110-559: Neptune is the eighth and farthest planet from the Sun. Neptune may also refer to: Neptune Neptune 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
220-405: A body B at the temperature ( T − 1)° , would give out the same mechanical effect, whatever be the number T ." Specifically, Thomson expressed the amount of work necessary to produce a unit of heat (the thermal efficiency ) as μ ( t ) ( 1 + E t ) / E {\displaystyle \mu (t)(1+Et)/E} , where t {\displaystyle t}
330-510: A committee of the CGPM, affirmed that for the purposes of delineating the temperature of the triple point of water, the definition of the kelvin would refer to water having the isotopic composition specified for Vienna Standard Mean Ocean Water . In 2005, the CIPM began a programme to redefine the kelvin (along with other SI base units ) using a more experimentally rigorous method. In particular,
440-431: 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
550-606: 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
660-433: A gas cooled to about −273 °C would occupy zero volume. In 1848, William Thomson, who was later ennobled as Lord Kelvin , published a paper On an Absolute Thermometric Scale . The scale proposed in the paper turned out to be unsatisfactory, but the principles and formulas upon which the scale was based were correct. For example, in a footnote, Thomson derived the value of −273 °C for absolute zero by calculating
770-497: A given substance can occur only at a single pressure and only at a single temperature. By the 1940s, the triple point of water had been experimentally measured to be about 0.6% of standard atmospheric pressure and very close to 0.01 °C per the historical definition of Celsius then in use. In 1948, the Celsius scale was recalibrated by assigning the triple point temperature of water the value of 0.01 °C exactly and allowing
880-410: 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
990-485: 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,
1100-401: 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
1210-514: 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
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#17327718302521320-528: 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 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
1430-537: A relative standard uncertainty of 3.7 × 10 . Afterward, the Boltzmann constant is exact and the uncertainty is transferred to the triple point of water, which is now 273.1600(1) K . The new definition officially came into force on 20 May 2019, the 144th anniversary of the Metre Convention . The kelvin is often used as a measure of the colour temperature of light sources. Colour temperature
1540-412: A starting point, with Celsius being defined (from the 1740s to the 1940s ) by calibrating a thermometer such that: This definition assumes pure water at a specific pressure chosen to approximate the natural air pressure at sea level. Thus, an increment of 1 °C equals 1 / 100 of the temperature difference between the melting and boiling points. The same temperature interval
1650-457: 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
1760-481: Is "the mechanical equivalent of a unit of heat", now referred to as the specific heat capacity of water, approximately 771.8 foot-pounds force per degree Fahrenheit per pound (4,153 J/K/kg). Thomson was initially skeptical of the deviations of Joule's formula from experiment, stating "I think it will be generally admitted that there can be no such inaccuracy in Regnault's part of the data, and there remains only
1870-432: 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
1980-422: 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
2090-434: 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
2200-521: Is a type of thermal noise derived from the Boltzmann constant and can be used to determine the noise temperature of a circuit using the Friis formulas for noise . The only SI derived unit with a special name derived from the kelvin is the degree Celsius. Like other SI units, the kelvin can also be modified by adding a metric prefix that multiplies it by a power of 10 : According to SI convention,
2310-518: 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
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#17327718302522420-399: Is based upon the principle that a black body radiator emits light with a frequency distribution characteristic of its temperature. Black bodies at temperatures below about 4000 K appear reddish, whereas those above about 7500 K appear bluish. Colour temperature is important in the fields of image projection and photography, where a colour temperature of approximately 5600 K
2530-764: Is common convention to capitalize Kelvin when referring to Lord Kelvin or the Kelvin scale. The unit symbol K is encoded in Unicode at code point U+212A K KELVIN SIGN . However, this is a compatibility character provided for compatibility with legacy encodings. The Unicode standard recommends using U+004B K LATIN CAPITAL LETTER K instead; that is, a normal capital K . "Three letterlike symbols have been given canonical equivalence to regular letters: U+2126 Ω OHM SIGN , U+212A K KELVIN SIGN , and U+212B Å ANGSTROM SIGN . In all three instances,
2640-513: 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 ),
2750-421: 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
2860-426: 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
2970-449: 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
3080-571: 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
3190-427: Is in allowing more accurate measurements at very low and very high temperatures, as the techniques used depend on the Boltzmann constant. Independence from any particular substance or measurement is also a philosophical advantage. The kelvin now only depends on the Boltzmann constant and universal constants (see 2019 SI unit dependencies diagram), allowing the kelvin to be expressed exactly as: For practical purposes,
3300-409: 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
3410-558: 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 (disambiguation) - Misplaced Pages Continue
3520-426: 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
3630-415: 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 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,
3740-407: 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:
3850-555: Is proportional to μ {\displaystyle \mu } . When Thomson published his paper in 1848, he only considered Regnault's experimental measurements of μ ( t ) {\displaystyle \mu (t)} . That same year, James Prescott Joule suggested to Thomson that the true formula for Carnot's function was μ ( t ) = J E 1 + E t , {\displaystyle \mu (t)=J{\frac {E}{1+Et}},} where J {\displaystyle J}
3960-572: Is required to match "daylight" film emulsions. In astronomy , the stellar classification of stars and their place on the Hertzsprung–Russell diagram are based, in part, upon their surface temperature, known as effective temperature . The photosphere of the Sun , for instance, has an effective temperature of 5772 K [1] [2] [3] [4] as adopted by IAU 2015 Resolution B3. Digital cameras and photographic software often use colour temperature in K in edit and setup menus. The simple guide
4070-488: Is slightly more massive, but denser and smaller. Being composed primarily of gases and liquids, it has no well-defined solid surface, and orbits 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
4180-463: Is that higher colour temperature produces an image with enhanced white and blue hues. The reduction in colour temperature produces an image more dominated by reddish, "warmer" colours . For electronics , the kelvin is used as an indicator of how noisy a circuit is in relation to an ultimate noise floor , i.e. the noise temperature . The Johnson–Nyquist noise of resistors (which produces an associated kTC noise when combined with capacitors )
4290-471: 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
4400-652: Is the temperature in Celsius, E {\displaystyle E} is the coefficient of thermal expansion, and μ ( t ) {\displaystyle \mu (t)} was "Carnot's function", a substance-independent quantity depending on temperature, motivated by an obsolete version of Carnot's theorem . The scale is derived by finding a change of variables T 1848 = f ( T ) {\displaystyle T_{1848}=f(T)} of temperature T {\displaystyle T} such that d T 1848 / d T {\displaystyle dT_{1848}/dT}
4510-690: 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
Neptune (disambiguation) - Misplaced Pages Continue
4620-442: The Boltzmann constant to exactly 1.380 649 × 10 joules per kelvin; every 1 K change of thermodynamic temperature corresponds to a thermal energy change of exactly 1.380 649 × 10 J . During the 18th century, multiple temperature scales were developed, notably Fahrenheit and centigrade (later Celsius). These scales predated much of the modern science of thermodynamics , including atomic theory and
4730-588: 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
4840-399: The kinetic theory of gases which underpin the concept of absolute zero. Instead, they chose defining points within the range of human experience that could be reproduced easily and with reasonable accuracy, but lacked any deep significance in thermal physics. In the case of the Celsius scale (and the long since defunct Newton scale and Réaumur scale ) the melting point of ice served as such
4950-418: The melting point at standard atmospheric pressure to have an empirically determined value (and the actual melting point at ambient pressure to have a fluctuating value) close to 0 °C. This was justified on the grounds that the triple point was judged to give a more accurately reproducible reference temperature than the melting point. The triple point could be measured with ±0.0001 °C accuracy, while
5060-568: 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
5170-475: The 13th CGPM renamed the unit increment of thermodynamic temperature "kelvin", symbol K, replacing "degree Kelvin", symbol °K. The 13th CGPM also held in Resolution ;4 that "The kelvin, unit of thermodynamic temperature, is equal to the fraction 1 / 273.16 of the thermodynamic temperature of the triple point of water." After the 1983 redefinition of the metre , this left
5280-477: 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 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
5390-464: 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
5500-637: 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
5610-496: 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
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#17327718302525720-504: 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
5830-410: 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
5940-446: 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
6050-549: 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
6160-464: 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
6270-614: The absolute temperature as T H = J / μ {\displaystyle T_{H}=J/\mu } . One finds the relationship T H = J × Q H × ( t H − t C ) / W {\displaystyle T_{H}=J\times Q_{H}\times (t_{H}-t_{C})/W} . By supposing T H − T C = J × ( t H − t c ) {\displaystyle T_{H}-T_{C}=J\times (t_{H}-t_{c})} , one obtains
6380-431: 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
6490-401: The committee proposed redefining the kelvin such that the Boltzmann constant ( k B ) would take the exact value 1.380 6505 × 10 J/K . The committee hoped the program would be completed in time for its adoption by the CGPM at its 2011 meeting, but at the 2011 meeting the decision was postponed to the 2014 meeting when it would be considered part of a larger program . A challenge
6600-411: 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
6710-673: 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
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#17327718302526820-402: 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
6930-445: 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
7040-473: The general principle of an absolute thermodynamic temperature scale for the Carnot engine, Q H / T H = Q C / T C {\displaystyle Q_{H}/T_{H}=Q_{C}/T_{C}} . The definition can be shown to correspond to the thermometric temperature of the ideal gas laws . This definition by itself is not sufficient. Thomson specified that
7150-451: The kelvin is never referred to nor written as a degree . The word "kelvin" is not capitalized when used as a unit. It may be in plural form as appropriate (for example, "it is 283 kelvins outside", as for "it is 50 degrees Fahrenheit" and "10 degrees Celsius"). The unit's symbol K is a capital letter, per the SI convention to capitalize symbols of units derived from the name of a person. It
7260-514: The kelvin, the second, and the kilogram as the only SI units not defined with reference to any other unit. In 2005, noting that the triple point could be influenced by the isotopic ratio of the hydrogen and oxygen making up a water sample and that this was "now one of the major sources of the observed variability between different realizations of the water triple point", the International Committee for Weights and Measures (CIPM),
7370-554: 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. Kelvin The kelvin (symbol: K ) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at
7480-453: 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
7590-471: The lowest possible temperature ( absolute zero ), taken to be 0 K. By definition, the Celsius scale (symbol °C) and the Kelvin scale have the exact same magnitude; that is, a rise of 1 K is equal to a rise of 1 °C and vice versa, and any temperature in degrees Celsius can be converted to kelvin by adding 273.15. The 19th century British scientist Lord Kelvin first developed and proposed
7700-405: 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
7810-401: 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
7920-403: 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
8030-437: The melting point just to ±0.001 °C. In 1954, with absolute zero having been experimentally determined to be about −273.15 °C per the definition of °C then in use, Resolution 3 of the 10th General Conference on Weights and Measures (CGPM) introduced a new internationally standardized Kelvin scale which defined the triple point as exactly 273.15 + 0.01 = 273.16 degrees Kelvin. In 1967/1968, Resolution 3 of
8140-600: 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
8250-447: The modern Kelvin scale T {\displaystyle T} , the first scale could be expressed as follows: T 1848 = 100 × log ( T / 273 K ) log ( 373 K / 273 K ) {\displaystyle T_{1848}=100\times {\frac {\log(T/{\text{273 K}})}{\log({\text{373 K}}/{\text{273 K}})}}} The parameters of
8360-420: The negative reciprocal of 0.00366—the coefficient of thermal expansion of an ideal gas per degree Celsius relative to the ice point. This derived value agrees with the currently accepted value of −273.15 °C, allowing for the precision and uncertainty involved in the calculation. The scale was designed on the principle that "a unit of heat descending from a body A at the temperature T ° of this scale, to
8470-561: 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
8580-452: 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
8690-404: 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
8800-468: 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 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,
8910-566: 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 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
9020-399: 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 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
9130-429: 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,
9240-576: 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
9350-532: 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
9460-439: 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 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
9570-520: 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 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
9680-476: 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,
9790-431: The redefinition was unnoticed; enough digits were used for the Boltzmann constant to ensure that 273.16 K has enough significant digits to contain the uncertainty of water's triple point and water still normally freezes at 0 °C to a high degree of precision. But before the redefinition, the triple point of water was exact and the Boltzmann constant had a measured value of 1.380 649 03 (51) × 10 J/K , with
9900-400: The relationship between work and heat for a perfect thermodynamic engine was simply the constant J {\displaystyle J} . In 1854, Thomson and Joule thus formulated a second absolute scale that was more practical and convenient, agreeing with air thermometers for most purposes. Specifically, "the numerical measure of temperature shall be simply the mechanical equivalent of
10010-638: 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 )
10120-488: The scale should have two properties: These two properties would be featured in all future versions of the Kelvin scale, although it was not yet known by that name. In the early decades of the 20th century, the Kelvin scale was often called the "absolute Celsius " scale, indicating Celsius degrees counted from absolute zero rather than the freezing point of water, and using the same symbol for regular Celsius degrees, °C. In 1873, William Thomson's older brother James coined
10230-504: The scale were arbitrarily chosen to coincide with the Celsius scale at 0° and 100 °C or 273 and 373 K (the melting and boiling points of water). On this scale, an increase of approximately 222 degrees corresponds to a doubling of Kelvin temperature, regardless of the starting temperature, and "infinite cold" ( absolute zero ) has a numerical value of negative infinity . Thomson understood that with Joule's proposed formula for μ {\displaystyle \mu } ,
10340-495: The scale. It was often called the "absolute Celsius" scale in the early 20th century. The kelvin was formally added to the International System of Units in 1954, defining 273.16 K to be the triple point of water . The Celsius, Fahrenheit , and Rankine scales were redefined in terms of the Kelvin scale using this definition. The 2019 revision of the SI now defines the kelvin in terms of energy by setting
10450-448: 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
10560-571: The system ( Q H − Q C {\displaystyle Q_{H}-Q_{C}} ), t H {\displaystyle t_{H}} is the temperature of the hot reservoir in Celsius, and t C {\displaystyle t_{C}} is the temperature of the cold reservoir in Celsius. The Carnot function is defined as μ = W / Q H / ( t H − t C ) {\displaystyle \mu =W/Q_{H}/(t_{H}-t_{C})} , and
10670-522: 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
10780-406: 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
10890-428: The term triple point to describe the combination of temperature and pressure at which the solid, liquid, and gas phases of a substance were capable of coexisting in thermodynamic equilibrium . While any two phases could coexist along a range of temperature-pressure combinations (e.g. the boiling point of water can be affected quite dramatically by raising or lowering the pressure), the triple point condition for
11000-411: The thermal unit divided by Carnot's function." To explain this definition, consider a reversible Carnot cycle engine, where Q H {\displaystyle Q_{H}} is the amount of heat energy transferred into the system, Q C {\displaystyle Q_{C}} is the heat leaving the system, W {\displaystyle W} is the work done by
11110-466: The uncertainty regarding the density of saturated steam". Thomson referred to the correctness of Joule's formula as " Mayer 's hypothesis", on account of it having been first assumed by Mayer. Thomson arranged numerous experiments in coordination with Joule, eventually concluding by 1854 that Joule's formula was correct and the effect of temperature on the density of saturated steam accounted for all discrepancies with Regnault's data. Therefore, in terms of
11220-442: 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
11330-476: 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
11440-399: 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
11550-492: 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
11660-414: Was later used for the Kelvin scale. From 1787 to 1802, it was determined by Jacques Charles (unpublished), John Dalton , and Joseph Louis Gay-Lussac that, at constant pressure, ideal gases expanded or contracted their volume linearly ( Charles's law ) by about 1/273 parts per degree Celsius of temperature's change up or down, between 0 °C and 100 °C. Extrapolation of this law suggested that
11770-414: 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 the orbit of Uranus . Subsequent observations revealed substantial deviations from
11880-410: 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
11990-483: 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
12100-415: Was to avoid degrading the accuracy of measurements close to the triple point. The redefinition was further postponed in 2014, pending more accurate measurements of the Boltzmann constant in terms of the current definition, but was finally adopted at the 26th CGPM in late 2018, with a value of k B = 1.380 649 × 10 J⋅K . For scientific purposes, the redefinition's main advantage
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