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Encyclopedia > Neptune
Neptune
Neptune from Voyager 2
Discovery
Discovered by Urbain Le Verrier
Johann Galle
Discovery date September 23, 1846[1]
Epoch J2000
Aphelion 4,553,946,490 km
30.44125206 AU
Perihelion 4,452,940,833 km
29.76607095 AU
Semi-major axis 4,503,443,661 km
30.10366151 AU
Eccentricity 0.011214269
Orbital period 60,190[4] days
164.79 years
Synodic period 367.49 day[5]
Average orbital speed 5.43 km/s[5]
Mean anomaly 267.767281°
Inclination 1.767975°
6.43° to Sun's equator
Longitude of ascending node 131.794310°
Argument of perihelion 265.646853°
Satellites 13
Physical characteristics
Equatorial radius 24,764 ± 15 km[6][7]
3.883 Earths
Polar radius 24,341 ± 30 km[6][7]
3.829 Earths
Flattening 0.0171 ± 0.0013
Surface area 7.6408×109 km²[4][7]
14.98 Earths
Volume 6.254×1013 km³[5][7]
57.74 Earths
Mass 1.0243×1026 kg[5]
17.147 Earths
Mean density 1.638 g/cm³[5][7]
Equatorial surface gravity 11.15 m/s²[5][7]
1.14 g
Escape velocity 23.5 km/s[5][7]
Sidereal rotation
period
0.6713 day[5]
16 h 6 min 36 s
Equatorial rotation velocity 2.68 km/s
9,660 km/h
Axial tilt 28.32°[5]
North pole right ascension 19h 57m 20s[6]
North pole declination 42.950°[6]
Albedo 0.290 (bond)
0.41 (geom.)[5]
Surface temp.
1 bar level
0.1 bar
min mean max
72 K[5]
55 K[5]
Apparent magnitude 8.0 to 7.78[5][8]
Angular diameter 2.2—2.4″[5][8]
Atmosphere[5]
Scale height 19.7 ± 0.6 km
Composition
 80±3.2% Hydrogen (H2) 19±3.2% Helium 1.5±0.5% Methane ~0.019% Hydrogen deuteride (HD) ~0.00015% Ethane Ices: Ammonia Water Ammonium hydrosulfide(NH4SH) Methane (?)

Discovered on September 23, 1846,[1] Neptune was the first planet found by mathematical prediction rather than regular observation. Unexpected changes in the orbit of Uranus led astronomers to deduce the gravitational perturbation of an unknown planet. Neptune was found within a degree of the predicted position. The moon Triton was found shortly thereafter, but none of the planet's other 12 moons were discovered prior to the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989. is the 266th day of the year (267th in leap years) in the Gregorian calendar. ... 1846 was a common year starting on Thursday (see link for calendar). ... Gravity redirects here. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ... Triton (trye-tÉ™n, IPA: , Greek Î¤ÏÎ¯Ï„Ï‰Î½), or Neptune I, is the planet Neptunes largest moon. ... Neptune (top) and Triton (bottom), 3 days after the Voyager 2 flyby. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... is the 237th day of the year (238th in leap years) in the Gregorian calendar. ... Year 1989 (MCMLXXXIX) was a common year starting on Sunday (link displays 1989 Gregorian calendar). ...

Neptune's atmosphere is primarily composed of hydrogen and helium along with traces of methane. The methane in the atmosphere, in part, accounts for the planet's blue appearance.[11] Neptune also has the strongest winds of any planet in the solar system, measured as high as 2,100 kilometres per hour (1,300 mph).[12] At the time of the 1989 Voyager 2 flyby, its southern hemisphere possessed a Great Dark Spot comparable to the Great Red Spot on Jupiter. Neptune's temperature at its cloud tops is usually close to −218 °C (55.1 K), one of the coldest in the solar system, due to its great distance from the Sun. The temperature in Neptune's centre is about 7,000 °C (7,270 K), which is comparable to the Sun's surface and similar to most other known planets. Neptune has a faint and fragmented ring system, which may have been detected during the 1960s but was only indisputably confirmed by Voyager 2.[13] For other uses, see Atmosphere (disambiguation). ... This article is about the chemistry of hydrogen. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... Methane is a chemical compound with the molecular formula . ... Categories: Stub | Colors ... Kilometres per hour (American spelling: kilometers per hour) is a unit of both speed (scalar) and velocity (vector). ... Miles per hour is a unit of speed, expressing the number of international miles covered per hour. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of a spacecraft. ... The Great Dark Spot as seen from Voyager 2 The Great Dark Spot was a dark spot on Neptune similar in appearance to Jupiters Great Red Spot. ... A false-color image of the Great Red Spot of Jupiter from Voyager 1. ... For other uses, see Jupiter (disambiguation). ... For other uses, see Celsius (disambiguation). ... For other uses, see Kelvin (disambiguation). ... A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ...

## History

### Discovery

Main article: Discovery of Neptune

Galileo's drawings show that he first observed Neptune on December 28, 1612, and again on January 27, 1613; on both occasions, Galileo mistook Neptune for a fixed star when it appeared very close—in conjunction—to Jupiter in the night sky.[14] Hence he is not credited with Neptune's discovery. During the period of his first observation in December 1612, it was stationary in the sky because it had just turned retrograde that very day. This apparent backward motion is created when the orbit of the Earth takes it past an outer planet. Since Neptune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with Galileo's small telescope.[15] Neptune The discovery of the planet Neptune on September 23, 1846 was a dramatic incident in the history of astronomy that also led to a tense international dispute over priority. ... Galileo redirects here. ... is the 362nd day of the year (363rd in leap years) in the Gregorian calendar. ... Events January 20 - Mathias becomes Holy Roman Emperor. ... is the 27th day of the year in the Gregorian calendar. ... Events January - Galileo observes Neptune, but mistakes it for a star and so is not credited with its discovery. ... A fixed star is a celestial object that does not seem to move (in comparison to the other stars of the night sky). ... Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ... This article does not cite any references or sources. ...

In 1821, Alexis Bouvard published astronomical tables of the orbit of Uranus.[16] Subsequent observations revealed substantial deviations from the tables, leading Bouvard to hypothesize that an unknown body was perturbing the orbit through gravitational interaction. In 1843, John Couch Adams calculated the orbit of a hypothesized eighth planet that would account for Uranus' motion. He sent his calculations to Sir George Airy, the Astronomer Royal, who asked Adams for a clarification. Adams began to draft a reply but never sent it and did not aggressively pursue work on the Uranus problem.[17][18] Alexis Bouvard (June 27, 1767 - June 7, 1843) was a French astronomer, born in Contamines, France. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... For other uses, see Uranus (disambiguation). ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ... Gravity redirects here. ... John Couch Adams (June 5, 1819 â€“ January 21, 1892), was a British mathematician and astronomer. ... For other uses, see Uranus (disambiguation). ... George Biddell Airy Sir George Biddell Airy FRS (July 27, 1801â€“January 2, 1892) was an English mathematician and astronomer, Astronomer Royal from 1835 to 1881. ... Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. ...

Urbain Le Verrier, the mathematician who codiscovered Neptune.

In the wake of the discovery, there was much nationalistic rivalry between the French and the British over who had priority and deserved credit for the discovery. Eventually an international consensus emerged that both Le Verrier and Adams jointly deserved credit. However, the issue is now being re-evaluated by historians with the rediscovery in 1998 of the "Neptune papers" (historical documents from the Royal Observatory, Greenwich), which had apparently been misappropriated by astronomer Olin J. Eggen for nearly three decades and were only rediscovered (in his possession) immediately after his death.[22] After reviewing the documents, some historians now suggest that Adams does not deserve equal credit with Le Verrier. Since 1966 Dennis Rawlins has questioned the credibility of Adams's claim to co-discovery. In a 1992 article in the journal Dio he deemed the British claim "theft".[23] "Adams had done some calculations but he was rather unsure about quite where he was saying Neptune was", said Nicholas Kollerstrom of University College London in 2003.[24][25] Royal Observatory, Greenwich. ... Olin Jeuck Eggen (July 9, 1919 â€“ October 2, 1998) was an American astronomer. ... Dennis Rawlins (1937 Baltimore, Maryland, U.S. â€“) is an American astronomer, historian, and publisher, known [1] for his intellect and acerbic wit. ... Affiliations University of London Russell Group LERU EUA ACU Golden Triangle G5 Website http://www. ...

### Naming

Shortly after its discovery, Neptune was referred to simply as "the planet exterior to Uranus" or as "Le Verrier's planet". The first suggestion for a name came from Galle, who proposed the name Janus. In England, Challis put forth the name Oceanus.[26] Roman bust of Janus, Vatican. ... Oceanus, with his wife, Tethys, ruled the seas before Poseidon. ...

Claiming the right to name his discovery, Le Verrier quickly proposed the name Neptune for this new planet, while falsely stating that this had been officially approved by the French Bureau des Longitudes.[27] In October, he sought to name the planet Le Verrier, after himself, and he was patriotically supported in this by the observatory director, François Arago. However, this suggestion met with stiff resistance outside France.[28] French almanacs quickly reintroduced the name Herschel for Uranus, after that planet's discoverer Sir William Herschel, and Leverrier for the new planet.[29] The Bureau des Longitudes is a French scientific institution, founded by decree of June 25, 1795 and charged with the improvement of nautical navigation, standardisation of time-keeping, geodesy and astronomical observation. ... FranÃ§ois Arago FranÃ§ois Jean Dominique Arago (February 26, 1786 â€“ October 2, 1853) was a French mathematician, physicist, astronomer, and politician. ... For other persons named William Herschel, see William Herschel (disambiguation). ...

Struve came out in favor of the name Neptune on December 29, 1846, to the Saint Petersburg Academy of Sciences.[30] Soon Neptune became the internationally accepted name. In Roman mythology, Neptune was the god of the sea, identified with the Greek Poseidon. The demand for a mythological name seemed to be in keeping with the nomenclature of the other planets, all of which, except for Uranus and Earth, were named for Roman gods.[31] Friedrich Georg Wilhelm von Struve (1793-1864) Friedrich Georg Wilhelm von Struve (Russian: Vasily Yakovlevich Struve) (April 15, 1793 â€“ November 23, 1864 (Julian calendar: November 11)) was a Baltic-German astronomer from a famous dynasty of astronomers. ... is the 363rd day of the year (364th in leap years) in the Gregorian calendar. ... 1846 was a common year starting on Thursday (see link for calendar). ... Saint Petersburg (Russian: Санкт-Петербу́рг, English transliteration: Sankt-Peterburg), colloquially known as Питер (transliterated Piter), formerly known as Leningrad (Ленингра́д, 1924–1991) and Petrograd (Петрогра́д, 1914–1924), is a city located in Northwestern Russia on the delta of the river Neva at the east end of the Gulf of Finland... A head of Minerva found in the ruins of the Roman baths in Bath Roman mythology, the mythological beliefs of the people of Ancient Rome, can be considered as having two parts. ... Genoese admiral Andrea Doria as Neptune, by Agnolo Bronzino. ... Neptune reigns in the city of Bristol. ...

### Status

From its discovery until 1930, Neptune was the farthest known planet. Upon the discovery of Pluto in 1930, Neptune became the penultimate planet, save for a 20-year period between 1979 and 1999 when Pluto fell within its orbit. However, the discovery of the Kuiper belt in 1992 led many astronomers to debate whether or not Pluto should be considered a planet in its own right or as part of the belt's larger structure. In 2006, the International Astronomical Union defined the word "planet" for the first time, reclassifying Pluto as a "dwarf planet" and making Neptune once again the last planet in the Solar System. For other uses, see Pluto (disambiguation). ... The Kuiper belt, derived from data from the Minor Planet Center. ... IAU redirects here. ... The final definition left the solar system with eight planets. ... Artists impression of Pluto (background) and Charon (foreground). ...

## Composition and structure

A size comparison of Neptune and Earth.

### Internal structure

Neptune's internal structure resembles that of Uranus. Its atmosphere forms about 5–10% of its mass and extends perhaps 10–20% of the way towards the core, where it reaches pressures of about 10 GPa. Increasing concentrations of methane, ammonia, and water are found in the lower regions of the atmosphere.[34] For other uses, see Uranus (disambiguation). ... For other uses, see Pascal. ... Methane is a chemical compound with the molecular formula . ... For other uses, see Ammonia (disambiguation). ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

The internal structure of Neptune.

Gradually this darker and hotter region condenses into a superheated liquid mantle, where temperatures reach 2–5,000 K. The mantle is equivalent to 10–15 Earth masses, and is rich in water, ammonia, methane, and other compounds.[1] As is customary in planetary science, this mixture is referred to as icy even though it is a hot, highly dense fluid. This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean.[35] At a depth of 7,000 km, the conditions may be such that methane decomposes into diamond crystals that then precipitate toward the core.[36] Image File history File linksMetadata Neptune-Int. ... Image File history File linksMetadata Neptune-Int. ... Earth cutaway from core to exosphere. ... Volatiles are that group of compounds with low boiling points (see volatile) that are associated with a planets or moons crust and/or atmosphere. ...

The core of Neptune is composed of iron, nickel and silicates, with an interior model giving a mass about 1.2 times that of the Earth.[37] The pressure at the centre is 7 Mbar—millions of times more than that on the surface of the Earth, and the temperature may be 5,400 K.[34][38] The planetary core consists of the innermost layer(s) of a planet. ... For other uses, see Iron (disambiguation). ... For other uses, see Nickel (disambiguation). ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. ... This article is about Earth as a planet. ...

### Atmosphere

At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium.[34] A trace amount of methane is also present. Prominent absorption bands of methane occur at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue,[39] although Neptune's vivid azure differs from Uranus's milder aquamarine. Since Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour.[11] Categories: Stub | Colors ... Aquamarine is a color, a shade between green and cyan. ...

Neptune's atmosphere is divided into two main regions; the lower troposphere, where temperature decreases with altitude, and the stratosphere, where temperature increases with altitude. The boundary between the two, the tropopause, occurs at a pressure of 0.1 bars.[40] The stratosphere then gives way to the thermosphere at a pressure lower than 10−4–10−5 microbars.[40] The thermosphere gradually trasitions to the exosphere. Atmosphere diagram showing the mesosphere and other layers. ... Atmosphere diagram showing stratosphere. ... The tropopause is between the troposphere and the stratosphere. ... The thermosphere is the layer of the earths atmosphere directly above the mesosphere and directly below the exosphere. ... [fAgot png|thumb|200px|right|Atmosphere diagram showing the exosphere and other layers. ...

A band of high altitude clouds is shown casting shadows on Neptune's lower cloud deck.

Models suggest that Neptune's troposphere is banded by clouds of varying compositions depending on altitude. The upper level clouds occur at pressures below one bar, where the temperature is suitable for methane to condense. For pressures between one and five bars, clouds of ammonia and hydrogen sulfide are believed to form. Above a pressure of five bars, the clouds may consist of ammonia, ammonium sulfide, hydrogen sulfide and water. Deeper clouds of water ice should be found at pressures of about 50 bars, where the temperature reaches 0 C. Underneath, clouds of ammonia and hydrogen sulfide may be found.[41] Ammonium sulfide, (NH4)2S, is obtained, in the form of micaceous crystals, by passing hydrogen sulfide mixed with a slight excess of ammonia through a well-cooled vessel; the hydrosulfide NH4Â·HS is formed at the same time. ... Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ...

High altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are also high altitude cloud bands that wrap around the planet at constant latitude. These circumferential bands have widths of 50–150 km, and lie about 50–110 km above the cloud deck.[42]

Neptune's spectra suggest that its lower stratosphere is hazy due to condensation of products of ultraviolet photolysis of methane, such as ethane and acetylene.[34][40] The stratosphere is also home to trace amounts of carbon monoxide and hydrogen cyanide.[40][43] The stratosphere of Neptune is warmer than that of Uranus due to elevated concentration of hydrocarbons.[40] Spectra are conditions or values that vary over a continuum. ... Photolysis refers to any chemical reaction in which a compound is broken down by light. ... R-phrases , , , , S-phrases , , , , Flash point Flammable gas Related Compounds Related oxides carbon dioxide; carbon suboxide; dicarbon monoxide; carbon trioxide Supplementary data page Structure and properties n, Îµr, etc. ... R-phrases , , , , . S-phrases , , , , , , , , . Flash point âˆ’17. ...

For reasons that remain obscure, the planet's thermosphere is at an anomalously high temperature of about 750 K.[44][45] The planet is too far from the Sun for this heat to be generated by ultraviolet radiation. One candidate for a heating mechanism is atmospheric interaction with ions in the planet's magnetic field. Other candidates are gravity waves from the interior that dissipate in the atmosphere. The thermosphere contains traces of carbon dioxide and water, which may have been deposited from external sources such as meteorites and dust.[41][43] For other uses, see Ultraviolet (disambiguation). ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ...

### Magnetosphere

Neptune also resembles Uranus in its magnetosphere, with a magnetic field strongly tilted relative to its rotational axis at 47° and offset at least 0.55 radii (about 13,500 kilometres) from the planet's physical centre. Before Voyager 2's arrival at Neptune, it was hypothesised that Uranus's tilted magnetosphere was the result of its sideways rotation. However, in comparing the magnetic fields of the two planets, scientists now think the extreme orientation may be characteristic of flows in the planets' interiors. This field may be generated by convective fluid motions in a thin spherical shell of electrically conducting liquids (probably a combination of ammonia, methane and water)[41] resulting in a dynamo action.[46] A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... For the indie-pop band, see The Magnetic Fields. ... This article is about rotation as a movement of a physical body. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... In science and engineering, conductors, such as copper or aluminum, are materials with atoms having loosely held valence electrons. ... Dynamo, or Dinamo, may refer to: Dynamo, an electrical generator Dynamo (sports society) of the Soviet Union Operation Dynamo, the 1940 mass evacuation at Dunkirk Dynamo, the rock band based in Belfast Dynamo theory, a theory relating to magnetic fields of celestial bodies Dynamo Open Air, annual heavy metal music...

The magnetic field at the equatorial surface of Neptune is estimated at 1.42 μT, for a magnetic moment of 2.16×1017 Tm3. Neptune's magnetic field has a complex geometry that includes relatively large contributions from non-dipolar components, including a strong quadrupole moment that may exceed the dipole moment in strength. By contrast, Earth, Jupiter and Saturn only have relatively small quadrupole moments and their fields are less tilted from the polar axis. The large quadrupole moment of Neptune may be the result of offset from the planet's center and geometrical constraints of the field's dynamo generator.[47][48] SI unit. ... A bar magnet. ... Schematic quadrupole magnet(four-pole) used to focus particle beams in a particle accelerator. ... In physics, the magnetic moment of an object is a vector relating the aligning torque in a magnetic field experienced by the object to the field vector itself. ...

Neptune's bow shock, where the magnetosphere begins to slow the solar wind, occurs at a distance of 34.9 times the radius of the planet. The magnetopause, where the pressure of the magnetosphere counterbalances the solar wind, lies at a distance of 23–26.5 times the radius of Neptune. The tail of the magnetosphere extends out to at least 72 times the radius of Neptune, and very likely much further.[47] In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... A magnetopause flows along the boundary between a magnetic field, (see: magnetosphere) and surrounding plasma. ...

### Planetary rings

Main article: Rings of Neptune
Neptune's rings, taken by Voyager 2.

Neptune has a planetary ring system, though one much less substantial than that of Saturn. The rings may consist of ice particles coated with silicates or carbon-based material, which most likely gives them a reddish hue.[49] 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.[50] This is a list of the named rings and ring arcs of Neptune. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ... The full set of rings, photographed as Saturn eclipsed the sun from the vantage of the Cassini spacecraft on September 15, 2006 (brightness has been exaggerated in this image). ...

The first of these planetary rings was discovered in 1968 by a team led by Edward Guinan,[13][51] but it was later thought that this ring might be incomplete.[52] Evidence that the rings might have gaps first arose during a stellar occultation in 1984 when the rings obscured a star on immersion but not on emersion.[53] Images by Voyager 2 in 1989 settled the issue by showing several faint rings. These rings have a clumpy structure,[54] the cause of which is not currently understood but which may be due to the gravitational interaction with small moons in orbit near them.[55] A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. ... Edward Guinan is currently a professor in Villanova Universitys Department of Astronomy and Astrophysics. ... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ...

The outermost ring, Adams, contains five prominent arcs now named Courage, Liberté, Egalité 1, Egalité 2, and Fraternité (Liberty, Equality, and Fraternity).[56] The existence of arcs was difficult to explain because the laws of motion would predict that arcs would spread out into a uniform ring over very short timescales. Astronomers now believe that the arcs are corralled into their current form by the gravitational effects of Galatea, a moon just inward from the ring.[57][58] A simulated view of Galatea orbiting Neptune Galatea (gal-a-tee-a, Greek Î“Î±Î»Î±Ï„ÎµÎ¯Î±) is the fourth known moon of Neptune, named after Galatea, one of the Nereids of Greek legend. ...

Earth-based observations announced in 2005 appeared to show that Neptune's rings are much more unstable than previously thought. Images taken from the W. M. Keck Observatory in 2002 and 2003 show considerable decay in the rings when compared to images by Voyager 2. In particular, it seems that the Liberté arc might disappear in as little as one century.[59] Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... The W. M. Keck Observatory is home to two of the largest optical/near-infrared telescopes in the world, at the 4,145 meter (13,600 ft) summit of Mauna Kea in Hawaii. ... Also see: 2002 (number). ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...

## Climate

One difference between Neptune and Uranus is the typical level of meteorological activity. When the Voyager 2 spacecraft flew by Uranus in 1986, that planet was visually quite bland. In contrast Neptune exhibited notable weather phenomena during the 1989 Voyager 2 fly-by.[60]

The Great Dark Spot (top), Scooter (middle white cloud),[61] and the Small Dark Spot (bottom).

Neptune's weather is characterized by extremely dynamic storm systems, with winds reaching supersonic speeds of up to around 600 m/s.[62] More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in the easterly direction to 325 m/s westward.[63] At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles.[41] Most of the winds on Neptune move in a direction opposite the planet's rotation.[64] The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is believed to be a "skin effect" and not due to any deeper atmospheric processes.[40] At 70° S latitude, a high speed jet travels at a speed of 300 m s−1.[40] Image File history File links Size of this preview: 547 Ã— 553 pixelsFull resolution (547 Ã— 553 pixel, file size: 21 KB, MIME type: image/jpeg)A close up shot of Neptunes spots taken by Nasa (The voyager). ... Image File history File links Size of this preview: 547 Ã— 553 pixelsFull resolution (547 Ã— 553 pixel, file size: 21 KB, MIME type: image/jpeg)A close up shot of Neptunes spots taken by Nasa (The voyager). ... The Great Dark Spot as seen from Voyager 2 The Great Dark Spot was a dark spot on Neptune similar in appearance to Jupiters Great Red Spot. ... Great Dark Spot (top), Scooter (middle white cloud), and Dark Spot 2 (bottom). ... A United States Navy F/A-18E/F Super Hornet in transonic flight. ... Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ...

The abundance of methane, ethane and acetylene at Neptune's equator is 10–100 times greater than at the poles. This is interpreted as evidence for upwelling at the equator and subsidence near the poles.[40]

In 2007 it was discovered that the upper troposphere of Neptune's south pole was about 10 °C (283 K) warmer than the rest of Neptune, which averages approximately −200 °C (73.1 K).[65] The warmth differential is enough to let methane gas, which elsewhere lies frozen in Neptune's upper atmosphere, leak out through the south pole and into space. The relative 'hot spot' is due to Neptune's axial tilt, which has exposed the south pole to the Sun for the last 40 Neptunian years, a Neptunian year being 165 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the south pole will be darkened and the north pole illuminated, causing the methane release to shift to the north pole.[66] In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ... Sol redirects here. ...

Because of seasonal changes, the cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo. This trend was first seen in 1980 and is expected to last until about 2020. The long orbital period of Neptune results in seasons lasting forty years.[67]

### Storms

The Great Dark Spot, as seen from Voyager 2.

In 1989, the Great Dark Spot, an anti-cyclonic storm system spanning 13,000 × 6,600 km,[60] was discovered by NASA's Voyager 2 spacecraft. The storm resembled the Great Red Spot of Jupiter. However, on November 2, 1994, the Hubble Space Telescope did not see the Great Dark Spot on the planet. Instead, a new storm similar to the Great Dark Spot was found in the planet's northern hemisphere.[68] Image File history File links GDS_Neptune. ... Image File history File links GDS_Neptune. ... The Great Dark Spot as seen from Voyager 2 The Great Dark Spot was a dark spot on Neptune similar in appearance to Jupiters Great Red Spot. ... In meteorology, an anticyclone (that is, opposite to a cyclone) is a weather phenomenon in which there is a descending movement of the air and a high pressure area over the part of the planets surface affected by it. ... The National Aeronautics and Space Administration (NASA) (IPA [ËˆnÃ¦sÉ™]) is an agency of the United States government, responsible for the nations public space program. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... A false-color image of the Great Red Spot of Jupiter from Voyager 1. ... is the 306th day of the year (307th in leap years) in the Gregorian calendar. ... Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ...

The Scooter is another storm, a white cloud group further south than the Great Dark Spot. Its nickname is due to the fact that when first detected in the months before the 1989 Voyager 2 encounter it moved faster than the Great Dark Spot.[64] Subsequent images revealed even faster clouds. The Small Dark Spot is a southern cyclonic storm, the second most intensive storm observed during the 1989 encounter. It initially was completely dark, but as Voyager 2 approached the planet, a bright core developed and can be seen in most of the highest resolution images.[69] Great Dark Spot (top), Scooter (middle white cloud), and Dark Spot 2 (bottom). ...

Neptune's dark spots are thought to occur in the troposphere at lower altitudes than the brighter cloud features,[70] so they appear as holes in the upper cloud decks. As they are stable features that can persist for several months, they are thought to be vortex structures.[42] Often associated with dark spots are brighter, persistent methane clouds that form around the tropopause layer.[71] The persistence of companion clouds shows that some former dark spots may continue to exist as a cyclone even though they are no longer visible as a dark feature. Dark spots may also dissipate either when they migrate too close to the equator or possibly through some other unknown mechanism.[72] Atmosphere diagram showing the mesosphere and other layers. ... The tropopause is between the troposphere and the stratosphere. ...

## Orbit and rotation

The average distance between Neptune and the Sun is 4.55 billion km (about 30.1 times the average distance from the Earth to the Sun, or 30.1 AU) and it completes an orbit every 164.79 years. On July 12, 2011, Neptune will have completed the first full orbit since its discovery in 1846,[80][4] although it will not appear at its exact discovery position in our sky due to the Earth being in a different location in its 365.25 day orbit. is the 193rd day of the year (194th in leap years) in the Gregorian calendar. ... 2011 (MMXI) will be a common year starting on Saturday of the Gregorian calendar. ...

The axial tilt of Neptune is 28.32°,[81] which is similar to the tilt of Earth and Mars. As a result this planet experiences similar seasonal changes. However, the long orbital period of Neptune means that the seasons last for forty Earth years.[67] Its sidereal rotation period (day) is roughly 16.11 hours long.[4] Since its axial tilt is comparable to the Earth's (23°), the variation in the length of its days over the course of its long year is not any more extreme.

Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1 hour rotation of the planet's magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System,[82] and it results in strong latitudinal wind shear.[42] Differential rotation is seen if parts of a rotating object move with different angular velocity. ...

### Orbital resonances

Main article: Kuiper belt
A diagram showing the orbital resonances in the Kuiper belt caused by Neptune: the highlighted regions are the 2/3 resonance (Plutinos), the "classical belt", with orbits unaffected by Neptune, and the 1/2 resonance (twotinos).

Neptune's orbit has a profound impact on the region directly beyond it, known as the Kuiper belt. The Kuiper belt is a ring of small icy worlds, similar to the asteroid belt but far larger, extending from Neptune's orbit at 30 AU out to about 55 AU from the Sun.[83] Much in the same way that Jupiter's gravity dominates the asteroid belt, shaping its structure, so Neptune's gravity completely dominates the Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt become destabilized by Neptune's gravity, creating gaps in the Kuiper belt's structure. The region between 40 and 42 AU is an example.[84] The Kuiper belt, derived from data from the Minor Planet Center. ... In astronomy a cubewano (pronounced ) is a Kuiper belt object that orbits beyond Neptune and is not controlled by an orbital resonance with the giant planet. ... While a Plutino completes 2 orbits around the Sun in the time it takes Neptune to complete 3 orbits, a Twotino makes 1 orbit around the Sun in the time it takes Neptune to complete 2 orbits. ... For other uses, see Asteroid (disambiguation). ... For other uses, see Asteroid (disambiguation). ... The Kuiper belt, derived from data from the Minor Planet Center. ...

There do, however, exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when an object's orbit around the Sun is a precise fraction of Neptune's, such as 1/2, or 3/4. If, say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit every time Neptune returns to its original position, and so will always be on the other side of the Sun. The most heavily populated resonant orbit in the Kuiper belt, with over 200 known objects,[85] is the 2/3 resonance. Objects in this orbit complete 1 orbit for every 1½ of Neptune's, and are known as Plutinos because the largest of the Kuiper belt objects, Pluto, lies among them.[86] Although Pluto crosses Neptune's orbit regularly, the 2/3 resonance means they can never collide.[87] Other, less populated resonances exist at 3/4, 3/5, 4/7 and 2/5.[88] In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... In astronomy, a plutino is a trans-Neptunian object that has a 3:2 orbital resonance with Neptune. ... For other uses, see Pluto (disambiguation). ...

Neptune possesses a number of trojan objects, which occupy its L4 and L5 points; gravitationally stable regions leading and trailing it in its orbit. Neptune trojans are often described as being in a 1/1 resonance with Neptune. Neptune trojans are remarkably stable in their orbits and are unlikely to have been captured by Neptune, but rather to have formed alongside it.[89] As of March 2007, there are five[1] known Neptune Trojans (named by analogy to the Trojan asteroids) which have the same orbital period as the planet. ... A contour plot of the effective potential (the Hills Surfaces) of a two-body system (the Sun and Earth here), showing the five Lagrange points. ...

## Formation and migration

Main article: Nebular hypothesis
A simulation showing Outer Planets and Kuiper Belt: a)Before Jupiter/Saturn 2:1 resonance b)Scattering of Kuiper Belt objects into the solar system after the orbital shift of Neptune c)After ejection of Kuiper Belt bodies by Jupiter

The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their evolution. One is that the ice giants were not created by core accretion but from instabilities within the original protoplanetary disc, and later had their atmospheres blasted away by radiation from a nearby massive OB star.[90] An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbirs.[91] A planetary disk forming in the Orion Nebula In this artists conception, of a planet spins through a clearing in a nearby stars dusty, planet-forming disc In cosmogony, the nebular hypothesis is the currently accepted argument about how Earths Solar System formed. ... In astrophysics, the term accretion is used for at least two distinct processes. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... OB stars are hot, massive stars stars which form in loosely organized groups called OB associations. ...

The migration hypothesis is favoured for its ability to explain current orbital resonances in the Kuiper belt, particularly the 2/5 resonance. As Neptune migrated outward, it collided with the objects in the proto-Kuiper belt, creating new resonances and sending other orbits into chaos. The objects in the scattered disc are believed to have been placed in their current positions by interactions with the resonances created by Neptune's migration.[92] A 2004 computer model by Alessandro Morbidelli of the Observatoire de la Côte d'Azur in Nice, suggested that the migration of Neptune into the Kuiper belt may have been triggered by the formation of a 1/2 resonance in the orbits of Jupiter and Saturn, which created a gravitational push that propelled both Uranus and Neptune into higher orbits and caused them to switch places. The resultant expulsion of objects from the proto-Kuiper belt could also explain the Late Heavy Bombardment 600 million years after the Solar System's formation and the appearance of Jupiter's Trojan asteroids.[93] Eris, the largest known scattered disc object (center), and its moon Dysnomia (left of center). ... The CÃ´te dAzur Observatory (in French: Observatoire de la CÃ´te dAzur) originated in 1988 with the merger of two observatories: Nice Observatory The CERGA (Centre dÃ‰tudes et de Recherches GÃ©odynamiques et Astronomiques) External links CÃ´te dAzur Observatory official website (English version) ... Time Zone CET (GMT +1) Coordinates Administration Country Region Provence-Alpes-CÃ´te dAzur Department Alpes-Maritimes (06) Intercommunality Community of Agglomeration Nice CÃ´te dAzur Mayor Jacques Peyrat (UMP) (since 1995) Statistics Land areaÂ¹ 71. ... The Late Heavy Bombardment (LHB) was a period approximately 3. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ...

## Moons

Neptune (top) and Triton (bottom).
Main article: Moons of Neptune
For a timeline of discovery dates, see Timeline of discovery of Solar System planets and their moons

Neptune's second known satellite (by order of discovery), the irregular moon Nereid, has one of the most eccentric orbits of any satellite in the solar system. The eccentricity of 0.7512 gives it an apoapsis that is seven times its periapsis distance from Neptune.[99] Nereid (IPA: , IPA: , Greek ÎÎ·ÏÎ·Î¯Î´Î±), or Neptune II, is a moon of Neptune. ...

Neptune's moon Proteus.

From July to September 1989, Voyager 2 discovered six new Neptunian moons.[47] 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.[100] 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 occulted a star. This had been 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.[101][102] As Neptune was the Roman god of the sea, the planet's moons have been named after lesser sea gods.[31] Image File history File links Size of this preview: 597 Ã— 600 pixel Image in higher resolution (836 Ã— 840 pixel, file size: 41 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Proteus (moon) List... Image File history File links Size of this preview: 597 Ã— 600 pixel Image in higher resolution (836 Ã— 840 pixel, file size: 41 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Proteus (moon) List... Atmospheric pressure 0 kPa Proteus (proe-tee-us, Greek Î ÏÏ‰Ï„Î­Î±Ï‚) is one of Neptunes moons. ... Atmospheric pressure 0 kPa Proteus (proe-tee-us, Greek Î ÏÏ‰Ï„Î­Î±Ï‚) is one of Neptunes moons. ... A simulated view of Naiad orbiting Neptune with The Sun in the distance. ... A simulated view of Thalassa orbiting Neptune. ... A simulated view of Despina orbiting Neptune Despina (des-pee-na or des-pye-na; Latin DespÅ“na from Greek Î”ÎµÏƒÏ€Î¿Î¯Î½Î·) is the third known moon of Neptune. ... A simulated view of Galatea orbiting Neptune Galatea (gal-a-tee-a, Greek Î“Î±Î»Î±Ï„ÎµÎ¯Î±) is the fourth known moon of Neptune, named after Galatea, one of the Nereids of Greek legend. ... A simulated view of Larissa orbiting Neptune Larissa (la-ris-a, Greek Î›Î¬Ïá¿‘ÏƒÎ±) is the fifth of Neptunes known moons. ...

## Observation

Neptune is never visible to the naked eye, having a brightness between magnitudes +7.7 and +8.0,[8][5] which can be outshone by Jupiter's Galilean moons, the dwarf planet Ceres and the asteroids 4 Vesta, 2 Pallas, 7 Iris, 3 Juno and 6 Hebe.[103] A telescope or strong binoculars will resolve Neptune as a small blue disk, similar in appearance to Uranus.[104] The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... For other uses, see Jupiter (disambiguation). ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ... Artists impression of Pluto (background) and Charon (foreground). ... Spectral type: G[8] Absolute magnitude: 3. ... For other uses, see Asteroid (disambiguation). ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 2 Pallas (pal-us, Greek Î Î±Î»Î»Î¬Ï‚) was the first asteroid discovered after 1 Ceres. ... 7 Iris (eye-ris) is one of the largest main belt asteroids. ... Juno (IPA: ), designated 3 Juno in the Minor Planet Center catalogue system, was the third asteroid to be discovered and is one of the largest main belt asteroids, being the second heaviest of the stony S-type. ... 6 Hebe (hee-bee, Greek â€˜Î‰Î²Î·) is a very large Main belt asteroid. ...

Because of the distance of Neptune from the Earth, the angular diameter of the planet only ranges from 2.2–2.4 arcseconds;[5][8] the smallest of the Solar System planets. Its small apparent size has made it challenging to study visually; most telescopic data was fairly limited until the advent of Hubble Space Telescope and large ground-based telescopes with adaptive optics.[105][106] The angular diameter of an object as seen from a given position is the diameter measured as an angle. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 â‰ˆ 7. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ...

From the Earth, Neptune goes through apparent retrograde motion every 367 days, resulting in a looping motion against the background stars during each opposition. These loops will carry it close to the 1846 discovery coordinates in April and July 2010 and in October and November 2011.[80] Direct motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called prograde motion. ... Opposition is a term used in positional astronomy and astrology to indicate when one celestial body is on the opposite side of the sky when viewed from a particular place (usually the Earth). ...

Observation of Neptune in the radio frequency band shows that the planet is a source of both continuous emission and irregular bursts. Both sources are believed to originate from the planet's rotating magnetic field.[41] In the infrared part of the spectrum, Neptune's storms appear bright against the cooler background, allowing the size and shape of these features to be readily tracked.[107] For other uses, see Infrared (disambiguation). ...

## Exploration

Main article: Exploration of Neptune

A Voyager 2 image of Triton

During the encounter, signals from the spacecraft required 246 minutes to reach the Earth. Hence, for the most part, the Voyager 2 mission relied on pre-loaded commands for the Neptune encounter. The spacecraft performed a near-encounter with the moon Neried before it came within 4,400 km of Neptune's atmosphere on August 25, then passed close to the planet's largest moon Triton later the same day.[109] Download high resolution version (1024x796, 150 KB)A color mosaic of Triton, Neptunes moon (large). ... Download high resolution version (1024x796, 150 KB)A color mosaic of Triton, Neptunes moon (large). ... Triton (trye-tÉ™n, IPA: , Greek Î¤ÏÎ¯Ï„Ï‰Î½), or Neptune I, is the planet Neptunes largest moon. ...

The spacecraft verified the existence of a magnetic field about the planet, and discovered that the field was offset from the center and tilted in a manner similar to the field around Uranus. The question of the planet's rotation period was settled using measurements of radio emissions. Voyager 2 also showed the Neptune had a surprisingly active weather system. Six new moons were discovered, and the planet was shown to have more than one ring.[109][47]

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.[110] The National Aeronautics and Space Administration (NASA) (IPA [ËˆnÃ¦sÉ™]) is an agency of the United States government, responsible for the nations public space program. ... Artists conceptual drawing of the future Neptune Orbiter. ... Cassiniâ€“Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... For the singer/songwriter, see Jon Peter Lewis. ... The California Institute of Technology (commonly referred to as Caltech)[1] is a private, coeducational research university located in Pasadena, California, in the United States. ...

 Solar System Portal

Image File history File links Download high resolution version (1024x1274, 113 KB) Original caption released with image This is a montage of planetary images taken by spacecraft managed by the Jet Propulsion Laboratory in Pasadena, CA. Included are (from top to bottom) images of Mercury, Venus, Earth (and Moon), Mars... Artists conceptual drawing of the future Neptune Orbiter. ... As of March 2007, there are five[1] known Neptune Trojans (named by analogy to the Trojan asteroids) which have the same orbital period as the planet. ... Planets in astrology have a different meaning to the modern astronomical understanding of what a planet is. ... The planet Neptune has been used as a reference and setting in fiction and films. ... This page is about the orchestral suite by Gustav Holst. ... Gustav Holst Gustav Holst (September 21, 1874, Cheltenham, Gloucestershire - May 25, 1934, London) [1] [2] was an English composer and was a music teacher for over 20 years. ... This page is about the orchestral suite by Gustav Holst. ...

## References

### Notes

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2. ^ a b Yeomans, Donald K. (July 13, 2006). HORIZONS System. NASA JPL. Retrieved on 2007-08-08.—At the site, go to the "web interface" then select "Ephemeris Type: ELEMENTS", "Target Body: Neptune Barycenter" and "Center: Sun".
3. ^ Orbital elements refer to the barycentre of the Neptune system, and are the instantaneous osculating values at the precise J2000 epoch. Barycentre quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis from to the motion of the moons.
4. ^ a b c d Munsell, K.; Smith, H.; Harvey, S. (November 13, 2007). Neptune: Facts & Figures. NASA. Retrieved on 2007-08-14.
5. ^ a b c d e f g h i j k l m n o p q r s Williams, David R. (September 1, 2004). Neptune Fact Sheet. NASA. Retrieved on 2007-08-14.
6. ^ a b c d e P. Kenneth, Seidelmann; Archinal, B. A.; A’hearn, M. F. et al (2007). "Report of the IAU/IAGWorking Group on cartographic coordinates and rotational elements". Celestial Mechanics and Dynamical Astronomy 90: 155–180. Springer Netherlands. doi:10.1007/s10569-007-9072-y. ISSN (Print) 0923-2958 (Print). Retrieved on 2008-03-07.
7. ^ a b c d e f g Refers to the level of 1 bar atmospheric pressure
8. ^ a b c d Espenak, Fred (July 20, 2005). Twelve Year Planetary Ephemeris: 1995–2006. NASA. Retrieved on 2008-03-01.
9. ^ Walter, Elizabeth (April 21, 2003). Cambridge Advanced Learner's Dictionary, Second Edition, Cambridge University Press. ISBN 0521531063.
10. ^ a b The mass of the Earth is 5.9736×1024 kg, giving a mass ratio of:
$begin{smallmatrix}frac{M_{Neptune}}{M_{Earth}} = frac{1.02 times 10^{26}}{5.97 times 10^{24}} = 17.09end{smallmatrix}$
The mass of Uranus is 8.6810×1025 kg, giving a mass ratio of:
$begin{smallmatrix}frac{M_{Uranus}}{M_{Earth}} = frac{8.68 times 10^{25}}{5.97 times 10^{24}} = 14.54end{smallmatrix}$
The mass of Jupiter is 1.8986×1027 kg, giving a mass ratio of:
$begin{smallmatrix}frac{M_{Jupiter}}{M_{Neptune}} = frac{1.90 times 10^{27}}{1.02 times 10^{26}} = 18.63end{smallmatrix}$
See the respective planet articles for mass references.
11. ^ a b Munsell, Kirk; Smith, Harman; Harvey, Samantha (November 13, 2007). Neptune overview. Solar System Exploration. NASA. Retrieved on 2008-02-20.
12. ^ Suomi, V. E.; Limaye, S. S.; Johnson, D. R. (1991). "High Winds of Neptune: A possible mechanism". Science 251 (4996): 929–932. AAAS (USA). doi:10.1126/science.251.4996.929.
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19. ^ a b Airy, G. B. (November 13, 1846). "Account of some circumstances historically connected with the discovery of the planet exterior to Uranus". Monthly Notices of the Royal Astronomical Society 7: 121–144. Blackwell Publishing. Retrieved on 2008-02-18.
20. ^ Challis, Rev. J. (November 13, 1846). "Account of observations at the Cambridge observatory for detecting the planet exterior to Uranus". Monthly Notices of the Royal Astronomical Society 7: 145–149. Blackwell Publishing. Retrieved on 2008-02-18.
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25. ^ Summations following the Neptune documents' 1998 recovery appeared in DIO 9.1 (1999) and William Sheehan, Nicholas Kollerstrom, Craig B. Waff (December 2004), The Case of the Pilfered Planet - Did the British steal Neptune? Scientific American.
26. ^ Moore (2000):206
27. ^ Littmann (2004):50
28. ^ Baum & Sheehan (2003):109–110
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30. ^ Hind, J. R. (1847). "Second report of proceedings in the Cambridge Observatory relating to the new Planet (Neptune)". Astronomische Nachrichten 25: 309. Retrieved on 2008-02-18. Smithsonian/NASA Astrophysics Data System (ADS).
31. ^ a b Blue, Jennifer (December 17, 2008). Planet and Satellite Names and Discoverers. USGS. Retrieved on 2008-02-18.
32. ^ See for example: Boss, Alan P. (2002). "Formation of gas and ice giant planets". Earth and Planetary Science Letters 202 (3–4): 513–523. doi:10.1016/S0012-821X(02)00808-7.
33. ^ Lovis, C.; Mayor, M.; Alibert Y.; Benz W.. "Trio of Neptunes and their Belt", ESO, May 18, 2006. Retrieved on 2008-02-25.
34. ^ a b c d Hubbard, W. B. (1997). "Neptune's Deep Chemistry". Science 275 (5304): 1279–1280. Retrieved on 2008-02-19.
35. ^ Atreya, S.; Egeler, P.; Baines, K. (2006). "Water-ammonia ionic ocean on Uranus and Neptune?" (pdf). Geophysical Research Abstracts 8: 05179.
36. ^ Kerr, Richard A. (1999). "Neptune May Crush Methane Into Diamonds". Science 286 (5437): 25. Retrieved on 2007-02-26.
37. ^ Podolak, M.; Weizman, A.; Marley, M. (1995). "Comparative models of Uranus and Neptune". Planetary and Space Science 43 (12): 1517–1522. doi:10.1016/0032-0633(95)00061-5.
38. ^ Nettelmann, N.; French, M.; Holst, B.; Redmer, R.. Interior Models of Jupiter, Saturn and Neptune (PDF). University of Rostock. Retrieved on 2008-02-25.
39. ^ Crisp, D.; Hammel, H. B. (June 14, 1995). Hubble Space Telescope Observations of Neptune. Hubble News Center. Retrieved on 2007-04-22.
40. ^ a b c d e f g h i Lunine, Jonathan I. (1993). The Atmospheres of Uranus and Neptune (PDF). Lunar and Planetary Observatory, University of Arazona. Retrieved on 2008-03-10.
41. ^ a b c d e Elkins-Tanton (2006):79–83.
42. ^ a b c Max, C. E.; Macintosh, B. A.; Gibbard, S. G.; Gavel, D. T.; Roe, H. G.; de Pater, I.; Ghez, A. M.; Acton, D. S.; Lai, O.; Stomski, P.; Wizinowich, P. L. (2003). "Cloud Structures on Neptune Observed with Keck Telescope Adaptive Optics". The Astronomical Journal, 125 (1): 364–375. Retrieved on 2008-02-27.
43. ^ a b Encrenaz, Therese (2003). "ISO observations of the giant planets and Titan: what have we learnt?". Planet. Space Sci. 51: 89–103. doi:10.1016/S0032-0633(02)00145-9.
44. ^ Broadfoot, A.L.; Atreya, S.K.; Bertaux, J.L. et.al. (1999). "Ultraviolet Spectrometer Observations of Neptune and Triton" (pdf). Science 246: 1459–1456.
45. ^ Herbert, Floyd; Sandel, Bill R. (1999). "Ultraviolet Observations of Uranus and Neptune". Planet.Space Sci. 47: 1119–1139.
46. ^ Stanley, Sabine; Bloxham, Jeremy (March 11, 2004). "Convective-region geometry as the cause of Uranus' and Neptune's unusual magnetic fields". Nature 428: 151–153. doi:10.1038/nature02376.
47. ^ a b c d Ness, N. F.; MAcuña, M. H.; Burlaga, L. F.; Connerney, J. E. P.; Lepping, R. P.; Neubauer, F. M. (1989). "Magnetic Fields at Neptune". Science 246 (4936): 1473–1478. Retrieved on 2008-02-25.
48. ^ Russell, C. T.; Luhmann, J. G. (1997). Neptune: Magnetic Field and Magnetosphere. University of California, Los Angeles. Retrieved on 2006-08-10.
49. ^ Cruikshank (1996):703–804
50. ^ Blue, Jennifer (December 8, 2004). Nomenclature Ring and Ring Gap Nomenclature. Gazetteer of Planetary. USGS. Retrieved on 2008-02-28.
51. ^ Guinan, E. F.; Harris, C. C.; Maloney, F. P. (1982). "Evidence for a Ring System of Neptune". Bulletin of the American Astronomical Society 14: 658. Retrieved on 2008-02-28.
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$begin{smallmatrix}frac{r_{ap}}{r_{per}} = frac{9.655 times 10^6 text{km}}{1.372 times 10^6 text{km}} = 7.037.end{smallmatrix}$
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### Book references

• Baum, Richard; Sheehan, William (2003). In Search of Planet Vulcan: The Ghost in Newton's Clockwork Universe. Oxford University Press. ISBN 0738208892.
• Burgess, Eric (1991). Far Encounter: The Neptune System. Columbia University Press. ISBN 0-231-07412-3.
• Cruikshank, Dale P. (1996). Neptune and Triton. University of Arizona Press. ISBN 0-8165-1525-5.
• Elkins-Tanton, Linda T. (2006). Uranus, Neptune, Pluto, and the Outer Solar System. New York: Chelsea House. ISBN 0-8160-5197-6.
• Littmann, Mark (2004). Planets Beyond, Exploring the Outer Solar System. Courier Dover Publications. ISBN 0486436020.
• Miner, Ellis D.; Wessen, Randii R. (2002). Neptune: The Planet, Rings, and Satellites. Springer-Verlag. ISBN 1-85233-216-6.
• Moore, Patrick (2000). The Data Book of Astronomy. CRC Press. ISBN 0-7503-0620-3.

Sir Patrick Moore presenting The Sky at Night, October 2005 Sir Alfred Patrick Caldwell-Moore, CBE, HonFRS, FRAS (born 4 March 1923), known as Patrick Moore, is an English amateur astronomer who has attained legendary status in British astronomy as a writer and television presenter of the subject and who...

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 Neptune (1695 words) Neptune is the outermost planet of the gas giants. Neptune was discovered on September 23, 1846 by Johann Gottfried Galle, of the Berlin Observatory, and Louis d'Arrest, an astronomy student, through mathematical predictions made by Urbain Jean Joseph Le Verrier. Neptune is a dynamic planet with several large, dark spots reminiscent of Jupiter's hurricane-like storms.
 Neptune - MSN Encarta (1656 words) Neptune’s core may be small because most of the rock composing the planet remains mixed with the vast ocean that extends upward from the core to the atmosphere. Neptune has an active atmosphere, with winds and massive storms that may be caused by heat escaping the planet’s interior. Neptune’s winds, which blow in a latitude direction, are faster in the planet’s polar regions than they are at Neptune’s equator.
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