 2'' observed Neptune in 1989, it was found to have been caused by the moon. Five new irregular moons discovered between 2002 and 2003 were announced in 2004 (''for a timeline of discovery dates, see Timeline Of Natural Satellites ''). As Neptune was the Roman god of the sea, the planet's moons have been named after lesser sea gods.

TROJAN ASTEROIDS OF NEPTUNE

As of 2005, there are two known Trojan Asteroid s of Neptune which have the same orbital period as the planet. They lie in the elongated, curved regions around the L₄ and L₅ Lagrangian Point s 60° ahead of and behind Neptune. These are and .In 2005, three more suspected Neptune Trojans were spotted: , , and .

Classification of orbits as resonant (1:1 in this case) requires high precision orbital data which can only be obtained from a number of observations spanning a significant arc (i.e. period of time). As of April 2006, out of the last three, only and are listed by the Minor Planet Center {Link without Title} .
proved to be a scattered disk object.

APPEARANCE AND VISIBILITY FROM EARTH

Neptune is never visible with the Naked Eye . The brightness of Neptune is between Magnitudes +7.7 and +8.0, so a telescope or binoculars are required to observe it. With the use of a telescope it appears as a small blue-green disk, similar in appearance to Uranus; the blue-green colour comes from the Methane in its atmosphere.

With an orbital period of 165 years, Neptune will soon return to the approximate position in the sky where Galle discovered it. This will happen three different times. These are April 11 , 2009 , when it will be in Prograde Motion ; July 17 2009 , when it will be in Retrograde Motion ; and finally for the last time for the next 165 years, on February 7 2010 . This is explained by the concept of retrogradation. Like all planets in the solar system beyond Earth, Neptune undergoes Retrogradation at certain points during its Synodic Period . In addition to the start of retrogradation, other events within the synodic period include Astronomical Opposition , the return to Prograde Motion , and Conjunction to the Sun.

In its orbit around the Sun, Neptune will return to its original point of discovery in August 2011.

See also: Aspects Of Neptune

NEPTUNE IN FICTION AND FILM

Neptune has been used as a reference and setting in fiction and films.

The first fictional visit of Neptune, portrayed as glacial but nevertheless inhabited, occurred in '' Spirito Gentil '' (1889).

In the Captain Future series, Neptune is portayed as a sea planet, not out of any scientific theory but evidently because Neptune was the Roman sea god.

In Olaf Stapledon 's 1930 epic novel '' Last And First Men '', Neptune is the final home of the highly evolved human race.

Samuel R. Delany 's 1976 novel '' Triton '' has humanity colonizing several parts of the solar system, including Neptune's largest moon.

Neptune was the intended destination of the mining ship '' Red Dwarf '' in the books based on the BBC sitcom of that name, but an accident on board sends it into deep space instead.

The planet was the setting of the 1997 sci-fi/horror film '' Event Horizon ''.

The planet was also the home of various alien species and characters.

In H. P. Lovecraft 's '' Cthulhu Mythos '' (1928), Neptune is known as "Yaksh" and is inhabited by curious fungoid creatures ( Clark Ashton Smith 's ''The Family Tree of the Gods'', 1944).

In the anime '' Bishoujo Senshi Sailor Moon '' (1992), Sailor Neptune is the soldier representing the planet. A Pisces , she has wavy deep green hair and her image colours represent those of Neptune. On her forehead is the symbol of Neptune, which resembles a trident, Poseidon's weapon. Her attacks represent Poseidon's ocean powers (e.g. Deep Submerge). Her talisman is the Deep Aqua Mirror, also bearing the glyph and colors of Neptune.

In the animated TV series '' Futurama '' (1999-2003), Neptunian s are a purple-skinned, four-armed race of humanoids that coexist peacefully with humans across the solar system. They appear to hold two of their four arms with another Neptunian for unknown reasons. Elzar the cook, is also a Neptunian. Robot Santa 's base is also located on Neptune, in his 'Death Fortress' at the north pole of Neptune.

In the Japanese Anime '' Urusei Yatsura '' , Neptune is an icy, cold place which is the home of Oyuki, one of Lum's childhood alien friends.

It also had a Boskonian base on it in E. E. Smith's Lensman series (later destroyed by the Galactic Patrol).

In '' Space Patrol '' (1962) - episode The Slaves of Neptune - The crew of the Galasphere are sent to solve the mystery of a spaceship sending colonists to Pluto which disappeared near Neptune. On approach to Neptune Dart, Slim and Husky fall under the hypnotic influence of Neptunian overlord Tyro who is using his powers to trap Earth colonists as slaves.

In " The Venus Belt ", part of L. Neil Smith 's Alternative History series, an unrestrained Capitalist Free Enterprise culture makes a huge success of colonising the Asteroid Belt and decides to blow up and smash to pieces the "utterly useless planet" Venus so as to create a new Asteroid Belt (hence the book's name). Declaring the operation a sucess, at the very end of the book a charcter announces their intention to similarly blow up Neptune as well.

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