Misplaced Pages

#561438

105-423: Neptune has appeared in fiction since shortly after its 1846 discovery, albeit infrequently. It initially made appearances indirectly—e.g. through its inhabitants—rather than as a setting . The earliest stories set on Neptune itself portrayed it as a rocky planet rather than as having its actual gaseous composition ; later works rectified this error. Extraterrestrial life on Neptune is uncommon in fiction, though

210-448: A degree of the position predicted by Le Verrier. Its largest moon, Triton , was discovered shortly thereafter, though none of the planet's remaining moons were located telescopically until the 20th century. The planet's distance from Earth gives it a small apparent size , and its distance from the Sun renders it very dim, making it challenging to study with Earth-based telescopes. Only

315-431: A depth of 7,000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. Scientists believe that this kind of diamond rain occurs on Jupiter, Saturn, and Uranus. Very-high-pressure experiments at Lawrence Livermore National Laboratory suggest that the top of the mantle may be an ocean of liquid carbon with floating solid 'diamonds'. The core of Neptune

420-603: A frequency range of 50–12 kHz at magnetic latitudes 7–33˚. These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere. During Voyager 2 ’s closest approach to Neptune, the PWS instrument provided Neptune's first plasma wave detections at a sample rate of 28,800 samples per second. The measured plasma densities range from 10 – 10 cm . Neptunian lightning may occur in three cloud layers, with microphysical modelling suggesting that most of these occurrences happen in

525-519: A higher proportion of ices such as water, ammonia and methane . Similar to Uranus, its interior is primarily composed of ices and rock; both planets are normally considered "ice giants" to distinguish them. Along with Rayleigh scattering , traces of methane in the outermost regions make Neptune appear faintly blue. In contrast to the strongly seasonal atmosphere of Uranus, which can be featureless for long periods of time, Neptune's atmosphere has active and consistently visible weather patterns. At

630-410: A hot, dense supercritical fluid . This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean. The mantle may consist of a layer of ionic water in which the water molecules break down into a soup of hydrogen and oxygen ions , and deeper down superionic water in which the oxygen crystallizes but the hydrogen ions float around freely within the oxygen lattice. At

735-479: A letter and urged Berlin Observatory astronomer Galle to search with the observatory's refractor . Heinrich d'Arrest , a student at the observatory, suggested to Galle that they could compare a recently drawn chart of the sky in the region of Le Verrier's predicted location with the current sky to seek the displacement characteristic of a planet , as opposed to a fixed star. On the evening of 23 September 1846,

840-401: A low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1  bar (100  kPa ), the temperature is 72.00 K (−201.15 °C). Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from

945-409: A model of the planet's structure. Where there have been landers or multiple orbiting spacecraft, these models are constrained by seismological data and also moment of inertia data derived from the spacecraft's orbits. Where such data is not available, uncertainties are inevitably higher. The uncompressed densities of the rounded terrestrial bodies directly orbiting the Sun trend towards lower values as

1050-537: A much smaller iron core. Another Jovian moon Europa has a similar density but has a significant ice layer on the surface: for this reason, it is sometimes considered an icy planet instead. Terrestrial planets can have surface structures such as canyons , craters , mountains , volcanoes , and others, depending on the presence at any time of an erosive liquid or tectonic activity or both. Terrestrial planets have secondary atmospheres , generated by volcanic out-gassing or from comet impact debris. This contrasts with

1155-508: A new planet. In 1845–1846, Urbain Le Verrier , developed his own calculations independently from Adams, but aroused no enthusiasm among his compatriots. In June 1846, upon seeing Le Verrier's first published estimate of the planet's longitude and its similarity to Adams's estimate, Airy persuaded James Challis to search for the planet. Challis vainly scoured the sky throughout August and September. Challis had, in fact, observed Neptune

SECTION 10

#1732845626562

1260-595: A permanent home in John R. Pierce 's 1930 short story " The Relics from the Earth ". In the 1950s, the moon appeared in Margaret St. Clair 's 1950 short story " The Pillows " and Alfred Bester 's 1956 novel The Stars My Destination —albeit called "Lassell" in the latter, after its discoverer William Lassell . In the late 20th century it started receiving more attention from science fiction writers than Neptune itself. The main such work

1365-607: A solid surface, but are composed of ice and rock rather than of rock and metal. These include the dwarf planets, such as Ceres , Pluto and Eris , which are found today only in the regions beyond the formation snow line where water ice was stable under direct sunlight in the early Solar System. It also includes the other round moons, which are ice-rock (e.g. Ganymede , Callisto , Titan , and Triton ) or even almost pure (at least 99%) ice ( Tethys and Iapetus ). Some of these bodies are known to have subsurface hydrospheres (Ganymede, Callisto, Enceladus , and Titan), like Europa, and it

1470-568: A star and puts it on a collision course with Earth. In Robert William Cole 's 1900 novel The Struggle for Empire: A Story of the Year 2236 , described by science fiction scholar E. F. Bleiler as the first space opera and by Westfahl as the first appearance of a galactic empire , the vicinity of Neptune is the site of a battle between the British Empire that has come to rule the Solar System and

1575-497: A terrestrial planet is the average density its materials would have at zero pressure . A greater uncompressed density indicates a greater metal content. Uncompressed density differs from the true average density (also often called "bulk" density) because compression within planet cores increases their density; the average density depends on planet size, temperature distribution, and material stiffness as well as composition. Calculations to estimate uncompressed density inherently require

1680-510: A voyage into Neptune's atmosphere and Alex Irvine 's 2003 short story " Shepherded by Galatea " features resource extraction in the atmosphere. In the 1969 novel Macroscope by Piers Anthony , Neptune is converted to a world ship , and in the 1997 film Event Horizon the titular spacecraft is adrift in Neptunian orbit. The planet also appears in Jack Williamson 's 1985 short story " At

1785-457: A year before the planet's subsequent discoverer, Johann Gottfried Galle , and on two occasions, 4 and 12 August 1845. However, his out-of-date star maps and poor observing techniques meant that he failed to recognize the observations as such until he carried out later analysis. Challis was full of remorse but blamed his neglect on his maps and the fact that he was distracted by his concurrent work on comet observations. Meanwhile, Le Verrier sent

1890-433: Is Samuel R. Delany 's 1976 novel Triton ( a.k.a. Trouble on Triton: An Ambiguous Heterotopia ) which depicts future societies living there. Gordon Eklund 's 1989 novel A Thunder on Neptune is partially set on Triton and features an exobiological expedition to Neptune. In the 1994 novel Neptune Crossing by Jeffrey Carver , an alien on Triton helps humanity avert an impact event . Neptune Neptune

1995-432: Is 10–100 times greater than at the poles. This is interpreted as evidence for upwelling at the equator and subsidence near the poles, as photochemistry cannot account for the distribution without meridional circulation. In 2007, it was discovered that the upper troposphere of Neptune's south pole was about 10 K warmer than the rest of its atmosphere, which averages about 73 K (−200 °C). The temperature differential

2100-422: Is 28.32°, which is similar to the tilts of Earth (23°) and Mars (25°). As a result, Neptune experiences seasonal changes similar to those on Earth. The long orbital period of Neptune means that the seasons last for forty Earth years. Its sidereal rotation period (day) is roughly 16.11 hours. Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year

2205-434: Is 29.81 AU, and the aphelion distance is 30.33 AU. Neptune's orbital eccentricity is only 0.008678, making it the planet in the Solar System with the second most circular orbit after Venus . The orbit of Neptune is inclined 1.77° compared to that of Earth. On 11 July 2011, Neptune completed its first full barycentric orbit since its discovery in 1846; it did not appear at its exact discovery position in

SECTION 20

#1732845626562

2310-581: Is also possible for some others (e.g. Ceres, Mimas , Dione , Miranda , Ariel , Triton, and Pluto). Titan even has surface bodies of liquid, albeit liquid methane rather than water. Jupiter's Ganymede, though icy, does have a metallic core like the Moon, Io, Europa, and the terrestrial planets. The name Terran world has been suggested to define all solid worlds (bodies assuming a rounded shape), without regard to their composition. It would thus include both terrestrial and icy planets. The uncompressed density of

2415-518: Is banded by clouds of varying compositions depending on altitude. The upper-level clouds lie at pressures below one bar, where the temperature is suitable for methane to condense. For pressures between one and five bars (100 and 500 kPa), clouds of ammonia and hydrogen sulfide are thought 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 (5.0 MPa), where

2520-507: Is commonly used. In Māori , the planet is called Tangaroa , named after the Māori god of the sea . In Nahuatl , the planet is called Tlāloccītlalli , named after the rain god Tlāloc . In Thai , Neptune is referred to by the Westernised name Dao Nepchun/Nepjun ( ดาวเนปจูน ) but is also called Dao Ket ( ดาวเกตุ , lit.   ' star of Ketu ' ), after Ketu ( केतु ),

2625-466: Is enough to let methane, which elsewhere is frozen in the troposphere, escape into the stratosphere near the pole. The relative "hot spot" is due to Neptune's axial tilt , which has exposed the south pole to the Sun for the last quarter of Neptune's year, or roughly 40 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

2730-426: Is faintly blue in the optical spectrum , only slightly more saturated than the blue of Uranus's atmosphere. Early renderings of the two planets greatly exaggerated Neptune's colour contrast "to better reveal the clouds, bands and winds", making it seem deep blue compared to Uranus's off-white. The two planets had been imaged with different systems, making it hard to directly compare the resulting composite images . This

2835-445: Is favoured due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. The current most widely accepted explanation of the details of this hypothesis is known as the Nice model , which is a dynamical evolution scenario that explores the potential effect of a migrating Neptune and the other giant planets on the structure of

2940-512: Is harder to explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets. The average distance between Neptune and the Sun is 4.5 billion km (about 30.1  astronomical units (AU), the mean distance from the Earth to the Sun), and it completes an orbit on average every 164.79 years, subject to a variability of around ±0.1 years. The perihelion distance

3045-865: Is in the 1930 novel Last and First Men by Olaf Stapledon , which outlines the future history of humanity through several billions of years and various sequential species from the First Men to the Eighteenth. In the story, Neptune becomes humanity's refuge in the far future when the Sun expands. This plot point would later reappear in the 1934 short story " Twilight " by John W. Campbell and its 1935 sequel " Night ". After this however, says Stableford, Neptune "retreated into obscurity again as pulp science fiction grew more sophisticated". [ Gardner Dozois ] didn't mind that there were elephants on Neptune, or that they breathed oxygen, or that they could speak English, or that they could forage and find food—but it bothered

3150-409: Is likely composed of iron, nickel and silicates , with an interior model giving a mass about 1.2x that of Earth. The pressure at the centre is 7  Mbar (700 GPa), about twice as high as that at the centre of Earth, and the temperature may be 5,400 K (5,100 °C; 9,300 °F). At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium . A trace amount of methane

3255-558: Is nearly four times that of Earth . Neptune, like Uranus , is an ice giant , a subclass of giant planet , because they are smaller and have higher concentrations of volatiles than Jupiter and Saturn. In the search for exoplanets , Neptune has been used as a metonym : discovered bodies of similar mass are often referred to as "Neptunes", just as scientists refer to various extrasolar bodies as "Jupiters". Neptune's internal structure resembles that of Uranus . Its atmosphere forms about 5 to 10% of its mass and extends perhaps 10 to 20% of

Neptune in fiction - Misplaced Pages Continue

3360-426: 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

3465-407: Is present. Prominent absorption bands of methane exist at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by atmospheric methane is part of what gives Neptune its faint blue hue, which is more pronounced for Neptune's due to concentrated haze in Uranus's atmosphere. Neptune's atmosphere is subdivided into two main regions:

3570-471: Is that the ice giants were not formed 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 . An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. This hypothesis of migration after formation

3675-484: Is the eighth and farthest known planet from the Sun . 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 times the mass of Earth . Compared to its fellow ice giant Uranus , Neptune is slightly more massive, but denser and smaller. Being composed primarily of gases and liquids, it has no well-defined solid surface, and orbits

3780-690: Is thought to be a " skin effect " and not due to any deeper atmospheric processes. At 70°S latitude, a high-speed jet travels at a speed of 300 m/s. Due to 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. The long orbital period of Neptune results in seasons lasting 40 Earth years. Neptune differs from Uranus in its typical level of meteorological activity. Voyager 2 observed weather phenomena on Neptune during its 1989 flyby, but no comparable phenomena on Uranus during its 1986 flyby. The abundance of methane, ethane and acetylene at Neptune's equator

3885-733: Is unknown whether extrasolar terrestrial planets in general will follow such a trend. The data in the tables below are mostly taken from a list of gravitationally rounded objects of the Solar System and planetary-mass moon . All distances from the Sun are averages. Most of the planets discovered outside the Solar System are giant planets, because they are more easily detectable. But since 2005, hundreds of potentially terrestrial extrasolar planets have also been found, with several being confirmed as terrestrial. Most of these are super-Earths , i.e. planets with masses between Earth's and Neptune's; super-Earths may be gas planets or terrestrial, depending on their mass and other parameters. During

3990-675: The Milky Way galaxy . The following exoplanets have a density of at least 5 g/cm and a mass below Neptune's and are thus very likely terrestrial: Kepler-10b , Kepler-20b , Kepler-36b , Kepler-48d , Kepler 68c , Kepler-78b , Kepler-89b , Kepler-93b , Kepler-97b , Kepler-99b , Kepler-100b , Kepler-101c , Kepler-102b , Kepler-102d , Kepler-113b , Kepler-131b , Kepler-131c , Kepler-138c , Kepler-406b , Kepler-406c , Kepler-409b . In 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth- and super-Earth-sized planets orbiting in

4095-520: The Solar System have the same basic structure, such as a central metallic core (mostly iron ) with a surrounding silicate mantle . The large rocky asteroid 4 Vesta has a similar structure; possibly so does the smaller one 21 Lutetia . Another rocky asteroid 2 Pallas is about the same size as Vesta, but is significantly less dense; it appears to have never differentiated a core and a mantle. The Earth's Moon and Jupiter's moon Io have similar structures to terrestrial planets, but Earth's Moon has

4200-588: The dipole moment in strength. By contrast, Earth, Jupiter and Saturn have only 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 an offset from the planet's centre and geometrical constraints of the field's dynamo generator. Measurements by Voyager 2 in extreme-ultraviolet and radio frequencies revealed that Neptune has faint and weak but complex and unique aurorae ; however, these observations were limited in time and did not contain infrared. Subsequent astronomers using

4305-607: The habitable zones of Sun-like stars and red dwarfs within the Milky Way . Eleven billion of these estimated planets may be orbiting Sun-like stars. The nearest such planet may be 12 light-years away, according to the scientists. However, this does not give estimates for the number of extrasolar terrestrial planets, because there are planets as small as Earth that have been shown to be gas planets (see Kepler-138d ). Estimates show that about 80% of potentially habitable worlds are covered by land, and about 20% are ocean planets. Planets with rations more like those of Earth, which

Neptune in fiction - Misplaced Pages Continue

4410-596: The orbit of Uranus . 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 began work on the orbit of Uranus using the data he had. He requested extra data from Sir George Airy , the Astronomer Royal , who supplied it in February 1844. Adams continued to work in 1845–1846 and produced several different estimates of

4515-484: The outer , giant planets , whose atmospheres are primary; primary atmospheres were captured directly from the original solar nebula . The Solar System has four terrestrial planets under the dynamical definition: Mercury , Venus , Earth and Mars . The Earth's Moon as well as Jupiter's moons Io and Europa would also count geophysically, as well as perhaps the large protoplanet-asteroids Pallas and Vesta (though those are borderline cases). Among these bodies, only

4620-589: The transit method. In the same year, the Kepler space telescope mission team released a list of 1235 extrasolar planet candidates , including six that are "Earth-size" or "super-Earth-size" (i.e. they have a radius less than twice that of the Earth) and in the habitable zone of their star. Since then, Kepler has discovered hundreds of planets ranging from Moon-sized to super-Earths, with many more candidates in this size range (see image). In 2016, statistical modeling of

4725-568: The tropopause layer. The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other, unknown mechanism. In 1989, Voyager 2 's Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7 × 10   J . A plasma wave system (PWS) detected 16 electromagnetic wave events with

4830-448: The 1930 short story " The Monsters of Neptune " by Henrik Dahl Juve , this time with a tropical climate. Alien life on Neptune, while uncommon, appears in some stories; "A Baby on Neptune" features gaseous lifeforms and "The Monsters of Neptune" grotesque creatures, while Neptune in the 1932 novel The Vanguard to Neptune by J. M. Walsh is populated by humanoids . In the 1930 short story " The Universe Wreckers " by Edmond Hamilton ,

4935-403: The Earth has an active surface hydrosphere . Europa is believed to have an active hydrosphere under its ice layer. During the formation of the Solar System, there were many terrestrial planetesimals and proto-planets , but most merged with or were ejected by the four terrestrial planets, leaving only Pallas and Vesta to survive more or less intact. These two were likely both dwarf planets in

5040-457: The French Bureau des Longitudes . In October, he sought to name the planet Le Verrier , after himself, and he had loyal support in this from the observatory director, François Arago . This suggestion met with stiff resistance outside France. French almanacs quickly reintroduced the name Herschel for Uranus, after that planet's discoverer Sir  William Herschel , and Leverrier for

5145-620: The French and the British over who deserved credit for the discovery. Eventually, an international consensus emerged that Le Verrier and Adams deserved joint credit. Since 1966, Dennis Rawlins has questioned the credibility of Adams's claim to co-discovery, and the issue was re-evaluated by historians with the return in 1998 of the "Neptune papers" (historical documents) to the Royal Observatory, Greenwich . Shortly after its discovery, Neptune

5250-486: The Hubble Space Telescope have not glimpsed the aurorae, in contrast to the more well-defined aurorae of Uranus. 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

5355-561: The Human Limit ", Gregory Feeley 's 1986 short story " Neptune's Reach ", the adventures of comic book superhero Superman , the television series Doctor Who , and the video game Descent . Neptune's largest moon Triton was discovered less than a month after the planet. A few works in the 1930s depicted humans going to Triton, looking for minerals in Roman Frederick Starzl 's 1932 short story " The Power Satellite " and

SECTION 50

#1732845626562

5460-496: The Kuiper belt. 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. Much in the same way that Jupiter's gravity dominates the asteroid belt , Neptune's gravity dominates

5565-410: The Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in its structure. The region between 40 and 42 AU is an example. There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune's orbital period is a precise fraction of that of

5670-446: The Solar System, and it results in strong latitudinal wind shear. The formation of the ice giants, Neptune and Uranus, has been 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 formation. One

5775-593: The Sun once every 164.8  years at an orbital distance of 30.1 astronomical units (4.5 billion kilometres; 2.8 billion miles). It is named after the Roman god of the sea and has the astronomical symbol [REDACTED] , representing Neptune's trident . Neptune is not visible to the unaided eye and is the only planet in the Solar System that was found from mathematical predictions derived from indirect observations rather than being initially observed by direct empirical observation , when unexpected changes in

5880-413: The Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55  K (−218  °C ; −361  °F ). Temperatures at the planet's centre are approximately 5,400 K (5,100 °C; 9,300 °F). Neptune has a faint and fragmented ring system (labelled "arcs"), discovered in 1984 and confirmed by Voyager 2 . Some of

5985-485: The Sun, making Neptune the ninth planet from the Sun during this period. The increasingly accurate estimations of Pluto's mass from ten times that of Earth's to far less than that of the Moon and the discovery of the Kuiper belt in 1992 led many astronomers to debate whether Pluto should be considered a planet or as part of the Kuiper belt. In 2006, the International Astronomical Union defined

6090-464: The Sun; whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. Neptune is over 50% farther from the Sun than Uranus and receives only ~40% of Uranus's amount of sunlight; however, its internal energy is still enough for the fastest planetary winds in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it

6195-555: The advent of the Hubble Space Telescope and of large ground-based telescopes with adaptive optics allowed for detailed observations. Neptune was visited by Voyager 2 , which flew by the planet on 25 August 1989; Voyager 2 remains the only spacecraft to have visited it. Like the gas giants ( Jupiter and Saturn ), Neptune's atmosphere is composed primarily of hydrogen and helium , along with traces of hydrocarbons and possibly nitrogen , but contains

6300-502: The catalog of known exoplanets has increased significantly, and there have been several published refinements of the mass-radius model. As of 2024, the expected transition point between rocky and intermediate-mass planets sits at roughly 4.4 earth masses, and roughly 1.6 earth radii. In September 2020, astronomers using microlensing techniques reported the detection , for the first time, of an Earth-mass rogue planet (named OGLE-2016-BLG-1928 ) unbounded by any star, and free-floating in

6405-431: The cloud deck. These altitudes are in the layer where weather occurs, the troposphere. Weather does not occur in the higher stratosphere or thermosphere. In August 2023, the high-altitude clouds of Neptune vanished, prompting a study spanning thirty years of observations by the Hubble Space Telescope and ground-based telescopes. The study found that Neptune's high-altitude cloud activity is bound to Solar cycles , and not to

SECTION 60

#1732845626562

6510-411: The day Galle received the letter, he discovered Neptune just northeast of Iota Aquarii , 1° from the " five degrees east of Delta Capricorn " position Le Verrier had predicted it to be, about 12° from Adams's prediction, and on the border of Aquarius and Capricornus according to the modern IAU constellation boundaries. In the wake of the discovery, there was a nationalistic rivalry between

6615-653: The descending lunar node , who plays a role in Hindu astrology . In Malay , the name Waruna , after the Hindu god of seas , is attested as far back as the 1970s, but was eventually superseded by the Latinate equivalents Neptun (in Malaysian ) or Neptunus (in Indonesian ). The usual adjectival form is Neptunian . The nonce form Poseidean ( / p ə ˈ s aɪ d i ən / ), from Poseidon , has also been used, though

6720-475: The distance from the Sun increases, consistent with the temperature gradient that would have existed within the primordial solar nebula. The Galilean satellites show a similar trend going outwards from Jupiter; however, no such trend is observable for the icy satellites of Saturn or Uranus. The icy worlds typically have densities less than 2 g·cm . Eris is significantly denser ( 2.43 ± 0.05 g·cm ), and may be mostly rocky with some surface ice, like Europa. It

6825-509: The earliest known telescopic observations ever, Galileo's drawings on 28 Dec. 1612 and 27 Jan. 1613 ( New Style ) contain plotted points that match what is now known to have been the positions of Neptune on those dates. Both times, Galileo seems to have mistaken Neptune for a fixed star when it appeared close—in conjunction —to Jupiter in the night sky . Hence, he is not credited with Neptune's discovery. At his first observation in Dec. 1612, Neptune

6930-453: The early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12 , with masses of 0.02, 4.3, and 3.9 times that of Earth, by pulsar timing . When 51 Pegasi b , the first planet found around a star still undergoing fusion , was discovered, many astronomers assumed it to be a gigantic terrestrial, because it was assumed no gas giant could exist as close to its star (0.052 AU) as 51 Pegasi b did. It

7035-402: The easterly direction to 325 m/s westward. At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles. Most of the winds on Neptune move in a direction opposite the planet's rotation. The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction

7140-915: The exceptions have ranged from humanoids to gaseous lifeforms. Neptune's largest moon Triton has also appeared in fiction, especially in the late 20th century onwards. Neptune was discovered in 1846 and has only made occasional appearances in fiction since then; in the catalogue of early science fiction works compiled by E. F. Bleiler and Richard Bleiler in the reference works Science-Fiction: The Early Years from 1990 and Science-Fiction: The Gernsback Years from 1998, Neptune appears in 9 (out of 2,475) and 18 (out of 1,835) works respectively, compared to 194 for Mars in fiction and 131 for Venus in fiction in The Gernsback Years alone. Brian Ash writes in The Visual Encyclopedia of Science Fiction that "Neptune has been largely overlooked in

7245-445: The first ground-based observation of a dark spot on Neptune was announced. Neptune's dark spots are thought to occur in the troposphere at lower altitudes than the brighter cloud features, 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. Often associated with dark spots are brighter, persistent methane clouds that form around

7350-400: The forces of a rival empire centered on Sirius . Early works incorrectly depicted Neptune as a solid planet , and several stories thus include human expeditions to its surface. The earliest story where Neptune itself directly appears as a setting is the 1929 short story " A Baby on Neptune " by Clare Winger Harris and Miles J. Breuer , where the planet is covered in ice. It also appears in

7455-475: The former inhabitants of Neptune have left the planet for its moon Triton due to environmental changes . The concept of Neptune turning into a star from "The Star" was reused in the 1932 short story " Raiders of the Universes " by Donald Wandrei , although in this case it then proceeds to leave the Solar System rather than heading towards its center. The most significant appearance of Neptune in fiction in this era

7560-692: The genre", and Richard L. McKinney describes it as "unexplored territory" in The Greenwood Encyclopedia of Science Fiction and Fantasy . The Encyclopedia of Science Fiction attributes this in part to its relatively late date of discovery, Brian Stableford writes in Science Fact and Science Fiction: An Encyclopedia that its remote location was a significant factor, and science fiction scholar Gary Westfahl posits in Science Fiction Literature through History: An Encyclopedia that

7665-475: The habitable zone of the star, so they could potentially be habitable, with Earth-like temperatures. Another possibly terrestrial planet, HD 85512 b , was discovered in 2011; it has at least 3.6 times the mass of Earth. The radius and composition of all these planets are unknown. The first confirmed terrestrial exoplanet , Kepler-10b , was found in 2011 by the Kepler space telescope , specifically designed to discover Earth-size planets around other stars using

7770-542: The hell out of him that I'd given Neptune a solid surface when everyone knows it's a gas giant, so I had to insert a sentence explaining that. Mike Resnick , on selling the 2002 short story " The Elephants on Neptune " to Asimov's Science Fiction Once more became known about Neptune through advances in planetary science , fiction writers began portraying it more accurately as a gaseous planet . Thus Alexei Panshin 's 1969 short story " One Sunday in Neptune " depicts

7875-534: The largest of the known Kuiper belt objects, Pluto , is among them. Although Pluto crosses Neptune's orbit regularly, the 2:3 resonance makes it so that they can never collide. The 3:4, 3:5, 4:7 and 2:5 resonances are less populated. Rocky planet Terrestrial planets have a solid planetary surface , making them substantially different from larger gaseous planets , which are composed mostly of some combination of hydrogen , helium , and water existing in various physical states . All terrestrial planets in

7980-453: The lower troposphere , where temperature decreases with altitude, and the stratosphere , where temperature increases with altitude. The boundary between the two, the tropopause , lies at a pressure of 0.1 bars (10 kPa). The stratosphere then gives way to the thermosphere at a pressure lower than 10 to 10  bars (1 to 10 Pa). The thermosphere gradually transitions to the exosphere . Models suggest that Neptune's troposphere

8085-405: The magnetic equator of Neptune is about 14  microteslas (0.14  G ). The dipole magnetic moment of Neptune is about 2.2 × 10  T·m (14 μT· R N , where R N is the radius of Neptune). 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

8190-401: 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), resulting in a dynamo action. The dipole component of the magnetic field at

8295-403: The magnetosphere extends out to at least 72 times the radius of Neptune, and likely much farther. Neptune's weather is characterized by extremely dynamic storm systems, with winds reaching speeds of almost 600 m/s (2,200 km/h; 1,300 mph)—exceeding supersonic flow. More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in

8400-492: The mass of Earth and orbits a star about 21,000 light-years away in the constellation Scorpius. From 2007 to 2010, three (possibly four) potential terrestrial planets were found orbiting within the Gliese 581 planetary system . The smallest, Gliese 581e , is only about 1.9 Earth masses, but orbits very close to the star. Two others, Gliese 581c and the disputed Gliese 581d , are more-massive super-Earths orbiting in or close to

8505-579: The methane release to shift to the north pole. In 1989, the Great Dark Spot , an anticyclonic storm system spanning 13,000 km × 6,600 km (8,100 mi × 4,100 mi), was discovered by NASA 's Voyager 2 spacecraft. The storm resembled the Great Red Spot of Jupiter. Some five years later, on 2 November 1994, the Hubble Space Telescope did not see the Great Dark Spot on

8610-544: The new planet. Struve came out in favour of the name Neptune on 29 December 1846, to the Saint Petersburg Academy of Sciences , after the colour of the planet as viewed through a telescope. 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

8715-448: The nomenclature of the other planets, all of which were named for deities in Greek and Roman mythology. Most languages today use some variant of the name "Neptune" for the planet. In Chinese, Vietnamese, Japanese, and Korean, the planet's name was translated as "sea king star" ( 海王星 ). In Mongolian , Neptune is called Dalain van ( Далайн ван ), reflecting its namesake god's role as

8820-404: The object, 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 by the time Neptune returns to its original position. The most heavily populated resonance in the Kuiper belt, with over 200 known objects, is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because

8925-404: The orbit of Uranus led Alexis Bouvard to hypothesise that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard's death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier . Neptune was subsequently directly observed with a telescope on 23 September 1846 by Johann Gottfried Galle within

9030-464: The past, but have been battered out of equilibrium shapes by impacts. Some other protoplanets began to accrete and differentiate but suffered catastrophic collisions that left only a metallic or rocky core, like 16 Psyche or 8 Flora respectively. Many S-type and M-type asteroids may be such fragments. The other round bodies from the asteroid belt outward are geophysically icy planets . They are similar to terrestrial planets in that they have

9135-505: The planet visits Earth. Neptune was usually omitted in the subgenre of works visiting multiple locations in the Solar System that appeared in this time, though it did make some indirect appearances in works not otherwise set there. Supernatural communication with its inhabitants appears in Marie Corelli 's 1892 novel The Soul of Lilith . In the 1897 short story " The Star " by H. G. Wells , an impact event causes Neptune to turn into

9240-429: The planet's seasons. Neptune's spectra suggest that its lower stratosphere is hazy due to condensation of products of ultraviolet photolysis of methane, such as ethane and ethyne . The stratosphere is home to trace amounts of carbon monoxide and hydrogen cyanide . The stratosphere of Neptune is warmer than that of Uranus due to the elevated concentration of hydrocarbons. For reasons that remain obscure,

9345-576: The planet's thermosphere is at an anomalously high temperature of about 750 K (477 °C; 890 °F). 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. Neptune's atmosphere

9450-472: The planet. Instead, a new storm similar to the Great Dark Spot was found in Neptune's northern hemisphere. The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when they were observed moving at speeds faster than the Great Dark Spot (and images acquired later would subsequently reveal

9555-476: The presence of clouds moving even faster than those that had initially been detected by Voyager 2 ). The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It was initially completely dark, but as Voyager 2 approached the planet, a bright core developed, which can be seen in most of the highest-resolution images. In 2018, a newer main dark spot and smaller dark spot were identified and studied. In 2023,

9660-399: The presumed-harsh environmental conditions of the planet made it unappealing for writers to use it as a setting . The first time Neptune was mentioned in a work of fiction—then called "Leverrier's planet" after astronomer Urbain Le Verrier whose orbital calculations led to the planet's discovery —was in the 1848 novel The Triumphs of Woman by Charles Rowcroft where an inhabitant of

9765-450: The relationship between a planet's mass and radius using a broken power law appeared to suggest that the transition point between rocky, terrestrial worlds and mini-Neptunes without a defined surface was in fact very close to Earth and Venus's, suggesting that rocky worlds much larger than our own are in fact quite rare. This resulted in some advocating for the retirement of the term "super-earth" as being scientifically misleading. Since 2016

9870-618: The ruler of the sea. In modern Greek , the planet is called Poseidon ( Ποσειδώνας , Poseidonas ), the Greek counterpart of Neptune. In Hebrew , Rahab ( רהב ), from a Biblical sea monster mentioned in the Book of Psalms , was selected in a vote managed by the Academy of the Hebrew Language in 2009 as the official name for the planet, even though the existing Latin term Neptun ( נפטון )

9975-448: The sky because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July, Neptune was not at its exact discovery position in relation to the Sun—if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011. The axial tilt of Neptune

10080-406: The temperature reaches 273 K (0 °C; 32 °F). Underneath, clouds of ammonia and hydrogen sulfide may be found. High-altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are high-altitude cloud bands that wrap around the planet at constant latitudes. These circumferential bands have widths of 50–150 km and lie about 50–110 km above

10185-486: The time of the Voyager ;2 flyby in 1989, the planet's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. In 2018, a newer main dark spot and smaller dark spot were identified and studied. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, as high as 2,100 km/h (580 m/s; 1,300 mph). Because of its great distance from

10290-442: The usual adjectival form of Poseidon is Poseidonian ( / ˌ p ɒ s aɪ ˈ d oʊ n i ən / ). From its discovery in 1846 until the discovery of Pluto in 1930, Neptune was the farthest known planet. When Pluto was discovered, it was considered a planet, and Neptune thus became the second-farthest known planet, except for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer than Neptune to

10395-476: The water clouds of the troposphere or the shallow ammonia clouds of the magnetosphere. Neptune is predicted to have 1/19 the lightning flash rate of Jupiter and to display most of its lightning activity at high latitudes. However, lightning on Neptune seems to resemble lightning on Earth rather than Jovian lightning. Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating . The upper regions of Neptune's troposphere reach

10500-399: The way towards the core. Pressure in the atmosphere reaches about 10  GPa , or about 10 atmospheres. Increasing concentrations of methane , ammonia and water are found in the lower regions of the atmosphere. The mantle is equivalent to 10 to 15 Earth masses and is rich in water, ammonia and methane. As is customary in planetary science, this mixture is called icy even though it is

10605-492: The word "planet" for the first time, reclassifying Pluto as a " dwarf planet " and making Neptune once again the outermost-known planet in the Solar System. Neptune's mass of 1.0243 × 10  kg is intermediate between Earth and the larger gas giants : it is 17 times that of Earth but just 1/19th that of Jupiter . Its gravity at 1 bar is 11.15 m/s , 1.14 times the surface gravity of Earth, and surpassed only by Jupiter. Neptune's equatorial radius of 24,764 km

10710-517: Was almost stationary in the sky because it had just turned retrograde that day. This apparent backward motion is created when Earth's orbit takes it past an outer planet. Because 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. In 2009, a study suggested that Galileo was at least aware that the "star" he had observed had moved relative to fixed stars. In 1821, Alexis Bouvard published astronomical tables of

10815-426: Was later found to be a gas giant. In 2005, the first planets orbiting a main-sequence star and which showed signs of being terrestrial planets were found: Gliese 876 d and OGLE-2005-BLG-390Lb . Gliese 876 d orbits the red dwarf Gliese 876 , 15 light years from Earth, and has a mass seven to nine times that of Earth and an orbital period of just two Earth days. OGLE-2005-BLG-390Lb has about 5.5 times

10920-410: 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 forward the name Oceanus . Claiming the right to name his discovery, Le Verrier quickly proposed the name Neptune for this new planet, though falsely stating that this had been officially approved by

11025-483: Was revisited with the colour normalised over time, most comprehensively in late 2023. Neptune's magnetosphere consists of a magnetic field that is strongly tilted relative to its rotational axis at 47° and offset of at least 0.55 radius (~13,500 km) from the planet's physical centre—resembling Uranus's magnetosphere. Before the arrival of Voyager 2 to Neptune, it was hypothesised that Uranus's sideways rotation caused its tilted magnetosphere. In comparing

#561438