Where is the planet Neptune. Planet Neptune
Neptune was discovered according to theoretical calculations. The fact is that Uranus deviates from the calculated orbit, as if it is attracted by another planet.
British mathematicians and astronomers John Couch Adams(1819-1892) and James Challis in 1845 calculated the approximate location of the planet. At the same time, the French astronomer Urban Le Verrier(1811 - 1877), having made a calculation, convinced him to start searching for a new planet. For the first time, astronomers saw Neptune on September 23, 1846, not far from the positions that the Englishman Adams and the Frenchman Le Verrier predicted independently of each other.
Neptune is far from the Sun.
General characteristics of the planet Neptune
The mass of the planet is 17 times the mass of the Earth. The radius of the planet is about four Earth radii. Density - Oz density of the Earth.
Rings have been discovered around Neptune. They are open (broken), i.e., they consist of separate arches that are not interconnected. The rings of Uranus and Neptune are similar in appearance.
The structure of Neptune is probably almost the same as Uranus.
Unlike with , and Neptune may not have a clear internal stratification. But, most likely, Neptune has a small solid core, equal in mass to the Earth. The atmosphere of Neptune is mostly hydrogen and helium with a small admixture of methane (1%). The blue color of Neptune is the result of absorption of red light in the atmosphere by this gas - just like on Uranus.
The planet has a thunderous atmosphere, thin porous clouds made of frozen methane. The temperature of the atmosphere of Neptune is higher than that of Uranus, therefore, about 80% H 2
Rice. 1. The composition of the atmosphere of Neptune
Neptune has its own internal heat source - it radiates 2.7 times more energy than it receives from the Sun. The average surface temperature of the planet is 235°C. On Neptune, there are strong winds parallel to the planet's equator, large storms and whirlwinds. The planet has the fastest winds in the solar system, reaching 700 km/h. Winds blow on Neptune westbound, against the rotation of the planet.
There are mountain ranges and cracks on the surface. Nitrogen snow falls in winter, and fountains break through the cracks in summer.
The Voyalger 2 probe discovered powerful cyclones on Neptune, in which the wind speed reaches the speed of sound.
The satellites of the planet are called Triton, Nereid, Naiad, Thalassa, Proteus, Despina, Galatea, Larissa. In 2002-2005 five more satellites of Neptune were discovered. Each of the newly discovered ones has a diameter of 30-60 km.
Most large satellite Neptune - Triton. It was opened in 1846 by William Lassell. Triton is larger than the Moon. Almost the entire mass of Neptune's satellite system is concentrated in Triton. It has a high density: 2 g / cm 3.
Neptune is the eighth planet from the Sun. In some places, its orbit intersects with the orbit of Pluto. What planet is Neptune? She belongs to the category of giants. Astrological sign- J.
Options
The giant planet Neptune moves around the Sun in an elliptical orbit close to circular. The length of the radius is 24,750 kilometers. This figure is four times greater than that of the Earth. The planet's own rotation speed is so fast that the length of a day here is 17.8 hours.
The planet Neptune is about 4500 million kilometers from the Sun, therefore, the light reaches the object in question in just over four hours.
Although the average density of Neptune is almost three times less than that of the Earth (it is 1.67 g/cm³), its mass is 17.2 times higher. This is explained by the large
Features of the composition, physical conditions and structure
Neptune and Uranus are planets that are based on solidified gases with a fifteen percent hydrogen content and a small amount of helium. As scientists suggest, the blue giant does not have a clear internal structure. The most probable is the fact that inside Neptune there is a dense core of small sizes.
The planet's atmosphere is made up of helium and hydrogen with minor admixtures of methane. Large storms often occur on Neptune, in addition, vortices and strong winds are characteristic of it. The latter blow in a westerly direction, their speed can reach up to 2200 km/h.
It has been observed that the speed of currents and flows in the giant planets increases with distance from the Sun. An explanation for this pattern has not yet been found. Thanks to the pictures taken by special equipment in the atmosphere of Neptune, it became possible to examine the clouds in detail. Just like Saturn or Jupiter, this planet has an internal source of heat. It is able to radiate up to three times more energy than it receives from the Sun.
Giant step forward
According to historical documents, Galileo saw Neptune on December 28, 1612. The second time he managed to observe the unknown on January 29, 1613. In both cases, the scientist took the planet for a fixed star, which is in conjunction with Jupiter. For this reason, Galileo is not credited with the discovery of Neptune.
It has been established that during the observation period of 1612 the planet was at a standing point, and just on the day when Galileo first saw it, it moved to a backward movement. This process is observed when the Earth overtakes the outer planet in its orbit. Since Neptune was not far from the station, its movement was too weak to be noticed by Galileo's insufficiently powerful telescope.
In 1781, Herschel managed to discover Uranus. Then the scientist calculated the parameters of its orbit. Based on the data obtained, Herschel concluded that there were mysterious anomalies in the process of movement of this space object: it was either ahead of the calculated one, or lagged behind it. This fact allowed us to assume that there is another planet behind Uranus, which distorts the trajectory of its movement by gravitational attraction.
In 1843, Adams was able to calculate the orbit of the mysterious eighth planet in order to explain the changes in the orbit of Uranus. The scientist sent data about his work to the astronomer of the king - J. Airey. Soon he received a response letter asking for clarification on some issues. Adams began to make the required sketches, but for some reason he never sent the message and did not subsequently initiate serious work on this issue.
The direct discovery of the planet Neptune was due to the efforts of Le Verrier, Galle and d'Are. On September 23, 1846, having at their disposal data on the system of elements of the orbit of the object they were looking for, they set to work to determine the exact location of the mysterious object. On the first evening, their efforts were crowned with success. The discovery of the planet Neptune at that time was called the triumph of celestial mechanics.
Name choice
After the discovery of the giant, they began to think about what name to give it. The very first option was proposed by Johann Galle. He wanted to christen the distant Janus in honor of the god symbolizing the beginning and end in ancient Roman mythology, but this name was not to the liking of many. The proposal of Struve, the director, was received much warmer. His version, Neptune, became final. The assignment of an official name to the giant planet put an end to numerous disputes and disagreements.
How did ideas about Neptune change?
Sixty years ago, information about the blue giant was different from today. Despite the fact that the sidereal and synodic periods of rotation around the Sun were relatively accurately known, the inclination of the equator to the plane of the orbit, there were data that were established less accurately. So, the mass was estimated at 17.26 Earth instead of the real 17.15, and the equatorial radius - at 3.89, and not 3.88 from our planet. As for the sidereal period of revolution around the axis, it was believed that it was 15 hours 8 minutes, which is fifty minutes less than the real one.
There were inaccuracies in some other parameters too. For example, before Voyager 2 got as close to Neptune as possible, it was assumed that the planet's magnetic field was similar in configuration to Earth's. In fact, it resembles in appearance the so-called inclined rotator.
A little about orbital resonances
Neptune is able to influence the Kuiper belt located at a great distance from it. The latter is represented by a ring of minor icy planets, similar to that between Jupiter and Mars, but with a much greater extent. The Kuiper belt is under a significant influence of the attraction of Neptune, as a result of which gaps have even formed in its structure.
The orbits of those objects that are held in the indicated belt for a long period are established by the so-called secular resonances with Neptune. AT certain cases this time is comparable to the period of existence of the solar system.
The zones of gravitational stability of Neptune are called. In them, the planet holds a large number of Trojan asteroids, as if dragging them along the entire orbit.
Features of the internal structure
In this regard, Neptune is similar to Uranus. The atmosphere accounts for about twenty percent of the total mass of the planet in question. The closer to the core, the higher the pressure. The maximum value is about 10 GPa. In the lower layers of the atmosphere there are concentrations of water, ammonia and methane.
Elements of the internal structure of Neptune:
- Upper clouds and atmosphere.
- Atmosphere formed by hydrogen, helium and methane.
- Mantle (methane ice, ammonia, water).
- Stone-ice core.
Climatic characteristic
One of the differences between Neptune and Uranus is the degree of meteorological activity. According to data received from the Voyager 2 spacecraft, the weather on the blue giant changes frequently and significantly.
It was possible to identify an extremely dynamic system of storms with winds that reach speeds of even 600 m / s - almost supersonic (most of them blow in the opposite direction to Neptune's rotation around its own axis).
In 2007, it was revealed that the upper troposphere of the planet's south pole is ten degrees Celsius warmer than the rest of the world, where the temperature is about -200 ºС. Such a difference is quite enough for methane from other zones of the upper atmosphere to seep into space in the region of the south pole. The resulting "hot spot" is a consequence of the axial tilt of the blue giant, the south pole of which has been facing the Sun for forty Earth years. As Neptune slowly moves in orbit to the opposite side of the indicated celestial body, the south pole will gradually completely go into shadow. Thus, Neptune will expose its north pole to the Sun. Consequently, the zone of methane release into space will move to this part of the planet.
"Accompanying" giant
Neptune is a planet that has, according to today's data, eight satellites. Among them, one large, three medium and four small. Let's take a closer look at the three biggest ones.
Triton
It is the largest satellite that the giant planet Neptune has. It was discovered by W. Lassell in 1846. Triton is 394,700 km from Neptune and has a radius of 1,600 km. It is supposed to have an atmosphere. The object is close in size to the Moon. According to scientists, before the capture of Neptune, Triton was an independent planet.
Nereid
This is the second largest satellite of the planet under consideration. On average, it is 6.2 million kilometers away from Neptune. The radius of the Nereid is 100 kilometers, and the diameter is twice that. In order to make one revolution around Neptune, this satellite needs 360 days, that is, almost an entire Earth year. The discovery of Nereid occurred in 1949.
Proteus
This planet ranks third not only in size, but also in distance from Neptune. This is not to say that Proteus has any special characteristics, but it was his scientists who chose to create a three-dimensional interactive model based on images from the Voyager 2 spacecraft.
The remaining satellites are small planets, of which there are a great many in the solar system.
Features of the study
Neptune - which planet is from the Sun? Eighth. If you know exactly where this giant is, you can see it even with powerful binoculars. Neptune is a rather difficult cosmic body to study. This is partly due to the fact that its brightness is slightly more than eighth magnitude. For example, one of the above satellites - Triton - has a brightness equal to fourteen magnitudes. In order to detect the disk of Neptune, high magnifications are required.
The Voyager 2 spacecraft managed to reach an object like Neptune. The planet (see photo in the article) received a guest from Earth in August 1989. Thanks to the data collected by this ship, scientists have at least some information about this mysterious object.
Data from Voyager
Neptune is the planet that had the Great Dark Spot in the southern hemisphere. This is the best-known detail about the object, obtained as a result of the operation of the spacecraft. In diameter, this Spot was almost equal to the Earth. The winds of Neptune carried it at a tremendous speed of 300 m / s in a westerly direction.
According to HST (Hubble Space Telescope) observations in 1994, the Great Dark Spot has disappeared. It is assumed that it either dissipated or was covered by other parts of the atmosphere. A few months later, thanks to the Hubble telescope, it was possible to discover a new Spot, which is already in the northern hemisphere of the planet. Based on this, we can conclude that Neptune is a planet whose atmosphere is changing rapidly - presumably due to slight fluctuations in the temperatures of the lower and upper clouds.
Thanks to Voyager 2, it was found that the described object has rings. Their presence was revealed in 1981, when one of the stars eclipsed Neptune. Observations from the Earth did not bring much result: instead of full rings, only faint arcs were visible. Once again, Voyager 2 came to the rescue. In 1989, the apparatus took detailed pictures of the rings. One of them has an interesting curved structure.
What is known about the magnetosphere
Neptune is a planet whose magnetic field is oriented rather strangely. The magnetic axis is 47 degrees inclined to the axis of rotation. On Earth, this would be reflected in the unusual behavior of the compass needle. Thus, the North Pole would be located south of Moscow. Another unusual fact is that Neptune has an axis of symmetry magnetic field does not pass through its center.
Questions without answers
Why does Neptune have such strong winds when it is very far from the Sun? For the implementation of such processes, the internal source of heat, located in the depths of the planet, is not strong enough.
Why is there a lack of hydrogen and helium at the facility?
How to develop a relatively inexpensive project to study Uranus and Neptune as fully as possible with the help of spacecraft?
Due to what processes is the unusual magnetic field of the planet formed?
Modern research
Creating accurate models of Neptune and Uranus in order to visually describe the process of formation of ice giants turned out to be a difficult task. To explain the evolution of these two planets put forward a considerable number of hypotheses. According to one of them, both giants appeared due to instability within the underlying protoplanetary disk, and later their atmospheres were literally blown away by the radiation of a large class B or O star.
According to another concept, Neptune and Uranus formed relatively close to the Sun, where the density of matter is higher, and then moved to their current orbits. This hypothesis has become the most common, since it can explain the existing resonances in the Kuiper belt.
Observations
Neptune - which planet is from the Sun? Eighth. And it is not possible to see it with the naked eye. The giant's magnitude is between +7.7 and +8.0. Thus, it is dimmer than many celestial objects, including the dwarf planet Ceres, and some asteroids. To organize high-quality observations of the planet, a telescope with at least two hundred times magnification and a diameter of 200-250 millimeters is required. With 7x50 binoculars, the blue giant will be visible as a faint star.
The change in the angular diameter of the considered space object is within 2.2-2.4 arc seconds. This is due to the fact that the planet Neptune is located at a very large distance from the Earth. It was extremely difficult to extract facts about the state of the surface of the blue giant. Much has changed with the advent of the Hubble Space Telescope and the most powerful ground-based instruments equipped with adaptive optics.
Observations of the planet in the radio wave range made it possible to establish that Neptune is a source of flashes of an irregular nature, as well as continuous radiation. Both phenomena are explained by the rotating magnetic field of the blue giant. Against a colder background in the infrared zone of the spectrum, disturbances in the depths of the planet's atmosphere, the so-called storms, are clearly visible. They are generated by heat emanating from the contracting core. Thanks to observations, you can determine their size and shape as accurately as possible, as well as track their movements.
The mysterious planet Neptune. Interesting Facts
For almost a century, this blue giant was considered the most distant in the entire solar system. And even the discovery of Pluto did not change this belief. Neptune - what planet is it? Eighth, not last, ninth. However, it sometimes turns out to be the farthest from our luminary. The fact is that Pluto has an elongated orbit, which is sometimes closer to the Sun than the orbit of Neptune. The blue giant managed to regain the status of the most distant planet. And all thanks to the fact that Pluto was transferred to the category of dwarf objects.
Neptune is the smallest of the four known gas giants. Its equatorial radius is smaller than that of Uranus, Saturn and Jupiter.
Like all gas planets, Neptune does not have a solid surface. Even if spaceship managed to get to him, he could not land. Instead, a dive deep into the planet would occur.
The gravity of Neptune is slightly more than the earth's (by 17%). This means that the force of gravity acts on both planets in almost the same way.
Neptune takes 165 Earth years to revolve around the Sun.
The blue saturated color of the planet is explained by the most powerful lines of such a gas as methane, which prevail in the reflected light of the giant.
Conclusion
The discovery of planets played a huge role in the process of space exploration. Neptune and Pluto, as well as other objects, were discovered as a result of the painstaking work of many astronomers. Most likely, what is now known to mankind about the Universe is only a small part of the real picture. Space is a great mystery, and it will take more than one century to unravel it.
Neptune- the last planet in terms of distance from the Sun. This name was given to the object in honor of the mythical character of the ancient Romans - the ruler of the seas.
Neptune was discovered in 1846. He became the first celestial body, which was discovered by accurate calculations. Other space objects were discovered in the course of regular research. Noticing strong changes in the orbit of Uranus, scientists of that time began to suspect the presence of another planet. A little later, Neptune was found in the proposed area. After this discovery, its largest moon, Triton, was also discovered.
History of the discovery of the planet Neptune
Carrying out his observations, Galileo took Neptune for a luminary in the night sky. For this reason, he was not recognized as the discoverer of the planet.
In 1612, Neptune approached the standing point. It was this moment that was transitional for the planet to reverse motion. It can be observed, for example, when the Earth begins to overtake the outer one in its orbit. And, due to the fact that Neptune was approaching the point of standing, its movement was very slow in order to fix this with the help of primitive devices of that time.
A little later - in 1821, the scientist Alexim Bouvard presented his tables of the orbit of Uranus. In the course of further activities to study the planet, significant inconsistencies between its real movement and these tables were noted. The Briton T. Hussey, based on the results of his work, put forward a version that the anomalies in the orbit of Uranus may have been caused by another celestial object. In 1834, Hussey and Bouvard met, at which the latter promised to carry out new calculations necessary to determine the location of the new planet. But it is known that after this meeting, Bouvard was no longer interested in this topic. In 1843, D. Cooch Adams managed to calculate the orbit of an unknown planet in order to "justify" discrepancies in the orbit of Uranus. The astronomer sent the results of his work to George Airy, who was Astronomer Royal. But, as it turned out, he did not take seriously the consideration of the details of this case.
Urbain Le Verrier in 1845 began his own calculations. But the staff of the main observatory in Paris refused to take the ideas of the scientist seriously and to contribute to the search for the 8th planet. In 1846, having studied Le Verrier's work on estimating the longitude of an object and making sure that his result was similar to Adams' Results, Airy asked D. Challis, head of the Cambridge Observatory, to start searching anyway. Challis himself had repeatedly seen Neptune in the night sky. But due to the fact that the astronomer kept postponing the analysis of observations, he also failed to become its discoverer.
After some time, Le Verrier convinces an employee of the Berlin Observatory, Johann Galle, of the success of the planned research. Then Heinrich D. Arre invites Halle to make comparisons with the previously created map of a part of the sky with the new coordinates presented by Le Verrier. This was necessary to determine the direction of movement of the object against the background of stars. Neptune was discovered on the same night. Then, for 2 days, scientists continued to observe the region of the sky, which Le Verrier identified. They needed to make sure that this object is actually a planet. So, September 23, 1846 is the official date of discovery of the 8th planet of our star system.
A little later, because of this event, many disputes arose between French and English scientists about who should be considered the discoverer. As a result, they were recognized immediately by two scientists - Adams and Le Verrier. But after the discovery of papers in 1998, secretly appropriated by J. Eggen, it turned out that Le Verrier has much more right to be called the discoverer of Neptune than his colleague. 
Name
The eighth planet did not immediately receive its rightful name. Some time after its discovery in the circle of scientists, it was designated as "the outer planet from Uranus." Some simply referred to it as "Planet Le Verrier". For the first time, the name for the object was proposed by Halle. The scientist recommended to call it "Janus". The Englishman Chiles suggested the name "Ocean".
But as a discoverer, Le Verrier felt that it was he who should name the object he discovered. The scientist decided to call it Neptune, referring to the approval of this decision by the French bureau of longitudes. It is known that earlier the astronomer wanted to name the planet after himself, but this decision caused a protest abroad.
Vasily Struve, the head of the Pulkovo Observatory, considered "Neptune" the most appropriate name for the planet. The ancient Romans considered Neptune the patron of the seas, just like the Greeks Poseidon.
Status of the planet Neptune
After being discovered until the 30th year of the last century, Neptune was considered the extreme large object of the solar system. But after the later discovery of Pluto, Neptune became the penultimate planet. But with a careful study of the Kuiper belt, scientists tried to decide on the following question: should Pluto be considered a planet, or should it be considered an inhabitant of the Kuiper belt? Only in 2006, it was decided to leave Pluto the status of a dwarf planet. So Neptune was again considered the last planet in the solar system.
The evolution of the concept of the planet Neptune
In the middle of the last century, information about Neptune was radically different from today's data. For example, earlier the mass of Neptune was equated to 1726 Earth, instead of the actual 1515. It was also assumed that the size of the equator radius is 3.00, instead of the real 3.88 of the Earth's radius.
Also, until the full exploration of Neptune by Voyager 2, its magnetic field was believed to be identical to the magnetic fields of Earth and Saturn. But after long observations, it turned out that it has the shape of an "oblique rotator".
Physical characteristics of the planet Neptune
Having a mass of 1.0243 1026 kg, we can say that Neptune in its dimensions occupies a middle position between the Earth and large gas planets. Its mass indicators are 17 times higher than on Earth. While Neptune is only 1⁄19 the mass of Jupiter. Uranus and Neptune are considered to be a subclass of gas giants. They are sometimes referred to as "ice giants". This is due to their "modest" dimensions and high concentration of light elements. Neptune is also used in the study of exoplanets as a metonym. Known cosmic bodies with identical masses are often called "Neptunes".
Orbit and rotation of the planet Neptune
The distance between Neptune and our star is 4.55 billion km. Neptune completes a full cycle around it in almost 165 years. The planet itself is located at a distance of 4.3036 billion km from the Earth. In 2011, Neptune completed its first orbit around the star since its discovery.
The sidereal period of Neptune's revolution is 16.11 hours. Due to the fact that the surface of Neptune is not solid, the principle of rotation of its atmosphere is characterized as differential. The equatorial region of the planet circulates with an 18-hour period. This is relatively slow compared to the speed at which Neptune's magnetic field rotates. Its polar regions make a full revolution around themselves in 12 Earth hours. Of all the objects that live in the inner part of our solar system, this principle of rotation is observed only in Neptune. This phenomenon is the root cause of the latitudinal wind shift. 
Orbital resonances
It is known that Neptune has a fairly strong influence even on the bodies of the Kuiper belt. It must be recalled that this belt is a kind of ring. It includes small-sized ice planets. The belt is somewhat similar to the asteroid belt located between Jupiter and Mars. The Kuiper belt originates from a certain zone of Neptune's orbit (30 AU) and extends up to 55 AU from the star. The influence of Neptune's gravity on Kuiper belt objects is significant. It is known that for all the existence of the solar system, many objects were "brought" out of the belt region under the influence of Neptune's gravity. As a result, voids formed in the place of the disappeared bodies.
The orbits of objects held in the region of this belt, for significant periods of time, are determined by secular resonances with Neptune. Of these, there are those for which these intervals are comparable with the entire period of the existence of our star system.
Atmosphere and climate
The internal structure of Neptune
If we talk about the internal structure of the planet, then it should be noted how it is similar to the internal structure of the planet Uranus. The very atmosphere of Neptune is about 10-20% of its total mass. In the core zone, the pressure reaches 10 GPa. The lowest layers of the atmosphere are saturated with large amounts of methane, ammonia and water.
The internal structure of the planet Neptune:
1. The upper atmospheric layer, including cloud formations located at its high levels.
2. An atmosphere dominated by methane, hydrogen and helium.
3. The mantle, which contains a significant amount of methane ice, water and ammonia.
4. Rock-ice core with time dark and strongly heated area begins to transform into a liquid mantle. The indicators of its temperature range from 2000 to 5000 K. The mass indicators of the mantle exceed those of the earth by 10-15 times. Scientists believe that it is saturated with large amounts of methane, water and ammonia. This matter is also called ice according to the terms established among scientists. And this, despite the fact that in reality she is very hot. The liquid mantle has excellent electrical conductivity. That is why it is often called the ocean of liquid ammonia. Scientists believe that the core of Neptune envelops the "diamond liquid". Its mass is about 1.2 times that of the earth. The core consists mostly of the following elements: nickel, silicates and iron.
The magnetosphere of the planet Neptune
With its magnetic field and magnetosphere, it is very similar to Uranus. They are also quite strongly inclined from the axis of the planet. Prior to Voyager 2's study of Neptune, astrophysicists believed that the tilt of Uranus' magnetosphere was a so-called "side effect" of lateral rotation. But today, having received more information, scientists are convinced that this feature of the magnetosphere is explained by the action of tides in the inner zones.
The planet's magnetic field has a complex geometry. It includes significant inclusions from non-bipolar components, such as the quadripole moment. In terms of its power, it surpasses the dipole one. For example, for the Earth, Saturn and Jupiter it is relatively small, and therefore their fields do not “depart” so much from the axis.
The bow shock wave of the planet is a region of the magnetosphere in which a change in the speed of the solar wind occurs. Here his movement begins to noticeably slow down. This zone is located at a distance measured in 34.9 planetary radii. The magnetopause is the zone where the solar winds are balanced by strong pressure. It is located at a distance of 25 radii of the planet. The length of the magnetotail extends for a distance equal to 72 radii or more.
Atmosphere of the planet Neptune
Neptune's upper atmosphere contains helium (19%) and hydrogen (80%). Methane is also found here in small quantities. Its visible absorption bands are visible in infrared observations. It is known that methane absorbs red color well, which is why the atmosphere of the planet has a predominantly blue tint.
The percentage of methane in the atmosphere of Neptune is almost the same as that of Uranus. Therefore, scientists suggest that there is another special element that gives the atmosphere a bluish tint.
Neptune's atmosphere is divided into the troposphere and stratosphere. In the troposphere, temperature decreases with distance from the surface. And in the stratosphere, on the contrary, the temperature rises as it approaches the surface. The boundary "cushion" between them is the tropopause. It consists of cloud formations with different chemical composition.
At a pressure estimated at 5 bar, ammonia and hydrogen sulfide clouds begin to form. At pressures above 5 bar, new clouds of ammonium sulfide and water form. As you approach the surface of the planet, at a pressure of 50 bar, clouds of water vapor appear.
High-level cloud formations were observed by Voyager 2 by their shadows, which were projected onto the dense lower layer. It was also possible to make out the cloud bands "enveloping" the planet.
Careful studies of Neptune have helped scientists discover that low levels of its stratosphere are clouded by the fumes from ultraviolet photolysis of methane. In the stratosphere of Neptune were also found: hydrogen cyanide and carbon monoxide. In general, the temperature of Neptune's stratosphere is much higher than that of Uranus' stratosphere. The reason for this is the highest percentage of carbon in it. For unknown reasons, Neptune's thermosphere has an extremely high temperature - 750 K. This is not typical for a planet that is at a fairly large distance from the Sun. This means that at such a distance the thermosphere cannot be heated by ultraviolet radiation to such a level. Scientists believe that this anomaly is associated with the interaction of the thermosphere with the ions of the magnetic field of Neptune. There is also another version explaining this phenomenon. It is believed that the heating of the thermosphere is carried out with the supply of gravity waves from the inner part of the planet. Then they simply dissipate in the atmosphere. It is known that traces of carbon monoxide and water are present in the thermosphere. Astrophysicists believe that they were here through external sources.
The climate of the planet Neptune
Storms and winds prevail on Neptune, reaching speeds of up to 600 m/s. In the process of observing the principle of cloud movement, scientists calculated another pattern: the speed of the winds changes when moving from the eastern region to the western one. At the upper levels of the atmosphere, winds predominate, average speed whose movement is equal to 400 m/s. In the zone of the equator and poles - 250 m/s.
Neptune's winds mostly blow in the opposite direction of its rotation. The scheme of wind movement compiled by scientists indicates that at higher latitudes the direction of the winds still coincides with the direction of rotation of the planet around its axis. At lower latitudes, the winds move predominantly in the opposite direction. Scientists believe that the explanation for these differences is the "skin effect", and not other atmospheric processes. In the atmosphere of the planet, acetylene, methane and ethane are found in greater quantities than in the zone of its poles.
These observations are practically an explanation for the existence of upwelling in the equatorial zone of the planet. In 2007, it was found that the temperature in the upper troposphere is 10 degrees higher than in the rest of the planet. Such a significant difference, according to scientists, affected methane, which was originally in a frozen state. He began to seep into outer space through the south pole of Neptune. main reason this anomaly is generally believed to be the angle of inclination of the object itself.
As the planet moves towards the opposite side of the star, its south pole will begin to become obscured. This indicates that Neptune will be facing the star with its north pole. And the "release" of methane into space will now be carried out from the region of the north pole.
Storms on the planet Neptune
In 1989, the Voyage 2 spacecraft discovered the Great Dark Spot. It is a persistent storm with dimensions reaching 13,000 × 6,600 km. Scientists associated this anomaly with the famous "Great Red Spot" present on Jupiter. But in 1994, the Hubble Space Telescope did not detect Neptune's dark spot at the spot where it was recorded by Voyager 2. Instead of a black spot, another formation was seen here - Stulker. This is a storm recorded south of the Great Dark Spot. The Little Dark Spot is the second most powerful storm that was discovered during the approach of the machine to the planet, which occurred in 1989. At first it was visualized as a dark area. But as Voyager 2 approached Neptune, its outlines in the images became clearer, due to which scientists immediately noticed various cloud formations on it: dense, more rarefied, bright and dark.
Astrophysicists believe that darker spots form in the lower layers of the troposphere than brighter and rarefied clouds.
These storms are stable with an average lifespan of up to several months. So we can conclude that they have a vortex structure. The brighter clouds of methane, which are born in the tropopause, merge best with dark spots.
The persistence of these clouds indicates that the old "dark spots" may yet continue to exist as cyclones. But in this case, their dark color will be lost. These formations can dissipate if they are near the equator.
The internal heat of the planet Neptune
Despite the fact that Neptune and Uranus are similar in many ways, Neptune has much more weather diversity. This is due to its increased internal temperature. And this, despite the fact that Neptune is located at a greater distance from the Sun than Uranus.
The surface temperatures of these planets are approximately the same. In the upper layers of the troposphere of Neptune, the temperature is -222°C. In the depths at a pressure of 1 bar, the temperature readings are -201°C. The deeper lower layers are composed of gases, but the temperature in this area rises. The reason for such a distribution of heat, as well as the principle of heating, has not yet been clarified by scientists. It is only known that Uranus emits 1.1 times more energy than it receives from a star. From Neptune comes 2.61 times more quantity energy than it receives from the sun. The amount of heat it produces is equal to 161% of the stellar energy it receives. Despite the fact that Neptune is the planet most distant from the star, its energy potential is enough to wind up to incredible speeds that can only be within the solar system. Scientists give several interpretations to this phenomenon at once. Perovoe - radiogenic heating, carried out by the "heart" (core) of Neptune. The second is the conversion of methane into chain hydrocarbons. The third is convection occurring in deeper atmospheric layers, which provokes the slowing down of gravitational waves over the tropopause region.
The formation and migration of the planet Neptune
Scientists even today find it difficult to recreate the formation of ice giants, which include Neptune and Uranus. Current models indicate that the density of matter in the outer zone of the solar system was too low for the formation of objects of this size by accretion of matter onto the core. Today there are many hypotheses about the evolution of these two bodies. The essence of one of the most common theories is that these icy planets were formed due to the instability of the protoplanetary disk. And already at the last stages of the formation of their atmosphere, they began to be carried away into space under the influence of massive luminaries of class B and O.
The essence of the less popular hypothesis is that Neptune and Uranus were formed at a minimum distance from the Sun. In this area, the density of matter was higher, and soon the planets were in their current orbits. The theory about the "transition" of Neptune is well known. It implies that as Neptune moved outward, it systematically intersected with bodies belonging to the Kuiper proto-belt. The planet formed new resonances and randomly "corrected" the current orbits. It is assumed that the bodies of the scattered disk have such a position due to this resonant effect, provoked by the migration of Neptune.
In 2004, Allesandro Mobidelli proposed a new model. Its essence is the approach of Neptune to the Kuiper belt, provoked by a 1:2 resonant formation in the orbit of Saturn and Neptune. They played the role of gravitational boosters, pushing Neptune and Uranus into new orbits. In addition, such a resonance contributed to a change in their location. It is possible that the reason for the expulsion of bodies from the Kuiper Belt region was the "Late Heavy Bombardment". According to scientists, it occurred 600 million years after the completion of the formation of the solar system.
Satellites and rings
Moons of the planet Neptune
Today there are 14 known moons of Neptune. The mass of the largest is 99.5% of the total mass of all the moons of the planet. This object was named Triton. It was discovered by William Lassell. This happened exactly 15 days after the official announcement of the discovery of Neptune. Unlike other moons in the solar system, Triton has a retrograde orbit. It is possible that it was pulled by the gravity of Neptune, and was not formed in its current place of circulation. Many scientists believe that it could have originally been a dwarf planet belonging to the Kuiper belt. Due to the effect of tidal acceleration, Triton is spiraling and rather slowly moving towards Neptune. It will eventually collapse when it approaches the Roche limit. As a result, a new ring is formed, which in terms of massiveness can be compared with the rings of Saturn. According to scientists, this event will occur in 10-100 million years.
In 1989, scientists obtained data on the temperature prevailing on Triton. She left -235 °C. At that time, this was the smallest value for the bodies of our star system, which have geological activity. Triton is one of the three moons in the solar system that have an atmosphere. Two of them are Titan and Io. Astronomers also do not exclude the presence of an internal liquid ocean in Triton.
The second most discovered satellite of Neptune is Nereid. It also has an irregular shape. The eccentricity of its orbit is considered the highest of all such bodies in the inner region of the solar system.
In the fall of 1989, the Voyager 2 machine managed to detect the presence of 6 new satellites near Neptune. To a small extent, the attention of scientists was attracted by Proteus, which has an irregular shape similar to Triton. Astronomers singled it out because it wasn't pulled into a spherical shape by its own gravity. This means that Proteus, in all likelihood, has a huge density.
The closest satellites of Neptune are: Naiad, Galatea, Thalassa and Despita. The orbits of these bodies are so close to the planet that they affect the zone of the planet's rings. Larissa was actually discovered in 1981 during observations of the overlap of the sun, recorded by Voyager 2. But in 1989, when the car approached the minimum distance to Neptune, it turned out that with this coverage, a satellite image was taken. In 2002-2003, the Hubble machine recorded the last, smallest known satellite of Neptune.
Rings of the planet Neptune
Neptune, like Saturn, has a ring system. These rings, according to scientists, consist of ice fragments that are covered with silicates. Some astronomers believe that their main component may be carbon compounds, which give the rings a reddish tint.
Observations of the planet Neptune
Neptune is impossible to see without special equipment. And all because it has too low brightness. And this means that the satellites of Jupiter, the asteroids 2 Pallas, 6 Heba, 4 Vesta, 7 Iris and 3 Juno will be brighter than it in the night sky. For professional observations of the planet, you need a telescope with a magnification of 200x or more. Only with such an apparatus can one see the bluish disk of Neptune, reminiscent of Uranus. In simpler devices, such as binoculars, Neptune will be visualized as a dim star.
Due to the considerable distance between the Earth and Neptune, its angular diameter changed only in the limit from 2.2 to 2.4 arcsec. sec. This value is the smallest against the background of the values of other planets in the solar system. That is why it is impossible to observe the planet with the naked eye. Earlier, when scientists carried out research using more primitive devices, the accuracy of most information about Neptune was low. Only with the advent of the Hubble space machine were astronomers able to obtain reliable information about the eighth planet in the solar system.
As far as ground observations are concerned, every 367th day Neptune goes into retrograde motion. As a result, illusory loops begin to form, which are especially noticeable against the background of stars during each confrontation. In 2010 and 2011, according to these loops, the planet was brought to the coordinates at which it was at the time of discovery - in 1846.
A study of Neptune conducted in the radio wave range showed that it systematically emits flares. This to some extent explains the principle of rotation of the magnetic field of Neptune.
Exploration of the planet Neptune
Voyager 2 made its closest approach to Neptune in 1989. During this mission, the spacecraft was also able to approach Triton. When approaching, the signals sent by the apparatus reached the Earth in 246 minutes. In this regard, almost the entire Voyager 2 mission was carried out through pre-loaded programs designed to control during the approach to Neptune and its large satellite. First, Voyager 2 managed to approach Nereid, and only then approach the planet's atmosphere. After that, the car flew next to Triton.
Voyager 2 was able to confirm scientists' guesses about the existence of a magnetic field. During this mission, it was also possible to clarify questions about the inclination of the orbit. The car's journey to Neptune also helped to learn about its active weather system. Voyager 2 discovered 6 moons and rings of Neptune. In 2016, NASA was planning a new mission called the Neptune Orbiter. But today, the leaders of the space agency do not even mention its implementation.
Neptune is the eighth and most distant planet in the solar system. Neptune is also the fourth largest planet by diameter and the third largest by mass. The mass of Neptune is 17.2 times, and the diameter of the equator is 3.9 times that of the Earth. The planet was named after the Roman god of the seas. His astronomical symbol Neptune symbol.svg is a stylized version of Neptune's trident.
Discovered on September 23, 1846, Neptune was the first planet to be discovered through mathematical calculations rather than through regular observations. The discovery of unforeseen changes in the orbit of Uranus gave rise to the hypothesis of an unknown planet, the gravitational perturbing influence of which they are due to. Neptune was found within the predicted position. Soon, its satellite Triton was also discovered, but the remaining 12 satellites known today were unknown until the 20th century. Neptune was visited by only one spacecraft, Voyager 2, which flew close to the planet on August 25, 1989.
Neptune is close in composition to Uranus, and both planets differ in composition from the larger giant planets Jupiter and Saturn. Sometimes Uranus and Neptune are placed in a separate category of "ice giants". Neptune's atmosphere, like that of Jupiter and Saturn, is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but contains a higher proportion of ices: water, ammonia, methane. The core of Neptune, like Uranus, consists mainly of ice and rocks. Traces of methane in the outer atmosphere, in particular, are the cause of blue color planets.
In the atmosphere of Neptune, the strongest winds among the planets of the solar system rage, according to some estimates, their speeds can reach 2100 km / h. During the Voyager 2 flyby in 1989 southern hemisphere Neptune was discovered so-called Great Dark Spot, similar to the Great Red Spot on Jupiter. The temperature of Neptune in the upper atmosphere is close to -220 °C. At the center of Neptune, the temperature is various estimates from 5400 K to 7000-7100 °C, which is comparable to the temperature on the surface of the Sun and comparable to the internal temperature of most known planets. Neptune has a faint and fragmented ring system, possibly discovered as early as the 1960s, but not reliably confirmed by Voyager 2 until 1989.
In 1948, in honor of the discovery of the planet Neptune, it was proposed to name a new chemical element at number 93 neptunium.
July 12, 2011 marks exactly one Neptunian year, or 164.79 Earth years, since the discovery of Neptune on September 23, 1846.
Name
For some time after the discovery, Neptune was simply referred to as "the outer planet from Uranus" or as the "planet of Le Verrier". The first to come up with the idea of an official name was Galle, who proposed the name "Janus". In England, Chiles suggested another name: "Ocean".
Claiming that he had the right to name the planet he discovered, Le Verrier proposed to call it Neptune, falsely claiming that such a name was approved by the French bureau of longitudes. In October, he tried to name the planet after himself, Le Verrier, and was supported by the director of the observatory, François Arago, but this initiative ran into significant resistance outside of France. The French almanacs very quickly returned the name Herschel for Uranus, in honor of its discoverer William Herschel, and Le Verrier for the new planet.
Director of the Pulkovo Observatory Vasily Struve preferred the name "Neptune". He announced the reasons for his choice at the congress of the Imperial Academy of Sciences in St. Petersburg on December 29, 1846. This name received support outside of Russia and soon became the generally accepted international name for the planet.
In Roman mythology, Neptune is the god of the sea and corresponds to the Greek Poseidon.
Status
From its discovery until 1930, Neptune was the farthest known planet from the Sun. After the discovery of Pluto, Neptune became the penultimate planet, except for the years 1979-1999, when Pluto was inside the orbit of Neptune. However, the study of the Kuiper Belt in 1992 led many astronomers to debate whether Pluto was a planet or part of the Kuiper Belt. In 2006, the International Astronomical Union adopted a new definition of the term "planet" and classified Pluto as a dwarf planet, and thus again made Neptune the last planet in the solar system.
The evolution of ideas about Neptune
Back in the late 1960s, ideas about Neptune were somewhat different from today. Although the sidereal and synodic periods of revolution around the Sun were relatively accurately known, the average distance from the Sun, the inclination of the equator to the plane of the orbit, there were parameters measured less accurately. In particular, the mass was estimated at 17.26 Earth instead of 17.15; equatorial radius of 3.89 instead of 3.88 from the earth. The star period of rotation around the axis was estimated at 15 hours 8 minutes instead of 15 hours and 58 minutes, which is the most significant discrepancy between current knowledge about the planet and knowledge of that time.
At some points, there were discrepancies later. Initially, before the flight of Voyager 2, it was assumed that the magnetic field of Neptune has the same configuration as the field of the Earth or Saturn. According to the latest ideas, the field of Neptune has the form of the so-called. "tilted rotator". The geographic and magnetic "poles" of Neptune (if we represent its field as a dipole equivalent) turned out to be at an angle to each other of more than 45 °. Thus, when the planet rotates, its magnetic field describes a cone.
Comparison of the sizes of the Earth and Neptune
With a mass of 1.0243 1026 kg, Neptune is an intermediate link between the Earth and the large gas giants. Its mass is 17 times that of the Earth, but is only 1/19 of the mass of Jupiter. The equatorial radius of Neptune is 24,764 km, which is almost 4 times the earth's. Neptune and Uranus are often considered a subclass of gas giants, referred to as "ice giants" due to their smaller size and higher concentrations of volatiles. When searching for exoplanets, Neptune is used as a metonym: discovered exoplanets with a similar mass are often called "Neptunes", and astronomers often use Jupiter ("Jupiters") as a metonym.
Orbit and rotation
For one complete revolution of Neptune around the Sun, our planet makes 164.79 revolutions.
The average distance between Neptune and the Sun is 4.55 billion km (about 30.1 average distances between the Sun and the Earth, or 30.1 AU), and it takes 164.79 years to make a full revolution around the Sun. The distance between Neptune and the Earth is from 4.3 to 4.6 billion km. On July 12, 2011, Neptune completed its first full orbit since the discovery of the planet in 1846. From Earth, it will be visible differently than on the day of discovery, as a result of the fact that the period of the Earth's revolution around the Sun (365.25 days) is not a multiple of the period of revolution of Neptune. The planet's elliptical orbit is tilted 1.77° relative to the Earth's orbit. Due to the presence of an eccentricity of 0.011, the distance between Neptune and the Sun changes by 101 million km - the difference between perihelion and aphelion, that is, the closest and most distant points of the planet's position along the orbital path. Neptune's axial tilt is 28.32°, which is similar to the axial tilt of Earth and Mars. As a result, the planet experiences similar seasonal changes. However, due to Neptune's long orbital period, the seasons last for forty years each.
The sidereal rotation period for Neptune is 16.11 hours. Due to an axial tilt similar to Earth's (23°), changes in the sidereal rotation period during its long year are not significant. Since Neptune does not have a solid surface, its atmosphere is subject to differential rotation. The wide equatorial zone rotates with a period of approximately 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field. In contrast to the equator, the polar regions rotate in 12 hours. Among all the planets of the solar system, this type of rotation is most pronounced in Neptune. This leads to a strong latitudinal wind shift.
Orbital resonances
The diagram shows the orbital resonances caused by Neptune in the Kuiper belt: 2:3 resonance (Plutino), "classical belt", with orbits not significantly affected by Neptune, and 1:2 resonance (Tutino)
Neptune renders big influence to the Kuiper belt, which is very distant from it. The Kuiper belt is a ring of icy minor planets, similar to the asteroid belt between Mars and Jupiter, but much longer. It ranges from the orbit of Neptune (30 AU) to 55 astronomical units from the Sun. The gravitational force of attraction of Neptune has the most significant influence on the Kuiper cloud (including in terms of the formation of its structure), comparable in proportion to the influence of Jupiter's force of attraction on the asteroid belt. During the existence of the solar system, some regions of the Kuiper belt were destabilized by Neptune's gravity, and gaps formed in the structure of the belt. An example is the region between 40 and 42 AU. e.
The orbits of objects that can be held in this belt for a sufficiently long time are determined by the so-called. secular resonances with Neptune. For some orbits, this time is comparable to the time of the entire existence of the solar system. These resonances appear when the period of revolution of an object around the Sun correlates with the period of revolution of Neptune as small integers, for example, 1:2 or 3:4. In this way, objects mutually stabilize their orbits. If, for example, an object rotates around the Sun twice as slow as Neptune, then it will go exactly half the way, while Neptune will return to its initial position.
The most densely populated part of the Kuiper Belt, with over 200 known objects, is in a 2:3 resonance with Neptune]. These objects make one rotation every 1? rotation of Neptune and are known as "plutino" because among them is one of the largest objects of the Kuiper belt - Pluto. Although the orbits of Neptune and Pluto intersect, the 2:3 resonance will prevent them from colliding. In other, less populated areas, there are 3:4, 3:5, 4:7 and 2:5 resonances. At its Lagrange points (L4 and L5), zones of gravitational stability, Neptune holds many Trojan asteroids, as if dragging them along its orbit. Neptune's Trojans are in 1:1 resonance with it. Trojans are very stable in their orbits and therefore the hypothesis of their capture by Neptune's gravitational field is unlikely. Most likely, they formed with him.
Internal structure
The internal structure of Neptune resembles the internal structure of Uranus. The atmosphere makes up approximately 10-20% of the total mass of the planet, and the distance from the surface to the end of the atmosphere is 10-20% of the distance from the surface to the core. Near the core, the pressure can reach 10 GPa. Volumetric concentrations of methane, ammonia and water are found in the lower layers of the atmosphere.
The internal structure of Neptune:
1. Upper atmosphere, upper clouds
2. Atmosphere of hydrogen, helium and methane
3. A mantle made of water, ammonia and methane ice
4. Stone-ice core
Gradually, this darker and hotter region condenses into an overheated liquid mantle, where temperatures reach 2000-5000 K. The mass of Neptune's mantle exceeds the earth's by 10-15 times, according to various estimates, and is rich in water, ammonia, methane and other compounds. According to the terminology generally accepted in planetology, this matter is called icy, even though it is a hot, very dense liquid. This highly electrically conductive liquid is sometimes referred to as the aqueous ammonia ocean. At a depth of 7000 km, conditions are such that methane decomposes into diamond crystals, which "fall" onto the core. According to one hypothesis, there is a whole ocean of "diamond liquid". Neptune's core is composed of iron, nickel and silicates and is believed to have a mass 1.2 times that of Earth. The pressure in the center reaches 7 megabars, that is, about 7 million times more than on the surface of the Earth. The temperature in the center may reach 5400 K.
Magnetosphere
Both in its magnetosphere and in its magnetic field, strongly inclined at 47° relative to the planet's axis of rotation, and extending to 0.55 of its radius (approximately 13,500 km), Neptune resembles Uranus. Before Voyager 2 arrived at Neptune, scientists believed that Uranus's tilted magnetosphere was the result of its "lateral rotation." However, now, after comparing the magnetic fields of these two planets, scientists believe that such a strange orientation of the magnetosphere in space may be caused by tides in the inner regions. Such a field may be due to the convective movement of fluid in a thin spherical interlayer of electrically conductive fluids of these two planets (a supposed combination of ammonia, methane and water), which drives a hydromagnetic dynamo. The magnetic field on the equatorial surface of Neptune is estimated at 1.42 T for a magnetic moment of 2.16 1017 Tm. Neptune's magnetic field has a complex geometry that includes relatively large inclusions from non-bipolar components, including a strong quadrupole moment that can be stronger than a dipole one. In contrast, the Earth, Jupiter and Saturn have a relatively small quadrupole moment, and their fields are less deviated from the polar axis. The bow shock wave of Neptune, where the magnetosphere begins to slow down the solar wind, passes at a distance of 34.9 planetary radii. The magnetopause, where the pressure of the magnetosphere balances the solar wind, is located at a distance of 23-26.5 Neptune radii. The magnetotail extends to about 72 Neptune radii, and very likely much further.
Atmosphere
In the upper layers of the atmosphere, hydrogen and helium were found, which account for 80 and 19%, respectively, at a given altitude. There are also traces of methane. Noticeable methane absorption bands occur at wavelengths above 600 nm in the red and infrared parts of the spectrum. As with Uranus, the absorption of red light by methane is a major factor in giving Neptune's atmosphere a blue tint, although Neptune's bright azure differs from Uranus's more moderate aquamarine. Since the methane content in Neptune's atmosphere is not much different from that of Uranus, it is assumed that there is also some, as yet unknown, component of the atmosphere that contributes to the formation of blue. The atmosphere of Neptune is divided into 2 main regions: the lower troposphere, where the temperature decreases with height, and the stratosphere, where the temperature, on the contrary, increases with height. The boundary between them, the tropopause, is at a pressure level of 0.1 bar. The stratosphere gives way to the thermosphere at a pressure level lower than 10-4 - 10-5 microbars. The thermosphere gradually passes into the exosphere. Models of Neptune's troposphere suggest that, depending on height, it consists of clouds of variable composition. Upper level clouds are in the pressure zone below one bar, where the temperature favors the condensation of methane.
A photo taken by Voyager 2 shows the vertical relief of clouds
At pressures between one and five bar, clouds of ammonia and hydrogen sulfide form. At pressures greater than 5 bar, clouds may consist of ammonia, ammonium sulfide, hydrogen sulfide and water. Deeper, at a pressure of approximately 50 bar, clouds of water ice can exist at a temperature of 0 °C. Also, it is possible that clouds of ammonia and hydrogen sulfide can be found in this zone. High-altitude clouds of Neptune were observed by the shadows they cast on the opaque cloud layer below the level. Among them, cloud bands stand out, which “wrap” around the planet at a constant latitude. These peripheral groups have a width of 50-150 km, and they themselves are 50-110 km above the main cloud layer. A study of Neptune's spectrum suggests that its lower stratosphere is hazy due to the condensation of ultraviolet photolysis products of methane, such as ethane and acetylene. Traces of hydrogen cyanide and carbon monoxide have also been found in the stratosphere. The stratosphere of Neptune is warmer than the stratosphere of Uranus due to the higher concentration of hydrocarbons. For unknown reasons, the planet's thermosphere has an abnormally high temperature of about 750 K. For such a high temperature, the planet is too far from the Sun for it to heat up the thermosphere with ultraviolet radiation. Perhaps this phenomenon is a consequence of atmospheric interaction with ions in the planet's magnetic field. According to another theory, the basis of the heating mechanism is gravity waves from the inner regions of the planet, which are scattered in the atmosphere. The thermosphere contains traces of carbon monoxide and water, which may have come from outside sources such as meteorites and dust.
Climate
One of the differences between Neptune and Uranus is the level of meteorological activity. Voyager 2, flying near Uranus in 1986, recorded extremely weak atmospheric activity. In contrast to Uranus, Neptune showed noticeable weather changes during the Voyager 2 image in 1989.
Great Dark Spot (top), Scooter (white cloud in the middle), and Small Dark Spot (bottom)
The weather on Neptune is characterized by an extremely dynamic system of storms, with winds sometimes reaching supersonic speeds (about 600 m/s). In the course of tracking the movement of permanent clouds, a change in wind speed was recorded from 20 m/s in the east direction to 325 m/s in the west direction. In the upper cloud layer, wind speeds vary from 400 m/s along the equator to 250 m/s at the poles. Most of the winds on Neptune blow in the opposite direction of the planet's rotation on its axis. The general scheme of winds shows that at high latitudes the direction of the winds coincides with the direction of rotation of the planet, and at low latitudes it is opposite to it. Differences in the direction of air currents are believed to be due to the "skin effect", and not to any deep atmospheric processes. The content of methane, ethane and acetylene in the atmosphere in the equator region exceeds the content of these substances in the region of the poles by tens and hundreds of times. This observation can be considered evidence in favor of the existence of upwelling at Neptune's equator and its lowering closer to the poles. In 2007, it was observed that the upper troposphere of Neptune's south pole was 10°C warmer than the rest of Neptune, which averages -200°C. This difference in temperature is enough for methane, which is frozen in other regions of Neptune's upper atmosphere, to seep into space at the south pole. This "hot spot" is a consequence of the axial tilt of Neptune, whose south pole has been facing the Sun for a quarter of a Neptunian year, that is, about 40 Earth years. As Neptune slowly orbits to the opposite side of the Sun, the south pole will gradually go into shadow, and Neptune will expose the sun to the north pole. Thus, the release of methane into space will move from the south pole to the north. Due to seasonal changes, Neptune's southern hemisphere cloud bands have been observed to increase in size and albedo. This trend was noticed as early as 1980 and is expected to continue into 2020 as the new season begins on Neptune. The seasons change every 40 years.
Storms
The Great Dark Spot, photographed by Voyager 2
In 1989, the Great Dark Spot, a persistent anticyclone storm measuring between 13,000 and 6,600 km, was discovered by NASA's Voyager 2. This atmospheric storm resembled the Great Red Spot of Jupiter, but on November 2, 1994, the Hubble Space Telescope did not detect it in its original place. Instead, a new similar formation was discovered in the northern hemisphere of the planet. Scooter is another storm found south of the Bolshoi dark spot. Its name is a consequence of the fact that even a few months before the approach of Voyager 2 to Neptune, it was clear that this group of clouds was moving much faster than the Great Dark Spot. Subsequent images made it possible to detect even faster than the "scooter" groups of clouds. The Minor Dark Spot, the second most intense storm observed during Voyager 2's 1989 rendezvous, is further south. Initially, it appeared completely dark, but as you get closer, the bright center of the Minor Dark Spot becomes more visible, as can be seen in most clear high-resolution photographs. Neptune's "dark spots" are believed to be born in the troposphere at lower altitudes than brighter and more visible clouds. Thus, they seem to be a kind of holes in the upper cloud layer. Since these storms are persistent and can exist for several months, they are thought to have an eddy structure. Often associated with dark spots are brighter, persistent clouds of methane that form in the tropopause. The persistence of the accompanying clouds indicates that some of the former "dark spots" may continue to exist as a cyclone even though they lose their dark color. Dark spots can dissipate if they move too close to the equator or through some other as yet unknown mechanism.
internal warmth
The more varied weather on Neptune compared to Uranus is thought to be a consequence of higher internal temperature. At the same time, Neptune is one and a half times more distant from the Sun than Uranus, and receives only 40% of the sunlight that Uranus receives. The surface temperatures of these two planets are approximately equal. Neptune's upper troposphere reaches a very low temperature of -221.4 °C. At a depth where the pressure is 1 bar, the temperature reaches -201.15 °C. Gases go deeper, but the temperature rises steadily. As with Uranus, the heating mechanism is unknown, but the discrepancy is large: Uranus radiates 1.1 times more energy than it receives from the Sun. Neptune radiates 2.61 times more than it receives, its internal heat source produces 161% of that received from the Sun. Despite the fact that Neptune is the most distant planet from the Sun, its internal energy is enough to have the fastest winds in the solar system. Several possible explanations have been proposed, including radiogenic heating by the core of the planet (how the Earth is heated by potassium-40, for example), the dissociation of methane into other chain hydrocarbons under the conditions of Neptune's atmosphere, and convection in the lower atmosphere, which leads to deceleration of gravitational waves above the tropopause.
Education and migration
Simulation of the outer planets and the Kuiper belt: a) Before Jupiter and Saturn entered into a 2:1 resonance; b) Scattering of Kuiper belt objects in the solar system after changing the orbit of Neptune; c) After the ejection of the Kuiper belt bodies by Jupiter.
For the formation of the ice giants - Neptune and Uranus - it has proven difficult to create an accurate model. Modern models It is believed that the density of matter in the outer regions of the solar system was too low for the formation of such large bodies by the traditionally accepted method of matter accretion onto the core. Many hypotheses have been put forward to explain the evolution of Uranus and Neptune.
One of them believes that both ice giants did not form by accretion, but appeared due to instabilities within the primordial protoplanetary disk, and later their atmospheres were "blown away" by radiation from a massive class O or B star.
Another concept is that Uranus and Neptune formed close to the Sun, where the density of matter was higher, and subsequently moved into their current orbits. The Neptune-moving hypothesis is popular because it explains the current resonances in the Kuiper belt, in particular the 2:5 resonance. As Neptune moved outward, it collided with proto-Kuiper belt objects, creating new resonances and chaotically changing existing orbits. It is believed that objects in the scattered disk ended up in their current position due to interactions with resonances created by Neptune's migration.
A 2004 computer model by Alessandro Morbidelli of the Côte d'Azur Observatory in Nice suggested that the movement of Neptune towards the Kuiper belt could be initiated by the formation of a 1:2 resonance in the orbits of Jupiter and Saturn, which served as a kind of gravitational force that pushed Uranus and Neptune into higher orbits and forced them to change location. The expulsion of objects from the Kuiper belt by this migration may also explain the Late Heavy Bombardment, which occurred 600 million years after the formation of the solar system, and the appearance of Trojan asteroids around Jupiter.
Satellites and rings
Neptune currently has 13 known moons. The mass of the largest is more than 99.5% of the total mass of all satellites of Neptune, and only it is massive enough to become spheroidal. This is Triton, discovered by William Lassell just 17 days after the discovery of Neptune. Unlike all other large satellites of the planets in the solar system, Triton has a retrograde orbit. It may have been captured by Neptune's gravity rather than formed in situ, and may have once been a dwarf planet in the Kuiper Belt. It is close enough to Neptune to be constantly in synchronous rotation.
Neptune (top) and Triton (below)
Due to tidal acceleration, Triton slowly spirals towards Neptune, and will eventually be destroyed when the Roche limit is reached, resulting in a ring that may be more powerful than Saturn's (this will happen after a relatively small astronomical scale). time period: 10 to 100 million years). In 1989, Triton estimated the temperature as -235 °C (38 K). At that time, it was the smallest measured value for objects in the solar system with geological activity. Triton is one of the three satellites of the planets in the solar system that have an atmosphere (along with Io and Titan). The existence of a liquid ocean under the ice crust of Triton, similar to the ocean of Europa, is not excluded.
The second (by the time of discovery) known satellite of Neptune is Nereid, an irregularly shaped satellite with one of the highest orbital eccentricities among other satellites of the solar system. An eccentricity of 0.7512 gives it an apoapsis 7 times its periapsis.
Neptune's moon Proteus
From July to September 1989, Voyager 2 discovered 6 new moons of Neptune. Notable among them is Proteus, an irregularly shaped satellite. It is notable for how large a body of its density can be without shrinking into a spherical shape by its own gravity. The second largest moon of Neptune is only a quarter of a percent of the mass of Triton.
The four innermost moons of Neptune are Naiad, Thalassa, Despina, and Galatea. Their orbits are so close to Neptune that they are within its rings. Next to them, Larissa, was originally discovered in 1981 while occulting a star. At first, the occultation was attributed to arcs of the rings, but when Voyager 2 visited Neptune in 1989, it was revealed that the occultation was produced by a satellite. Between 2002 and 2003, 5 more irregular moons of Neptune were discovered, which was announced in 2004. Because Neptune was the Roman god of the seas, his moons are named after lesser sea deities.
Rings
Neptune's rings as seen by Voyager 2
Neptune has a ring system, although much less significant than, for example, Saturn. The rings may be composed of ice particles coated with silicates or a carbon-based material, most likely giving them a reddish tint. The ring system of Neptune includes 5 components.
[edit] Observations
Neptune is not visible to the naked eye, as its magnitude is between +7.7 and +8.0. Thus, the Galilean satellites of Jupiter, the dwarf planet Ceres and the asteroids 4 Vesta, 2 Pallas, 7 Iris, 3 Juno and 6 Hebe are brighter than it in the sky. For confident observation of the planet, you need a telescope with a magnification of 200 or more and a diameter of at least 200-250 mm. In this case, you can see Neptune as a small bluish disk, similar to Uranus. With 7-50 binoculars, it can be seen as a faint star.
Due to the significant distance between Neptune and the Earth, the angular diameter of the planet varies only within 2.2-2.4 arc seconds. This is smallest value among the rest of the planets of the solar system, so visual observation of the details of the surface of this planet is difficult. Therefore, the accuracy of most telescopic data on Neptune was not high until the advent of the Hubble Space Telescope and large ground-based adaptive optics telescopes. In 1977, for example, even the rotation period of Neptune was not reliably known.
For an earthly observer, every 367 days Neptune enters into an apparent retrograde movement, thus forming peculiar imaginary loops in the background of the stars during each opposition. In April and July 2010, and in October and November 2011, these orbital loops will bring it close to where it was discovered in 1846.
Observations of Neptune in the radio wave range show that the planet is a source of continuous radiation and irregular flashes. Both are explained by the rotating magnetic field of the planet. In the infrared part of the spectrum, against a colder background, disturbances in the depths of Neptune's atmosphere (the so-called "storms"), generated by heat from the contracting core, are clearly visible. Observations make it possible to establish their shape and size with a high degree of certainty, as well as to track their movements.
Research
Image of Triton from Voyager 2
Voyager 2 made its closest approach to Neptune on August 25, 1989. Since Neptune was the last major planet that a spacecraft could visit, it was decided to make a close flyby near Triton, regardless of the consequences for the flight path. A similar task was faced by Voyager 1 - a flyby near Saturn and its largest satellite, Titan. Images of Neptune transmitted to Earth by Voyager 2 became the basis for a 1989 appearance on the Public Broadcasting Service (PBS) of an all-night program called Neptune All Night.
During the rendezvous, the signals from the apparatus went to the Earth for 246 minutes. So, for the most part, the Voyager 2 mission relied on preloaded Neptune and Triton rendezvous commands rather than commands from Earth. Voyager 2 made a fairly close pass near the Nereid before passing just 4,400 km from Neptune's atmosphere on August 25. Later that day, Voyager flew past Triton.
Voyager 2 confirmed the existence of the planet's magnetic field and found that it is tilted, like the field of Uranus. The question of the planet's rotation period was solved by measuring radio emission. Voyager 2 also showed Neptune's unusually active weather system. 6 new satellites of the planet and rings were discovered, of which, as it turned out, there were several.
Around 2016, NASA planned to send the Neptune Orbiter to Neptune. Currently, no estimated launch dates have been announced, and the strategic plan for the exploration of the solar system no longer includes this device.
Neptune compared to our planet
To really understand how big Neptune is, in fact, it can be compared with another planet, for convenience, we can take our planet for these purposes.
Comparison of the sizes of the Earth and Neptune
First, let's look at the sizes of the planets being compared. The diameter of the gas giant is about 49,500 km. This makes it the fourth largest planet in the solar system. Compared to our planet, it is 3.9 times larger.
Its mass is 1.02 x 10 * 26 kg. It turns out that it is 17 times larger in mass than our home planet.
How about volume? Its volume is 6.3 x 10 * 13 km 3. We could put 57 planets like ours inside it and still have room. Our day lasts 24 hours, and the day on the gas giant is 16 hours and 6 minutes. A year respectively lasts 164.79 years.
Many parameters of our planets vary greatly, with the exception of perhaps one, this is the force of attraction.
Gravity on Neptune (assuming the planet has a hypothetical surface) is only 14% stronger than gravity on Earth.
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