Triton and Nereid satellite of Neptune. Mysterious triton and nereid - satellites of the planet Neptune

It was discovered by the English astronomer William Lassell in 1846, 17 days after the discovery of the planet. Was named Triton- in honor of the Greek god of the deep sea only in 1880. In the middle of the twentieth century, the third largest small moon of Neptune was discovered - Nereid. Its radius is only 170 km, and the period of revolution around the planet almost corresponds to one Earth year - 360 days. third satellite, Larissa, was discovered by a group of scientists: Harold Reitsem, William Hubbard, Larry Lebofsky, David Tholen, on May 24, 1981, when he was just passing through the disk of a bright star. Larissa is located at a distance of 73.55 thousand km from the center of the planet, which makes it the fifth satellite in terms of distance from Neptune. The satellite has an irregular, non-spherical shape with a large number of impact craters on the surface. The fate of Larissa is such that in about 10-20 million years, the satellite's orbit, under the influence of tidal and gravitational forces, will approach Neptune to such an extent that it will be completely absorbed and destroyed by it, and the remaining fragments from the satellite will become part of the planet and Neptune's rings.

Five more moons: Proteus, Galatea, Despina, Thalassa and Naiad were discovered by Voyager 2 in 1989. The largest of them Proteus, as well as the second largest satellite of Neptune - an irregularly shaped body with an average diameter of 420 km. Despina and Galatea circulate at distances of 62,000 km and 52,000 km over an orbital period of 8.03 hours and 10.3 hours, respectively. The remaining satellites of Neptune were discovered not by space interplanetary vehicles, but in special astronomical observatories using ground-based telescopes in 02-03 years of the 21st century. All of them are very far from Neptune and the distance is measured in millions of kilometers. For example, the nearest of the outer satellites is located at a distance of 15.7 million km, and the Neso satellite is located 48.3 million kilometers from the upper atmosphere of Neptune.

Triton

Satellite name: Triton;

Diameter: 2,707 km;

Pov area: 23,018,000 km²;

Volume: 10.38×10 9 km³;

Weight: 2.14×1022 kg;

Density be: 2060 kg/m³;

Rotation period: 5.88 days;

Period of circulation: 5.88 days;

Distance from Neptune: 330,000 km;

Orbital speed: 4.39 km/s;

equator length: 8,500 km;

Orbital inclination: 157°;

Accel. free fall: 0.78 m/s²;

Triton, Neptune's largest moon, was discovered by English astronomer William Lassell in 1846, just 17 days after the planet's discovery. In ancient Greek mythology, Triton corresponds to the son of Neptune and Salacia, as well as the god and messenger of the deep sea. Triton is the seventh largest satellite in the solar system, its diameter is about 2,700 km, thus it is inferior to Io, Europa, Ganymede, Callisto, Titan and the Moon. The mass of the satellite is 2.14 × 10 22 kg, which corresponds to 99.5% of the total mass of all currently known moons of Neptune. Triton revolves around Neptune in a slightly strange orbit. In addition to the fact that its orbit is an almost regular circle (it is ellipsoid for the rest of the satellites), Triton is also considered the only satellite in the solar system that moves in the direction of the reverse rotation of the planet (in this case, Neptune), while its orbit is strongly inclined to the plane the equator of the planet and the plane of the ecliptic by 157° and 130°, respectively. The ecliptic is understood as a large circle of the celestial sphere, along which the apparent annual movement of the Sun occurs. Triton is located at a distance of 354.8 thousand km from the center of Neptune and about 330 thousand km from its visible clouds. The satellite makes one revolution in 5 days 21 hours and 7 minutes at an average orbital speed of 15,800 km/h.

Surface of Triton It is covered with methane and nitrogen ice and therefore reflects sunlight quite well. The largest nitrogen lakes were seen by Voyager in the equatorial regions on the side facing Neptune. The satellite is not considered a favorite in terms of the number of impact craters on its surface. Only 179 impact craters were recorded by Voyager 2, and more than 800 impact craters were discovered on Uranus' moon Miranda for comparison. Such a calm situation on Triton may be due to the fact that its age is no more than 100 million years, when, like many other celestial bodies in the solar system, they were formed billions of years ago. It is also possible that most of the craters are hidden from the eyes of observers and the gaze of spacecraft in a dark, unlit hemisphere. After all, when Voyager 2 flew past Triton in the summer of 1989, it was able to explore only 40% of the moon's surface.

Unlike many moons in the solar system, Triton is surrounded by a thin a nitrogen-methane atmosphere. Although it is not entirely correct to name the atmosphere consisting of methane, since its content is not more than one tenth of a percent, while the remaining 99.9% is nitrogen. The pressure on the surface is 70,000 thousand times less than above sea level and the Earth's surface and is only 1.5 Pa. A weak air shell is formed due to volcanic emissions of nitrogen from the bowels of the satellite. Nitrogen, breaking through holes in the ice, carries dust particles to a height of up to 8 km, from where they, descending, can spread in plumes over distances of up to 150 km. Light floating particles remain in the air, replenishing the atmosphere, while larger ones settle on the surface in the form of nitrogen snow and hoarfrost. The minimum temperature recorded by the apparatus is -235 ° C, which in turn classifies Triton as the coldest celestial body in the solar system, colder even than on the distant planet Pluto and its dwarf neighbors.

An artist's view of Triton's surface. Against the background of the giant Neptune is shown

volcanic geyser, ejecting a fountain of nitrogenous gases to a height of about 8 km

particles and hard rocks. Some of them remain in the atmosphere, and some settle

to the surface in the form of white, as on Earth, snow

Nitrogen clouds that form 100 km above the surface of Triton

A high-quality image of the southern hemisphere of Triton taken by

Voyager 2 during its flyby in August 1989

Proteus

Satellite name: Proteus;

Diameter: 440 km;

Pov area: 607,900 km²;

Volume: 4.46 × 10 7 km³;

Weight: 5×10 19 kg;

Period of circulation: 1.12 days;

Distance from Neptune: 93,600 km;

Orbital speed: 7.63 km/s;

Orbital inclination: 0.04°;

Proteus or Neptune VIII - the largest inner satellite of the planet, as well as the second largest among all the moons of Neptune (after Triton). Proteus was discovered in images taken from the Voyager 2 spacecraft and named after a sea deity in ancient Greek mythology. The satellite itself is not a spherical body, i.e. its irregular shape looks like a large piece of heavenly stone. The dimensions of Proteus are 440x416x404 km, it is located at a distance of 93.6 thousand km from the visible disk of Neptune, and this puts the satellite in second place in terms of remoteness from the planet. The surface of Proteus is covered with impact craters up to several kilometers in diameter. Scientists do not know for sure the internal composition of the second moon of Neptune, however, one thing is certain: the satellite does not show any signs of volcanic and geological activity.

Nereid

And the seventh in distance from the planet. Triton was discovered in 1846 by William Lassell. This happened just a few weeks after the discovery of Neptune itself. In 1989, the Voyager 2 spacecraft visited the vicinity of Neptune. The data he relayed constitutes the majority of our knowledge of Triton to date.

Triton's strange orbit

Alone among the large satellites, Triton has a retrograde orbit. It only shares this feature with much smaller moons such as Ananke and Phoebe. It has been established that Triton could not have formed where it is now. Its backward movement suggests that it was born in the Kuiper Belt. And then was captured by Neptune (if so, it would be the most famous Kuiper belt object). The capture scenario could also explain the unusual orbit of Neptune's other moon, the Nereid. And also to explain the energy that once melted the surface of Triton.

Due to the retrograde orbit, tidal interactions between Neptune and Triton drain the latter's energy, causing it to break up. In the distant future, Triton will either collapse (possibly forming a ring) or crash into the planet.

Lateral rotation of Triton

Triton's axis of rotation is also unusual. It is tilted 157° from Neptune's axis (which in turn is tilted 30° from the plane of the planet's orbit). This makes Triton's orientation relatively the same as that of Uranus, with the polar and equatorial regions alternately facing the Sun.

Atmosphere of Triton

Triton has a very faint atmosphere, similar to Pluto's, with a surface pressure of about 0.01 millibars. It consists mainly of nitrogen with a small amount of methane. A thin haze extends for 5-10 kilometers. The temperature on the surface is as low as that of Pluto. This is a consequence of the high reflectivity of Triton's surface. It bounces most of the incoming sunlight back into space. In 1997, the eclipse of a star by Triton indicated that Triton had become slightly warmer since the Voyager flyby.

Composition of Triton

Triton is slightly denser than Saturn's icy moons. It is assumed that it probably consists of 25% water ice, and the rest of rocky material.

Features of Triton's surface

Voyager images show several craters. This indicates a relatively young surface of Triton. Nearly the entire southern hemisphere is covered in an ice cap of frozen nitrogen and methane. And the unique complex patterns found across much of the surface are likely the result of freeze/thaw cycles. The surface here is similar to the skin of a melon, which consists of approximately identical depressions. They range in size from 5 to 25 km across and are separated by rows of overlapping ridges. One hypothesis for their occurrence is that dimples are the result of internal explosions. Another explains them by melting and collapse of the ice surface.

Ice Volcanoes of Triton

The most interesting and completely unexpected features of Triton are its ice volcanoes. One of the images of Voyager shows a fantastic plume. It rises 8 km above the surface and extends 140 km downwind. Triton and Venus are the only bodies besides the Earth that are currently volcanically active (although they were referred to in the past).

It is also interesting to note that a wide variety of volcanic processes are taking place in the outer solar system. Eruptions on Earth and Venus erupt rocky material and come from internal heat. Eruptions on Io are sulfur compounds and are driven by tidal interaction with Jupiter. Whereas Triton eruptions are highly volatile compounds such as nitrogen or methane due to seasonal heating from the Sun.

There appear to be at least three types of icy volcanism on Triton.

The most distant planet in the solar system is Neptune. This is the first planet discovered using mathematical calculations.

The first evidence that the planet has its own ring system appeared in the mid-80s, and the study of Neptune by the Voyager 2 spacecraft only confirmed this conjecture. It was revealed that Neptune has a weak ring system, including 5 components, two of which are the brightest.

The rings are made up of small dust particles, they are more visible in diffused light. The rings have their own names. So the outer ring is Adams, it contains three distinctly visible arches, they also have very interesting names - Liberty, Equality and Fraternity. An explanation for the existence of arches has not yet been found, because in accordance with the laws on the momentum, the arches should have at least somehow changed in order to get a single ring. The satellite of Galatea, located inside the ring, is also not capable of keeping the arches in a stable state with its gravity.

Voyager 2 also discovered others - the Liverier ring and the barely visible Halle ring, as well as the elongated outer part of the Levier ring, called Lassel and the Arago ring.

The first satellite of the planet Neptune was discovered almost immediately with the discovery of the planet in 1846 by William Lassell and was named Triton. Only almost a hundred years later, the second satellite of Nereid was discovered, and then, thanks to Voyager 2, several more small satellites of Neptune were discovered in 1989, the rest were discovered in 2002-2003. In total for 2013, 13 satellites are known to orbit the planet. Here are the biggest ones:

Triton is Neptune's largest moon and has a thin atmosphere. It revolves around the planet in the opposite direction in a circle. Triton's surface is covered in nitrogen and methane ice, and has few impact craters. This indicates a relatively young age of the satellite. Triton revolves around Neptune in an orbit that is almost a regular circle. But as a result of the interaction of the planet and the satellite, a collision will occur in the distant future. Triton will either be destroyed, forming a new ring around Neptune, or will fall to the planet.

Proteus is the second largest moon of Neptune. Despite its large size, it was discovered later by Nereids. This is due to the very close location to the planet, which made it difficult to notice. Proteus has an irregular shape. Most likely, this is a fragment of one of the pre-existing satellites of Neptune, destroyed during the capture of the planet Triton. The surface of Proteus is covered with many craters, but no geological activity was detected on the satellite. There is a possibility that over time the satellite can change its shape, under the influence of gravity, and take the form of a sphere, to which it is very close today.

Nereid is the third largest moon of Neptune. It revolves around the planet in a very elongated orbit, and makes a full circle in 360 days. This suggests that Nereid is an asteroid. The satellite has no atmosphere, and the surface temperature is about -220 degrees. Until now, Nereid is the most unexplored satellite of the solar system.

Larissa is the fourth largest moon of Neptune. It was discovered by accident in 1981 as a result of observing Neptune from Earth. In 1989, its existence was confirmed. The surface contains a large number of craters, but no geological activity is observed. The origin of Larissa is similar to the origin of Proteus, which is also indicated by its irregular shape. The satellite's orbit is gradually decreasing, and after a while Larissa will be destroyed.

Neptune is one of the farthest and least explored planets in our solar system. If we consider the positions of celestial bodies from the Sun, Neptune will be the eighth - penultimate planet. For a long time, before the launch of Voyager 2, it was problematic to study this one not only because of its remoteness, but also because of the presence of a ring system that partially changes its shape. From the article it will become clear which planet has the satellites Triton and Nereid, what are their features and how they were discovered.

Astronomers divide the numerous satellites of Neptune into internal and external. Inner satellites are small celestial bodies held close to the planet by gravity and traveling in a circular orbital path. The outer ones are located at a distance from Neptune, have a fairly large mass and pass through unusual orbits.

Discovery of Neptune's moons

To date, 14 satellites of Neptune are known to orbit it. Most of them were discovered recently, when the path of the Voyager 2 spacecraft passed close to a distant planet, which made it possible to take detailed pictures. Prior to this, only two satellites were known - Nereid and the first Triton found.

The honor of discovering the largest satellite of Neptune, Triton, belongs to the English astronomer William Lassel. This happened in 1846, just 17 days after two famous German astronomers announced the discovery of the planet Neptune itself.

For a long time, Triton did not have its own name - it was designated on astronomical maps as a satellite of Neptune. And only after another satellite, Nereid, was discovered, did Triton get its official name.

The discovery of Nereid took place in 1949 - more than a hundred years after the planet itself and its first satellite were found in the sky. This discovery was made by the American astronomer Gerald Kuiper. It is surprising that he made this discovery using a ground-based telescope.

Mysterious Triton

The visit of the Voyager 2 spacecraft to Neptune confirmed the theoretical calculations of astronomers that Triton is the largest satellite of this distant planet. Its diameter is 2706 km, which is not much less than the diameter of the Moon. And the mass of Triton is only 3.5 times less than the satellite of our planet.

Its surface is completely covered with ice, consisting of frozen gases (methane and nitrogen), so the light of the Sun is well reflected from it and it can be seen through a telescope.

Triton rotates in an unusual orbit: it moves in the direction opposite to the movement of its planet, that is, it moves clockwise, and not against it. This movement is called retrograde. Another unusual thing is that Triton's orbit is almost a perfect circle and quite strongly inclined to the equator.

Based on the unusual characteristics of Triton, astronomers admit that this is not quite a satellite of the planet. Rather, it was an independent celestial body that was captured by the superior gravity of Neptune.

Distant satellite of Nereid

The diameter of this celestial body is approximately 340 km. It is considered the third largest satellite of Neptune, after Triton and Proteus. One of its revolutions around the planet lasts almost an Earth year - 360 days. Perhaps this is due to the fact that its orbit is highly elongated: it either approaches Neptune at a distance of 1.4 million kilometers, then it moves away by 9.66 million kilometers. Nereid, unlike Triton, has an irregular shape.

Such an unusual elongated orbit is not typical for the already studied satellites of planets in the solar system. This led astronomers to believe that Nereid used to be an asteroid, possibly from the Kuiper belt, that fell into Neptune's gravitational field and remained in its orbit.

Until now, scientists do not have detailed photos of Neptune's satellite Nereid. In 1989, the Voyager 2 spacecraft passed by Neptune, which took and sent back to Earth many pictures of the planet itself and its satellites. However, at that time, Nereid was at a very great distance and the device could not take detailed pictures of its surface. Therefore, this celestial body is still the least studied of the many satellites of Neptune.

Scientists have calculated that the mass of Triton is more than 90% of the total mass of all Neptune's moons. All the other numerous satellites of this planet, including Nereid, are significantly smaller.

The season on Triton lasts approximately forty Earth years.

Thanks to many years of observations, astronomers are sure that the structure of Triton resembles a planetary one: it has a stone core with a diameter of about 2000 kilometers, which is covered with a mixture of ice and rock fragments.

This satellite is considered one of the coldest space bodies in our galaxy - at an average temperature of -235 degrees Celsius, even nitrogen freezes on its surface. At the same time, operating geysers from nitrogen often appear on its surface, the height of which can reach ten meters. Thanks to this phenomenon, Triton has its own atmosphere, consisting of methane and nitrogen. As was recorded by Voyager 2, there are even clusters of clouds consisting of these gases above the surface of the satellite.

For a long time, astronomers considered the Nereid satellite to be the most distant, but, in the light of recent discoveries, this opinion has changed.

So far, most of the data is known to scientists thanks to the visit of the Voyager 2 spacecraft. However, there is a project to launch the next research vessel, planned for 2030.

The mysterious and distant Neptune has been known to astronomers for more than one hundred and seventy years. His discovery was a triumph of theoretical science. Despite the development of instrumental astronomy and unmanned astronautics, the planet keeps many secrets, and the unusual orbit of Neptune's satellite Triton is still the subject of discussion and hypotheses.

Janus? Neptune!

Initially, the eighth planet of the solar system wanted to be named after the ancient Roman god of the beginning and end - Janus. According to the discoverers, it was this cosmic body that personified the end of the "possessions" of our star, and the beginning of boundless outer space. And there were indeed several scientists who discovered the planet.

It all started with the fact that in 1834, a priest from England, insanely passionate about astronomy, T. D. Hussey, was very surprised, observing the recently discovered planet Uranus, that its true trajectory in the celestial sphere did not coincide with the calculated one. The Holy Father suggested that this deviation is caused by the influence of a massive space object located beyond the orbit of the gas giant.

Who is considered a pioneer?

The British scientist D. K. Adams and the Frenchman W. J. Le Verrier independently calculated the approximate position of an unknown body. According to the indicated coordinates, the German astronomer J. G. Halle (Berlin Observatory) and his assistant G. L. d'Arre discovered a mysterious "wandering" star on the very first night. It took scientists three days to finally make sure that the theoreticians' calculations and their observations were correct. Finally, on September 23, 1846, the discovery of the eighth planet of the solar system was announced to the world, which was assigned the name proposed by the Russian astronomer, director V.Ya. Struve - Neptune.

By the way, the final question of who should be considered the discoverer of the planet has not yet been resolved, but the whole story is a true triumph of celestial mechanics.

Within a month, the first satellite of Neptune was also discovered. For almost a century he did not have his own name. In 1880, the French astronomer K. Flammarion proposed to name the satellite Triton, but since it was the only one until 1949, the simple name, the satellite of Neptune, was more common in scientific circles. This celestial body, due to some of its features, deserves detailed consideration.

The primacy of the discovery of Triton (10/10/1846) belongs to the British astronomer W. Lassell. The dimensions of this largest satellite of Neptune are similar to those of the Moon, however, it is 3.5 times lighter in mass. This is due to the fact that Triton, presumably, a third consists of ice. The composition of the surface mantle includes frozen nitrogen, methane and water (from 15 to 30%). That is why the reflectivity of the satellite surface is very high and reaches 90% (the same indicator for the Moon is 12%). Despite the possible geological activity, this is perhaps the coldest object in the solar system with an average temperature of -235 ° C.

Not like everyone else

A distinctive feature of Triton is that it is the only large satellite known to science with retrograde rotation (the opposite of the planet's rotation around its own axis). In general, Triton's orbit is distinguished by unusual characteristics:

• almost perfect circle shape;
• a strong inclination to the planes of the ecliptic and the equator of the planet itself.

According to modern scientists, the largest satellite of Neptune was "captured" by a planet from the Kuiper Belt during one of the approaches. There is a hypothesis that the mutual tidal forces of the satellite and the planet noticeably heat up the latter, and the distance between them is steadily decreasing. Perhaps in the near future (by space standards, of course), the satellite, having entered the Roche limit, will be torn apart by the gravitational forces of the planet. In this case, a ring is formed around Neptune, which, with its size and splendor, will outshine the famous rings of Saturn.

The second satellite of the planet was discovered only in 1949 by the American D. Kuiper. Its name - Nereid - is a small celestial body (diameter about 340 km) was named after one of the sea nymphs in ancient Greek myths. The satellite has a very remarkable orbit, which has the largest eccentricity (0.7512) among the satellites not only of Neptune, but also of other planets. The minimum satellite approach distance is 1,100 thousand km, the maximum distance is about 9,600 thousand km. There are suggestions that Nereid was also once captured by the gas giant.

Larissa (another nymph) is the third and last satellite of the planet Neptune, discovered by earthly observers in the last century. It happened in 1981, thanks to some circumstances. Quite by accident, it was possible to fix the coverage of a star by this object. The final answer to the question of how many satellites Neptune has was given by the interplanetary space probe Voyager 2 (NASA), launched to explore the far reaches of the solar system. The device reached the outskirts of the planet in 1989 after a twelve-year journey.

Retinue of the underwater ruler

The names of the satellites of Neptune, one way or another, are associated with the god of the seas. To date, science is aware of 14 objects circling the planet. The Voyager 2 spacecraft also confirmed the existence of six rings, composed mainly of frozen methane. Five of them have their own names (as they move away from the surface of the planet): Halle, Le Verrier, Lassel, Argo and the Adams ring.

In general, the value of the information transmitted by Voyager for modern astronomy can hardly be overestimated. Six satellites were discovered, the presence of a weak nitrogen atmosphere on Triton, polar caps and traces of geological activity on its surface. During its work in the Neptune system, the automatic interplanetary station took more than 9,000 photographs.

Untitled S2004N1, Neso and others

From the list of Neptune's satellites, presented in the table according to their distance from the planet, you can get brief information about these cosmic bodies.

From the information presented, several noteworthy facts can be distinguished. The last satellite discovered in 2013 is the object S2004N1, which has not yet been assigned its own name.

The satellites of Neptune are usually divided into internal (from Naiad to Proteus) and external (from Triton to Neso). The former are characterized by a dark surface and irregular shape. Despina and Galatea, revolving around the rings, according to experts, are gradually destroyed and supply them with "building" material.

The outer satellites have very elongated orbits. Some parameters suggest that Galimede is a detached part of the Nereid. The distance of almost 49 million km makes it possible to consider Neso the most distant satellite in the solar system from its planet.