Neptune was discovered based on theoretical calculations. The fact is that Uranus deviates from the calculated orbit, as if it is being attracted by another planet.
British mathematicians and astronomers John Couch Adams(1819-1892) and James Challis in 1845 made a calculation of 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 new planet. Neptune was first seen by astronomers on September 23, 1846, not far from the positions that were independently predicted by the Englishman Adams and the Frenchman Le Verrier.
Neptune is significantly distant from the Sun.
General characteristics of the planet Neptune
The mass of the planet is 17 times more mass Earth. The radius of the planet is about four Earth radii. Density - The density of the Earth.
Rings have been discovered around Neptune. They are open (broken), that is, 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 that of Uranus.
In contrast, , and Neptune may not have a clear internal stratification. But, most likely, Neptune has a small solid core, equal in mass to the Earth. Neptune's atmosphere is mostly hydrogen and helium with a small amount of methane (1%). Neptune's blue color results from the absorption of red light in the atmosphere by this gas - just like on Uranus.
The planet has a thunderous atmosphere, thin porous clouds composed of frozen methane. The temperature of Neptune's atmosphere is higher than that of Uranus, therefore about 80% H 2
Rice. 1. Composition of Neptune's atmosphere
Neptune has its own internal heat source - it emits 2.7 times more energy than it receives from the Sun. The average surface temperature of the planet is 235 °C. Neptune experiences 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. The winds blow on Neptune in a westerly direction, against the planet's rotation.
There are mountain ranges and cracks on the surface. In winter there is nitrogen snow, and in summer fountains break through the cracks.
The Voyager 2 probe discovered powerful cyclones on Neptune, in which wind speeds reach the speed of sound.
The planet's satellites are named 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.
Neptune's largest satellite is Triton. It was opened in 1846 by William Lassell. Triton is larger than the Moon. Almost all the mass of Neptune's satellite system is concentrated in Triton. It has a high density: 2 g/cm 3 .
Although, of course, the word “giant” will be a little strong in relation to Neptune, a planet that, although very large by cosmic standards, is, nevertheless, significantly inferior in size to our other giant planets: Saturn, Saturn, etc. Speaking of Uranus, although this planet is larger in size than Neptune, Neptune is still 18% larger in mass than Uranus. In general, this planet, named because of its blue color To honor the ancient god of the seas, Neptune can be considered the smallest of the giant planets and at the same time the most massive - Neptune’s density is many times stronger than that of other planets. But compared to Neptune and our Earth, they are tiny, if you imagine that our Sun is the size of a door, then the Earth is the size of a coin, and Neptune is the same in size as a large baseball.
The history of the discovery of the planet Neptune
The history of the discovery of Neptune is unique in its kind, since it is the first planet in our solar system that was discovered purely theoretically, thanks to mathematical calculations, and only then was it noticed through a telescope. It happened like this: back in 1846, French astronomer Alexis Bouvard observed the movement of the planet Uranus through a telescope and noticed strange deviations in its orbit. The anomaly in the movement of the planet, in his opinion, could be caused by the strong gravitational influence of some other large celestial body. Alexis’s German colleague, astronomer Johann Halle, made the necessary mathematical calculations to determine the location of this previously unknown planet, and they turned out to be correct - soon our Neptune was discovered at the site of the supposed location of the unknown “Planet X”.
Although long before this, the planet Neptune was observed in a telescope by the great. True, in his astronomical notes he noted it as a star, not a planet, so the discovery was not credited to him.
Neptune is the most distant planet in the solar system
“But what about?”, you probably ask. In fact, everything here is not as simple as it seems at first glance. Since its discovery in 1846, Neptune has rightfully been considered the farthest planet from the Sun. But in 1930, little Pluto was discovered, which is even further away. There’s just one nuance here: Pluto’s orbit is strongly elongated along an ellipse in such a way that at certain moments of its movement Pluto is closer to the Sun than Neptune. Last time A similar astronomical phenomenon occurred from 1978 to 1999 - within 20 years, Neptune again had the title of the full-fledged “farthest planet from the Sun.”
Some astronomers, in order to get rid of these confusions, even proposed to “demote” Pluto from the title of planet, they say, it’s just a small heavenly body, flying in orbit, or assign the status of a “dwarf planet”, however, disputes on this matter are still ongoing.
Features of the planet Neptune
Neptune has its bright blue appearance due to the strong density of clouds in the planet’s atmosphere; these clouds conceal within themselves still completely unknown to our science chemical compounds, which turn blue when absorbed from sunlight. One year on Neptune is equal to our 165 years; it is during this time that Neptune completes its full cycle in its orbit around the Sun. But a day on Neptune is not as long as a year; it is even shorter than ours on Earth, since it lasts only 16 hours.
Neptune temperature
Because Sun rays they reach the distant “blue giant” in very small quantities, it is natural that on its surface it is very, very cold - average temperature the surface there is -221 degrees Celsius, which is two times lower than the freezing point of water. In a word, if you were on Neptune, you would turn into ice in the blink of an eye.
Surface of Neptune
Neptune's surface consists of ammonia and methane ice, but the planet's core may well turn out to be rock, but this is still just a hypothesis. It is curious that the force of gravity on Neptune is very similar to that of Earth, it is only 17% greater than ours, and this despite the fact that Neptune is 17 times larger than Earth. Despite this, we are unlikely to be able to walk around Neptune in the near future, see the previous paragraph about the ice. And besides, strong winds blow on the surface of Neptune, the speed of which can reach up to 2400 kilometers per hour (!), perhaps on no other planet in our solar system there are such strong winds as here.
Neptune size
As mentioned above, it is 17 times larger than our Earth. The picture below shows a comparison of the sizes of our planets.
Atmosphere of Neptune
The composition of Neptune's atmosphere is similar to the atmospheres of most similar giant planets: it is mainly dominated by hydrogen and helium atoms, and also contains small amounts of ammonia, frozen water, methane and other chemical elements. But unlike others major planets Neptune's atmosphere contains a lot of ice, due to its remote location.
Rings of the planet Neptune
Surely when you hear about planetary rings, Saturn immediately comes to mind, but in fact, it is far from the only owner of rings. Our Neptune also has rings, although not as large and beautiful as those of the planet. Neptune has five rings in total, named after the astronomers who discovered them: Halle, Le Verrier, Lascelles, Arago and Adams.
Neptune's rings consist of small pebbles and cosmic dust (many micron-sized particles), their structure is somewhat similar to the rings of Jupiter and they are quite difficult to notice, since they are black. Scientists believe that Neptune's rings are relatively young, at least much younger than the rings of its neighbor Uranus.
Moons of Neptune
Neptune, like any decent giant planet, has its own satellites, not just one, but thirteen, named after the smaller sea gods of the ancient pantheon.
Particularly interesting is the satellite Triton, discovered, in part, thanks to... beer. The fact is that the English astronomer William Lasing, who actually discovered Triton, made a large fortune by brewing and trading beer, which subsequently allowed him to invest a lot of money and time in his favorite hobby - astronomy (especially since it is not cheap to equip a high-quality observatory).
But what is interesting and unique about Triton? The fact is that this is the only known satellite in our solar system that rotates around the planet in the opposite direction relative to the rotation of the planet itself. In scientific terminology, this is called “retrograde orbit.” Scientists suggest that Triton was not previously a satellite at all, but an independent dwarf planet (like Pluto), which, by the will of fate, fell into the sphere of influence of Neptune’s gravity, essentially captured by the “blue giant.” But it doesn't end there: Neptune's gravity pulls Triton closer and closer, and after several million light years, gravitational forces can tear the satellite apart.
How long does it take to fly to Neptune?
For a long time. This is in short, with modern technology, of course. After all, the distance from Neptune to the Sun is 4.5 billion kilometers, and the distance from Earth to Neptune is 4.3 billion kilometers, respectively. The only satellite sent from Earth to Neptune, Voyager 2, launched in 1977, reached its destination only in 1989, where it photographed the “large dark spot” on the surface of Neptune and observed a number of powerful storms in the planet’s atmosphere.
Planet Neptune video
And at the end of our article we offer you interesting video about the planet Neptune.
- Neptune is the eighth and farthest planet from the Sun. The ice giant is located at a distance of 4.5 billion km, which is 30.07 AU.
- A day on Neptune (a full revolution around its axis) is 15 hours 58 minutes.
- The period of revolution around the Sun (Neptunian year) lasts about 165 Earth years.
- Neptune's surface is covered by a huge, deep ocean of water and liquefied gases, including methane. Neptune is blue, like our Earth. This is the color of methane, which absorbs the red part of the sunlight spectrum and reflects the blue.
- The planet's atmosphere consists of hydrogen with a small admixture of helium and methane. The temperature of the upper edge of the clouds is -210 °C.
- Even though Neptune is the farthest planet from the Sun, it internal energy enough to have the fastest winds in the solar system. In the atmosphere of Neptune the most raging strong winds among the planets solar system
- , according to some estimates, their speeds can reach 2100 km/h There are 14 satellites orbiting Neptune. which were named after various gods and nymphs of the sea in Greek mythology
- . The largest of them, Triton, has a diameter of 2700 km and rotates in the opposite direction of rotation of the other satellites of Neptune.
- Neptune has 6 rings.
- There is no life on Neptune as we know it.
Neptune was the last planet visited by Voyager 2 on its 12-year journey through the solar system. Launched in 1977, Voyager 2 passed within 5,000 km of Neptune's surface in 1989. The earth was more than 4 billion km from the event site; The radio signal with information traveled to Earth for more than 4 hours. Neptune
Neptune is the eighth planet from the Sun and the most distant planet in the Solar System. It is a gas giant and a representative of the category of solar planets of the outer system. Pluto has dropped out of the planetary list, so Neptune closes the chain.
It cannot be found without instruments, so it was found relatively recently. The close approach was observed only once during the flyby of Voyager 2 in 1989. Let's find out what planet Neptune is in interesting facts.
Interesting facts about the planet Neptune
The ancients did not know about him
- Neptune cannot be found without the use of instruments. It was first noticed only in 1846. The position was calculated mathematically. The name is given in honor of the sea deity of the Romans.
Rotates rapidly on an axis
- Equatorial clouds complete a revolution in 18 hours.
Smallest among the ice giants
- It is smaller than Uranus, but superior in mass. Under the heavy atmosphere are layers of hydrogen, helium and methane gases. There is water, ammonia and methane ice. The inner core is represented by rock.
The atmosphere is filled with hydrogen, helium and methane
- Neptune's methane absorbs red light, which is why the planet appears blue. High clouds are constantly drifting.
Active climate
- It is worth noting large storms and powerful winds. One of the large-scale storms was recorded in 1989 - the Great Dark Spot, which lasted 5 years.
There are thin rings
- They are represented by ice particles mixed with dust grains and carbon-containing matter.
There are 14 satellites
- Neptune's most interesting satellite is Triton, a frosty world that releases particles of nitrogen and dust from beneath the surface. Can be pulled by planetary gravity.
Sent one mission
- In 1989, Voyager 2 flew past Neptune, sending back the first large-scale images of the system. The planet was also observed by the Hubble telescope.
Size, mass and orbit of the planet Neptune
With a radius of 24,622 km, it is the fourth largest planet, four times larger than ours. With a mass of 1.0243 x 10 26 kg, it outpaces us 17 times. The eccentricity is only 0.0086, and the distance from the Sun to Neptune is 29.81 AU. in an approximate state and 30.33. a.e. at maximum.
| Polar compression | 0,0171 |
|---|---|
| Equatorial | 24 764 |
| Polar radius | 24,341 ± 30 km |
| Surface area | 7.6408 10 9 km² |
| Volume | 6.254 10 13 km³ |
| Weight | 1.0243 10 26 kg |
| Average density | 1.638 g/cm³ |
| Acceleration free falls at the equator |
11.15 m/s² |
| Second space speed |
23.5 km/s |
| Equatorial speed rotation |
2.68 km/s 9648 km/h |
| Rotation period | 0.6653 days 15 h 57 min 59 s |
| Axis tilt | 28.32° |
| Right ascension north pole |
19h 57m 20s |
| North pole declination | 42.950° |
| Albedo | 0.29 (Bond) 0.41 (geom.) |
| Apparent magnitude | 8.0-7.78 m |
| Angular diameter | 2,2"-2,4" |
A sidereal revolution takes 16 hours, 6 minutes and 36 seconds, and an orbital passage takes 164.8 years. Neptune's axial tilt is 28.32° and is similar to Earth's, so the planet goes through similar seasonal changes. But if we add the factor of a long orbit, we get a season with a duration of 40 years.
Neptune's planetary orbit influences the Kuiper Belt. Due to the planet's gravity, some objects become unstable and create gaps in the belt. In some empty areas there is an orbital path. Resonance with bodies – 2:3. That is, the bodies complete 2 orbital passages for every 3 at Neptune.
The ice giant has Trojan bodies located at the Lagrange points L4 and L5. Some even amaze with their stability. Most likely, they were simply created nearby, and were not attracted gravitationally later.
Composition and surface of the planet Neptune
This type of object is called ice giants. There is a rocky core (metals and silicates), a mantle made of water, methane ice, ammonia and a hydrogen, helium and methane atmosphere. The detailed structure of Neptune is visible in the figure.
The core contains nickel, iron and silicates, and its mass is 1.2 times greater than ours. The central pressure rises to 7 Mbar, which is twice ours. The situation is heating up to 5400 K. At a depth of 7000 km, methane is transformed into diamond crystals, which fall down in the form of hail.
The mantle reaches 10-15 times the mass of the earth and is filled with ammonia, methane and water mixture. The substance is called icy, although in reality it is a dense, hot liquid. The atmospheric layer extends 10-20% from the center.
In the lower atmospheric layers, you can see how methane, water and ammonia concentrations increase.
Moons of the planet Neptune
Neptune's lunar family is represented by 14 satellites, where all but one have names in honor of Greek and Roman mythology. They are divided into 2 classes: regular and irregular. The first are Naiad, Thalassa, Despina, Galatea, Larissa, S/2004 N 1 and Proteus. They are located closest to the planet and march in circular orbits.
The satellites range from 48,227 km to 117,646 km from the planet, and all except S/2004 N 1 and Proteus orbit the planet in less than its orbital period (0.6713 days). According to parameters: 96 x 60 x 52 km and 1.9 × 10 17 kg (Naiad) to 436 x 416 x 402 km and 5.035 × 10 17 kg (Proteus).
All satellites, except Proteus and Larissa, are elongated in shape. Spectral analysis shows that they formed from water ice mixed with dark material.
The irregular ones follow inclined eccentric or retrograde orbits and live at great distances. The exception is Triton, which orbits Neptune in a circular orbital path.
In the list of irregulars one can find Triton, Nereids, Halimeda, Sao, Laomedea, Neso and Psamatha. In terms of size and mass, they are practically stable: from 40 km in diameter and 1.5 × 10 16 kg in mass (Psamapha) to 62 km and 9 x 10 16 kg (Halimeda).
Triton and the Nereids are considered separately because they are the largest irregular moons in the system. Triton contains 99.5% of Neptune's orbital mass.
They rotate close to the planet and have unusual eccentricities: Triton has almost perfect circle, and Nereid’s is the most eccentric.
Neptune's largest satellite is Triton. Its diameter covers 2700 km, and its mass is 2.1 x 10 22 kg. Its size is sufficient to achieve hydrostatic balance. Triton moves along a retrograde and quasi-circular path. It is filled with nitrogen, carbon dioxide, methane and water ice. Albedo is more than 70%, therefore it is considered one of the brightest objects. The surface appears reddish. It is also surprising because it has its own atmospheric layer.
The density of the satellite is 2 g/cm 3, which means 2/3 of the mass is given to rocks. Liquid water and an underground ocean may also be present. In the south there is a large polar cap, ancient crater scars, canyons and ledges.
It is believed that Triton was attracted by gravity and was previously considered part of the Kuiper belt. Tidal attraction leads to convergence. A collision between the planet and the satellite may occur in 3.6 billion years.
Nereid is the third largest in the lunar family. Rotates in a prograde but extremely eccentric orbit. The spectroscope found ice on the surface. Perhaps it is the chaotic rotation and elongated shape that lead to irregular changes in apparent magnitude.
Atmosphere and temperature of the planet Neptune
At its higher elevation, Neptune's atmosphere consists of hydrogen (80%) and helium (19%) with minor methane traces. The blue tint occurs because methane absorbs red light. The atmosphere is divided into two main spheres: the troposphere and the stratosphere. Between them there is a tropopause with a pressure of 0.1 bar.
Spectral analysis shows that the stratosphere is hazy due to the accumulation of mixtures created by the contact of UV rays and methane. It contains carbon monoxide and hydrogen cyanide.
So far, no one can explain why the thermosphere is heated to 476.85°C. Neptune is extremely far from the star, so a different heating mechanism is needed. This could be the contact of the atmosphere with ions in the magnetic field or gravitational waves of the planet itself.
Neptune does not have a solid surface, so the atmosphere rotates differentially. The equatorial part rotates with a period of 18 hours, the magnetic field - 16.1 hours, and the polar zone - 12 hours. This is why strong winds occur. Three large-scale ones were recorded by Voyager 2 in 1989.
The first storm extended over 13,000 x 6,600 km and looked like Jupiter's Great Red Spot. In 1994, the Hubble telescope tried to find the Great Dark Spot, but it was not there. But a new one has formed on the territory of the northern hemisphere.
Scooter is another storm represented by light cloud cover. They are located south of the Great Dark Spot. In 1989, the Little Dark Spot was also noticed. At first it seemed completely dark, but when the device got closer, it was possible to detect a bright core.
Rings of the planet Neptune
The planet Neptune has 5 rings named after scientists: Halle, Le Verrier, Lascelles, Arago and Adams. They are represented by dust (20%) and small fragments of rock. They are difficult to find because they lack brightness and differ in size and density.
Johann Halle was the first to examine the planet with a magnifying instrument. The ring comes first and is 41,000-43,000 km away from Neptune. Le Verrier is only 113 km wide.
At a distance of 53200-57200 km with a width of 4000 km there is the Lascelles Ring. This is the widest ring. The scientist found Triton 17 days after the discovery of the planet.
The Arago ring, located 57,200 km, extends for 100 km. François Arago mentored Le Verrier and was active in the planet debate.
Adams is only 35 km wide. But this ring is Neptune's brightest and is easy to find. It has five arcs, three of which are called Freedom, Equality, Brotherhood. It is believed that the arcs were gravitationally captured by Galatea, located inside the ring. Take a look at the photo of Neptune's rings.
The rings are dark and created from organic compounds. Holds a lot of dust. It is believed that these are young formations.
History of the study of the planet Neptune
Neptune was not recorded until the 19th century. Although, if you carefully examine Galileo’s sketches from 1612, you will notice that the dots point to the location of the ice giant. So before, the planet was simply mistaken for a star.
In 1821, Alexis Bouvard produced diagrams showing the orbital path of Uranus. But further review showed deviations from the drawing, so the scientist thought that there was a large body nearby influencing the path.
John Adams began a detailed study of the orbital passage of Uranus in 1843. Regardless of him in 1845-1846. Urbe Le Verrier worked. He shared his knowledge with Johann Halle at the Berlin Observatory. The latter confirmed that there was something big nearby.
The discovery of the planet Neptune caused much controversy regarding its discoverer. But scientific world acknowledged the merits of Le Verrier and Adams. But in 1998 it was considered that the first one had done more.
At first, Le Verrier proposed naming the object in his honor, which caused a lot of indignation. But his second proposal (Neptune) became modern name. The fact is that it fit into the traditions of the name. Below is a map of Neptune.
Map of the surface of the planet Neptune
Click on the image to enlarge it
Neptune is the eighth and outermost planet in the solar system. Neptune is also the fourth largest planet in diameter and third largest in mass. The mass of Neptune is 17.2 times, and the diameter of the equator is 3.9 times greater than 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 became the first planet 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 disturbing influence of which caused them. Neptune was found within its predicted position. Soon its satellite Triton was discovered, but the remaining 12 satellites known today were unknown until the 20th century. Neptune has only been visited by one spacecraft, Voyager 2, which flew close to the planet on August 25, 1989.
Neptune is similar 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, consists primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but contains a higher proportion of ices: water, ammonia, and methane. Neptune's core, like Uranus, consists mainly of ice and rock. Traces of methane in the outer layers of the atmosphere, in particular, are the cause of blue color planets.
Neptune's atmosphere is home to the strongest winds of any planet in the solar system; according to some estimates, their speeds can reach 2,100 km/h. During the flyby of Voyager 2 in 1989, the so-called Great Dark Spot, similar to the Great Red Spot on Jupiter, was discovered in the southern hemisphere of Neptune. Neptune's temperature in upper layers atmosphere is close to -220 °C. At the center of Neptune, the temperature ranges, according to 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 only reliably confirmed by Voyager 2 in 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 its discovery, Neptune was designated simply as the "planet outer of Uranus" or as "Le Verrier's planet." The first to put forward the idea of an official name was Halle, 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 calling 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 his own name, Le Verrier, and was supported by the observatory's director, François Arago, but the initiative met with significant opposition outside France. French almanacs very quickly returned the name Herschel for Uranus, in honor of its discoverer William Herschel, and Le Verrier for the new planet.
The director of the Pulkovo Observatory, Vasily Struve, preferred the name “Neptune”. He reported the reasons for his choice at the congress of the Imperial Academy of Sciences in St. Petersburg on December 29, 1846. This name gained 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 remained the farthest known planet from the Sun. After the discovery of Pluto, Neptune became the penultimate planet, with the exception of 1979-1999, when Pluto was within Neptune's orbit. However, the study of the Kuiper Belt in 1992 led many astronomers to debate whether Pluto should be considered 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, the average distance from the Sun, and the inclination of the equator to the orbital plane were known relatively accurately, there were also parameters measured less accurately. In particular, the mass was estimated at 17.26 Earth's instead of 17.15; equatorial radius is 3.89 instead of 3.88 from Earth. The sidereal period of revolution 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 the knowledge of that time.
In some points there were discrepancies later. Initially, before the Voyager 2 flight, it was assumed that Neptune's magnetic field had the same configuration as the field of Earth or Saturn. According to the latest ideas, Neptune's field has the form of the so-called. "inclined rotator". The geographic and magnetic “poles” of Neptune (if we imagine 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.
physical characteristics
Comparison of the sizes of 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 Earth, but is only 1/19 of the mass of Jupiter. Neptune's equatorial radius is 24,764 km, which is almost 4 times that of Earth. Neptune and Uranus are often considered a subclass of gas giants called "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 similar masses are often called “Neptunes,” and astronomers also often use Jupiter (“Jupiters”) as a metonym.
Orbit and rotation
During one full 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 distance between the Sun and Earth, or 30.1 AU), and it takes 164.79 years to complete a revolution around the Sun. The distance between Neptune and Earth is between 4.3 and 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 Neptune's revolution. The planet's elliptical orbit is inclined 1.77° relative to 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. Because Neptune does not have a solid surface, its atmosphere is subject to differential rotation. The broad equatorial zone rotates with a period of approximately 18 hours, which is slower than the 16.1 hour rotation magnetic field planets. In contrast to the equator, the polar regions rotate every 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), the "classical belt", with orbits not significantly influenced by Neptune, and 1:2 resonance (Tutino)
Neptune has a great influence on the Kuiper Belt, which is very distant from it. The Kuiper Belt is a ring of icy small planets, similar to the asteroid belt between Mars and Jupiter, but much more extensive. It ranges from the orbit of Neptune (30 AU) to 55 astronomical units from the sun. The gravitational force of Neptune has the most significant effect on the Kuiper cloud (including in terms of the formation of its structure), comparable in proportion to the influence of Jupiter’s gravity 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 appeared in the structure of the belt. An example is the area between 40 and 42 a. e.
The orbits of objects that can be held in this belt for a sufficiently long time are determined by the so-called. age-old 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 orbital period of an object around the Sun is related to the orbital period of Neptune as small integers, for example, 1:2 or 3:4. In this way, the objects mutually stabilize their orbits. If, for example, an object orbits the Sun twice as fast as Neptune, it will travel exactly halfway, while Neptune will return to its original position.
The most densely populated part of the Kuiper belt, which includes more than 200 known objects, is in a 2:3 resonance with Neptune]. These objects make one revolution every 1? orbits of Neptune and are known as “plutinos” because among them is one of the largest Kuiper Belt objects, 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 resonances of 3:4, 3:5, 4:7 and 2:5. At its Lagrange points (L4 and L5), zones of gravitational stability, Neptune holds many Trojan asteroids, as if dragging them along in orbit. Neptune's Trojans are in a 1:1 resonance with him. The 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 planet's total mass, 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.
Internal structure of Neptune:
1. Upper atmosphere, upper clouds
2. An atmosphere consisting of hydrogen, helium and methane
3. A mantle made of water, ammonia and methane ice
4. Rock-ice core
Gradually, this darker and hotter region compacts into a superheated liquid mantle, where temperatures reach 2000-5000 K. The mass of Neptune's mantle is 10-15 times greater than that of Earth, according to various estimates, and is rich in water, ammonia, methane and other compounds. According to the generally accepted terminology in planetary science, this matter is called icy, even though it is a hot, very dense liquid. This highly conductive liquid is sometimes called an ocean of aqueous ammonia. At a depth of 7,000 km, conditions are such that methane decomposes into diamond crystals, which “fall” onto the core. According to one hypothesis, there is an entire 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 with its magnetosphere and magnetic field, strongly inclined at 47° relative to the planet's rotation axis, and extending out 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 "sideways rotation." However, now, after comparing the magnetic fields of these two planets, scientists believe that this strange orientation of the magnetosphere in space may be caused by tides in the inner regions. Such a field can appear due to convective movements of liquid in a thin spherical layer of electrically conductive liquids of these two planets (a supposed combination of ammonia, methane and water), which drives a hydromagnetic dynamo. The magnetic field on Neptune's equatorial surface is estimated to be 1.42 T during 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 the dipole moment. In contrast, the Earth, Jupiter and Saturn have a relatively small quadrupole moment, and their fields are less deviated from the polar axis. Neptune's bow shock, where the magnetosphere begins to slow the solar wind, passes at a distance of 34.9 planetary radii. The magnetopause, where magnetospheric pressure balances the solar wind, is located at a distance of 23-26.5 Neptune radii. The magnetotail extends to approximately 72 Neptune radii, and very likely much further.
Atmosphere
Hydrogen and helium were found in the upper layers of the atmosphere, which account for 80 and 19%, respectively, at a given altitude. Traces of methane are also observed. Noticeable absorption bands of methane 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 its blue tint, although Neptune's bright azure is different from the more moderate aquamarine color of Uranus. Since the methane content of Neptune's atmosphere is not very 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 the blue color. Neptune's atmosphere is divided into 2 main regions: the lower troposphere, where the temperature decreases with altitude, and the stratosphere, where the temperature, on the contrary, increases with altitude. 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 turns into the exosphere. Models of Neptune's troposphere suggest that, depending on altitude, it consists of clouds of varying compositions. Upper-level clouds are in a zone of pressure below one bar, where temperatures favor methane condensation.
The photo taken by Voyager 2 shows the vertical relief of the clouds
At pressures between one and five bars, clouds of ammonia and hydrogen sulfide form. At pressures greater than 5 bars, clouds may consist of ammonia, ammonium sulfide, hydrogen sulfide and water. Deeper down, at a pressure of approximately 50 bar, clouds of water ice can exist at temperatures as low as 0 °C. It is also possible that clouds of ammonia and hydrogen sulfide may be found in this area. Neptune's high-altitude clouds were observed by the shadows they cast on the opaque cloud layer below. Prominent among them are cloud bands that “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. 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 were also found in the stratosphere. Neptune's stratosphere is warmer than Uranus' stratosphere due to its higher concentration of hydrocarbons. For unknown reasons, the planet’s thermosphere has an anomalously high temperature of about 750 K. For such 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 heating mechanism is based on gravity waves from internal regions planets that disperse in the atmosphere. The thermosphere contains traces of carbon monoxide and water that entered it, possibly from external sources such as meteorites and dust.
Climate
One of the differences between Neptune and Uranus is the level of meteorological activity. Voyager 2, which flew near Uranus in 1986, recorded extremely weak atmospheric activity. In contrast to Uranus, Neptune exhibited noticeable weather changes during Voyager 2's 1989 survey.
Large Dark Spot (top), Scooter (white cloud in the middle), and Small Dark Spot (bottom)
The weather on Neptune is extremely dynamic system storms, with winds sometimes reaching supersonic speeds (about 600 m/s). While tracking the movement of permanent clouds, a change in wind speed from 20 m/s to east direction to 325 m/s on the western. In the upper cloud layer, wind speeds vary from 400 m/s along the equator to 250 m/s at the poles. Most winds on Neptune blow in the direction opposite to the planet's rotation on its axis. The general pattern 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 direction air flow, is believed to be a consequence of the “skin effect” rather than any deep atmospheric processes. The content of methane, ethane and acetylene in the atmosphere in the equator region is tens and hundreds of times higher than the content of these substances in the pole region. This observation can be considered evidence in favor of the existence of upwelling at Neptune's equator and its decrease 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, where temperatures average -200 °C. This difference in temperature is enough to allow methane, which is frozen in other areas of Neptune's upper atmosphere, to leak 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 moves through its orbit towards opposite side The south pole will gradually go into shadow, and Neptune will substitute the north pole for the Sun. Thus, the release of methane into space will move from the south pole to the north. Because of seasonal changes cloud bands in Neptune's southern hemisphere have been observed to increase in size and albedo. This trend was noticed back in 1980, and is expected to continue into 2020 with the arrival of a new season on Neptune. The seasons change every 40 years.
Storms
Large dark spot, photo from Voyager 2
In 1989, the Great Dark Spot, a persistent anticyclone storm measuring 13,000 to 6,600 km, was discovered by NASA's Voyager 2 spacecraft. This atmospheric storm resembled Jupiter's Great Red Spot, but on November 2, 1994, the Hubble Space Telescope did not find it in its original location. Instead, a new similar formation was discovered in the northern hemisphere of the planet. Scooter is another storm found south of the Great Dark Spot. Its name is a consequence of the fact that several months before Voyager 2's approach to Neptune, it was clear that this group of clouds was moving much faster than the Great Dark Spot. Subsequent images revealed groups of clouds even faster than the scooter. The Minor Dark Spot, the second most intense storm observed during Voyager 2's approach to the planet in 1989, is located even further south. Initially it appeared completely dark, but as it got closer, the bright center of the Small Dark Spot became more visible, as can be seen in most clear photographs from high resolution. Neptune's "dark spots" are thought to originate in the troposphere at lower altitudes than the brighter, more visible clouds. Thus, they appear to be holes in the upper cloud layer. Because these storms are persistent and can persist for months, they are thought to have a vortex structure. Often associated with dark spots are brighter, persistent clouds of methane that form at the tropopause. The persistence of the accompanying clouds shows that some former "dark spots" may continue to exist as a cyclone, even though they lose their dark color. Dark spots may dissipate if they move too close to the equator or through some other as-yet-unknown mechanism.
The more varied weather on Neptune, compared to Uranus, is believed to be a consequence of higher internal temperatures. At the same time, Neptune is one and a half times farther 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. The upper troposphere of Neptune reaches a very low temperature of -221.4 °C. At a depth where the pressure is 1 bar, the temperature reaches -201.15 °C. The gases go deeper, but the temperature steadily rises. As with Uranus, the heating mechanism is unknown, but the discrepancy is large: Uranus emits 1.1 times more energy than it receives from the Sun. Neptune emits 2.61 times more than it receives, its internal heat source produces 161% of what it receives from the Sun. Despite the fact that Neptune is the farthest planet from the Sun, its internal energy is sufficient to have the fastest winds in the solar system. Several possible explanations have been proposed, including radiogenic heating by the planet's core (as the Earth is heated by potassium-40, for example), the dissociation of methane into other chain hydrocarbons in Neptune's atmosphere, and convection in the lower atmosphere, which leads to the braking of gravitational waves above the tropopause.
Education and migration
Simulation 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 a change in the orbit of Neptune; c) After the ejection of Kuiper belt bodies by Jupiter.
The formation of the ice giants Neptune and Uranus has proven difficult to accurately model. Modern models believe that the density of matter in the outer regions of the solar system was too low for the formation of such large bodies 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 were not formed by accretion, but appeared due to instabilities inside the primordial protoplanetary disk, and later their atmospheres were “blown away” by the radiation of a massive O or B class 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 migration hypothesis is popular because it helps explain current resonances in the Kuiper Belt, particularly the 2:5 resonance. As Neptune moved outward, it collided with proto-Kuiper belt objects, creating new resonances and chaotically changing existing orbits. Scattered disk objects are thought to be in their current positions due to interactions with resonances created by Neptune's migration.
Proposed in 2004 computer model Alessandro Morbidelli from the Côte d'Azur Observatory in Nice suggested that Neptune's movement into the Kuiper Belt could have been 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 change their location. The pushing of objects out of the Kuiper Belt as a result of this migration may also explain the Late Heavy Bombardment that occurred 600 million years after the formation of the Solar System and the appearance of Trojan asteroids near Jupiter.
Satellites and rings
At Neptune's this moment 13 satellites are known. The mass of the largest is more than 99.5% of the total mass of all Neptune's moons, 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 the 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 that it is constantly in synchronous rotation.
Neptune (above) and Triton (below)
Due to tidal acceleration, Triton slowly spirals toward Neptune, and will eventually be destroyed when it reaches the Roche limit, resulting in a ring that may be more powerful than Saturn's rings (this will happen in a relatively short time on astronomical scales). time period: 10 to 100 million years). In 1989, Triton's temperature estimate was -235 °C (38 K). At that time, this was the smallest measured value for objects in the Solar System with geological activity. Triton is one of the three satellites of the solar system planets that have an atmosphere (along with Io and Titan). It is possible that a liquid ocean similar to Europa’s ocean exists under Triton’s icy crust.
The second (by time of discovery) known satellite of Neptune is Nereid, a satellite irregular shape with one of the highest orbital eccentricities among other satellites in the Solar System. An eccentricity of 0.7512 gives it an apoapse 7 times larger than its periapse.
Neptune's moon Proteus
From July to September 1989, Voyager 2 discovered 6 new satellites of Neptune. Notable among them is the irregularly shaped satellite Proteus. It is remarkable for how large a body of its density can be without being pulled into a spherical shape by its own gravity. Neptune's second-most massive moon is only a quarter of a percent of Triton's mass.
Neptune's four innermost satellites are Naiad, Thalassa, Despina and Galatea. Their orbits are so close to Neptune that they are within its rings. The next one, Larissa, was originally discovered in 1981 during the occultation of a star. The occultation was initially attributed to ring arcs, but when Voyager 2 visited Neptune in 1989, it was discovered that the occultation was produced by a satellite. Between 2002 and 2003, 5 more irregular moons of Neptune were discovered, which were announced in 2004. Because Neptune was the Roman god of the seas, his moons are named after lesser sea deities.
Rings
Neptune's rings captured by Voyager 2
Neptune has a ring system, although much less significant than, for example, Saturn. The rings may be composed of icy particles coated with silicates, or a carbon-based material, which is most likely what gives them their reddish hue. Neptune's ring system has 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. To confidently observe the planet, you need a telescope with a magnification of 200 or higher 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 Earth, the angular diameter of the planet varies only within 2.2-2.4 arcseconds. This is the smallest value among the other planets in the Solar System, so visual observation of the surface details of this planet is difficult. Therefore, the accuracy of most telescopic data on Neptune was poor until the advent of the Hubble Space Telescope and large ground-based adaptive optics telescopes. In 1977, for example, even Neptune’s rotation period was not reliably known.
To an observer on Earth, every 367 days Neptune enters an apparent retrograde motion, thus forming peculiar imaginary loops against the background of stars during each opposition. In April and July 2010 and October and November 2011, these orbital loops will bring it close to the coordinates where it was discovered in 1846.
Observations of Neptune at radio waves show that the planet is a source of continuous radiation and irregular flares. Both are explained by the planet's rotating magnetic field. 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 the heat from the contracting core, are clearly visible. Observations make it possible to establish with a high degree of certainty their shape and size, as well as track their movements.
Research
Voyager 2 image of Triton
Voyager 2 came closest to Neptune on August 25, 1989. Since Neptune was the last major planet that could be visited spacecraft, 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 an all-night program on the Public Broadcasting Service (PBS) in 1989 called Neptune All Night.
During the approach, signals from the device traveled to Earth for 246 minutes. Therefore, for the most part, the Voyager 2 mission relied on preloaded commands to approach Neptune and Triton rather than commands from Earth. Voyager 2 made a fairly close pass of Nereid before passing just 4,400 km from Neptune's atmosphere on August 25. Later that day, Voyager flew close to Triton.
Voyager 2 confirmed the existence of the planet's magnetic field and found that it is tilted, like Uranus's field. The question of the planet's rotation period was resolved by measuring radio emission. Voyager 2 also revealed 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 spacecraft to Neptune. Currently, no estimated launch dates have been announced, and the strategic plan for exploring the Solar System no longer includes this device.