The secret of the ninth planet. Found a new dwarf planet on the outskirts of the solar system Planets of the solar system what's new

In general, I did not want to write anything on this topic. If you closely follow the news of astronomy, then the ninth planets are “discovered” almost every year. And these are always initial observations, and indirect signs that do not find confirmation. But today's news has spread across the top of the news and the headlines are rattling without an alternative "The ninth planet has been discovered." Not really. And now let's try to figure out what we found there.

First, a brief digression into the past.
Hypotheses that somewhere in the outskirts of the solar system a large planet or a brown dwarf flies have existed for a long time. They were looking for her at the beginning of the century, when they found. There are assumptions based on the fact that someone is constantly throwing comets from the distant Oort Cloud towards the Sun. But comets fly from all points of the celestial sphere, and not from any one plane, so the planet cannot be confirmed in this way. Although the names were already invented for her: both Nibiru, and Tyukhe and Planet X ...

In 2003, scientists discovered a rather large object, which today is considered one of the most distant objects in the solar system, except for long-period comets. The object was named Sedna. Its size is estimated at about a thousand kilometers, i.e. somewhere on Pluto's moon Charon.

Only redder. Sedna approaches the Sun no closer than 3 distances from the Sun to Neptune and moves away up to 30 distances. At that time, it had a unique orbit that had no analogues among known bodies.

In 2009, NASA launched the WISE space telescope with the goal of finding a large planet, if it exists at all, in the solar system.

And they didn't find anything. Those. the location of an unknown giant planet such as Jupiter or Saturn, or something more, is practically impossible for our star. Something smaller than Neptune might have been missed, but only if it was very far away. Highly !

In March 2014, another brother of Sedna was found - the smaller planetoid 2012 VP113. And just a few months later, scientists assumed that the features of the orbits of Sedna and VP113 are determined by as many as two large planets that orbit far beyond Neptune.

Just a month and a half ago, in December 2015, two more groups of scientists announced that discovered two objects while observing stars in the millimeter range with the ALMA telescope. While it is difficult to determine what they considered, and it is even impossible to calculate the distance to objects. They can either be nearby asteroids or distant planets.

These objects have nothing to do with Sedna, they are simply an illustration of the fact that astronomers constantly find something in the far vicinity of the Sun, but it is not yet determined what it is, it is too early to shout about sensational discoveries.

Now about today's "sensation". What was found there?
A pair of scientists: an astronomer and a mathematician from, decided to build a mathematical model that would explain the features of the movement of the "sednoids" discovered to date. Their model showed that it worked best if the factor of the gravitational interaction of these objects with an unknown planet with a mass of about 10 Earth masses was introduced into the equations.

Moreover, their calculations indicated that such a planet explains the behavior of another group of non-Neptunian objects, whose orbits are almost perpendicular to the orbits of those objects that were originally considered.

In more detail, the essence of today's discovery will tell Dmitry Wiebe, Doctor of Physical and Mathematical Sciences, Head of the Department of Physics and Evolution of Stars of the Institute of Astronomy of the Russian Academy of Sciences:

About Planet X

The periphery of the solar system is inhabited by objects sometimes collectively referred to as the Kuiper belt, but are actually several dynamically distinct groups - the classical Kuiper belt, the scattered disk, and resonant objects. The objects of the classical Kuiper belt revolve around the Sun in orbits with small inclinations and eccentricities, that is, in orbits of the "planetary" type. Scattered disk objects move in elongated orbits with perihelia in the region of Neptune's orbit, the orbits of resonant objects (Pluto among them) are in orbital resonance with Neptune.

The classical Kuiper belt ends rather abruptly at about fifty AU. Probably, it was there that the main boundary of the distribution of matter in the solar system passed. And although scattered disk objects and resonant objects at aphelion move away from the Sun by hundreds of astronomical units, at perihelion they are close to Neptune, indicating that both of them are connected by a common origin with the classical Kuiper belt, and were “attached” to their modern orbits gravitational influence of Neptune.

The picture began to get more complicated in 2003, when the trans-Neptunian object (TNO) Sedna was discovered with a perihelion distance of 76 AU. Such a significant distance from the Sun means that Sedna could not get into its orbit as a result of interaction with Neptune, and therefore there was an assumption that it is a representative of a more distant population of the solar system - the hypothetical Oort cloud.

For some time, Sedna was the only known object with such an orbit. The discovery of the second "sednoid" in 2014 was reported by Chadwick Trujillo and Scott Sheppard. The object 2012 VP113 revolves around the Sun in an orbit with a perihelion distance of 80.5 AU, that is, even more than that of Sedna. Trujillo and Sheppard noticed that both Sedna and 2012 VP113 have close values ​​of the perihelion argument - the angle between the directions to the perihelion and to the ascending node of the orbit (the point of its intersection with the ecliptic). Interestingly, similar values ​​of the perihelion argument (340° ± 55°) are typical for all objects with semi-major axes greater than 150 AU. and with perihelion distances greater than Neptune's perihelion distance. Trujillo and Sheppard suggested that such a grouping of objects near a particular value of the perihelion argument could be caused by the perturbing action of a distant massive (several Earth masses) planet.

A new paper by Batygin and Brown explores the possibility that the existence of such a planet could indeed explain the observed parameters of distant asteroids with similar values ​​of the perihelion argument. The authors analytically and numerically studied the motion of test particles on the periphery of the solar system over 4 billion years under the influence of a perturbing body with a mass of 10 Earth masses in an elongated orbit and showed that the presence of such a body actually leads to the observed configuration of TNO orbits with significant semi-major axes and perihelion distances . Moreover, the presence of an outer planet makes it possible to explain not only the existence of Sedna and other TNOs with similar values ​​of the perihelion argument. Unexpectedly for the authors in their simulations, the action of the perturbing body explained the existence of another population of TNOs, the origin of which has so far remained unclear, namely, the population of Kuiper belt objects in orbits with high inclinations. Finally, the work of Batygin and Brown predicts the existence of objects with large perihelion distances and other values ​​of the perihelion argument, which provides an additional observational verification of their prediction.

But, of course, the main test should be the discovery of the "troublemaker" itself - the very planet whose attraction, according to the authors, determines the distribution of bodies with perihelions outside the classical Kuiper belt. The task of finding it is very difficult. Most of the time, "Planet X" should spend near aphelion, which can be located at a distance of over 1000 AU. from the sun. Calculations indicate the possible location of the planet very approximately - its aphelion is located approximately in the direction opposite to the direction on the aphelions of the studied TNOs, but the orbital inclination cannot be determined from the data on the available TNOs with large semi-major axes of the orbits. So the review of a very large area of ​​​​the sky, where an unknown planet may be located, will last for many years. The search may become easier if other TNOs moving under the influence of Planet X are discovered, which will narrow the range of possible values ​​​​of its orbital parameters.

Summing up, it should be recognized that the journalists once again seized on the sensation without understanding, and smashed around the world what was not there. Partly to blame for this and scientists who rushed to the conclusions and their publication. But they can be understood - in this way they at least push through the beginning of the search for the planet with large telescopes, to which they do not have access now.

Exactly two years ago, California Institute of Technology scientists Konstantin Batygin and Michael Brown published, resurrecting hopes that another planet could be found in the solar system, located much farther than Pluto. More about the history of the search for the ninth planet and the significance of the calculations of Batygin and Brown at the request N+1 says blogger and promoter of astronautics Vitaly "Green Cat" Egorov.

In the astronomical environment, for two years they have been discussing a sensation that does not yet exist. A number of indirect signs indicate that somewhere in the solar system, much further than Pluto, there is another planet. So far, it has not been found, but the approximate location has been calculated. If there is no error in the calculations, then this will be the most important astronomical discovery of the century.

The first planet discovered "on the tip of a pen" was Neptune - back in the 1830s, astronomers drew attention to unforeseen deviations in the orbit of Uranus and suggested that there was another planet behind it, which caused a gravitational perturbation. The hypothesis was confirmed in 1846, when Neptune could be observed in a mathematically predicted region of the sky. It turned out that he had been seen before, but could not be distinguished from distant stars. The average distance to Neptune is 4.5 billion kilometers, or about 30 astronomical units (one astronomical unit is equal to the distance from the Sun to the Earth - about 150 million kilometers).

The optimism after the discovery of Neptune inspired many scientists and amateur astronomers to search for other, more distant planets. Further observations of Neptune and Uranus showed a discrepancy between the actual movement of the planets and the mathematically predicted, and this gave confidence that the sensation of 1846 could be repeated. It seemed that in 1930 the search was crowned with success when Clyde Tombaugh discovered Pluto at a distance of about 40 astronomical units.

Clyde Tombaugh

For a long time, Pluto was the only known object in the solar system located farther from the Sun than Neptune. And as the quality of astronomical technology grew, ideas about the size of Pluto constantly changed downward. By the middle of the century, it was believed that it had a size comparable to the Earth, and a very dark surface. In 1978, it was possible to clarify the mass of Pluto thanks to the discovery of its satellite Charon. It turned out that it is much smaller not only than Mercury, but even the Earth's Moon.

By the end of the 20th century, thanks to digital photography and computer data processing, discoveries of other trans-Neptunian objects smaller than Pluto began. At first, out of habit, they were called planets. There were ten of them in the solar system, then eleven, then twelve. But by the early 2000s, astronomers sounded the alarm. It became clear that the solar system does not end beyond Neptune, and it is not good to give the status of Earth and Jupiter to each ice block. In 2006, a separate name was coined for pluto-like bodies - a dwarf planet. There are eight planets again, just like a century ago.

Meanwhile, the search for real planets outside the orbits of Neptune and Pluto did not stop. There were even hypotheses about the presence of a red or brown dwarf there, that is, a small star-like body with a mass of several tens of Jupiters, which makes up a double star system with the Sun. This hypothesis was prompted by ... dinosaurs and other extinct animals. A group of scientists drew attention to the fact that mass extinctions on Earth occur approximately every 26 million years, and suggested that this is the period of the return of a massive body to the vicinity of the inner solar system, which leads to an increase in the number of comets rushing towards the Sun and hitting the Earth. In many media, these hypotheses came in the form of anti-scientific predictions about an impending attack by aliens from the planet or star Nibiru.

On the X axis - millions of years before the present day, on the Y axis - bursts of extinction of biological species on Earth

NASA has twice attempted to find a possible planet or brown dwarf. In 1983, the IRAS space telescope carried out a complete mapping of the celestial sphere in the infrared range. The telescope has made observations of tens of thousands of sources of thermal radiation, discovered several asteroids and comets in the solar system, and caused a sensation in the press when scientists mistakenly mistook a distant galaxy for a Jupiter-like planet. In 2009, a similar, but more sensitive and long-lived WISE telescope flew, which managed to find several brown dwarfs, but at a distance of several light years, that is, not related to the solar system. He also showed that in our system there are no planets the size of Saturn or Jupiter beyond Neptune either.

No one has been able to see a new planet or a nearby star so far. Either it is not there at all, or it is too cold and emits or reflects too little light to be detected by a random search. Scientists still have to rely on indirect signs: the features of the movement of other, already discovered cosmic bodies.

At first, encouraging data was obtained in the anomalies of the orbits of Uranus and Neptune, but in 1989 it was found that the reason for the anomalies was an erroneous determination of the mass of Neptune: it turned out to be five percent lighter than previously thought. After correcting the data, the simulation began to coincide with the observations, and the hypothesis of the ninth planet was dropped.

Some researchers have thought about the reasons for the appearance of long-period comets in the inner solar system and about the source of short-period comets. Long-period comets can appear near the Sun once every hundreds or millions of years. Short-period orbits around the Sun in 200 years or less, that is, they are much closer.

Comets have a very short lifetime by cosmic standards. Their main material is ice of various origins: from water, methane, cyanide, etc. The sun's rays evaporate the ice, and the comet turns into an imperceptible stream of dust. However, short-period comets continue to circle the Sun today, billions of years after the formation of the solar system. This means that their number is replenished from some external source.

The Oort Cloud is considered such a source - a hypothetical region with a radius of up to 1 light year, or 60 thousand astronomical units, around the Sun. It is believed that there are millions of pieces of ice flying in circular orbits. But periodically something changes their orbit and launches them towards the Sun. What this force is is still unknown: it may be a gravitational disturbance from neighboring stars, the results of collisions in a cloud, or the influence of a large body in it. For example, it could be a planet a little larger than Jupiter - it was even given the name Tyukhe. The authors of the Tyche hypothesis assumed that the WISE telescope would be able to find it, but the discovery did not take place.

Oort cloud (above: the orange line shows the conditional orbit of objects from the Kuiper belt, the yellow line shows the orbit of Pluto

If the Oort Cloud is only a hypothetical family of small Solar System bodies that astronomers cannot observe directly, then another family, the Kuiper Belt, is much better understood. Pluto is the first Kuiper Belt body to be discovered. Three more dwarf planets the size of Pluto or smaller and more than a thousand small bodies have now been discovered there.

The Kuiper belt family is characterized by circular orbits, a slight inclination to the plane of rotation of the known planets of the solar system - the plane of the ecliptic - and circulation within 30 and 55 astronomical units. On the inner side, the Kuiper belt breaks off in the orbit of Neptune, in addition, this planet exerts a gravitational perturbation on the belt. The reason for the sharp outer boundary of the belt is unknown. This suggests the presence of another full-fledged planet somewhere at a distance of 50 astronomical units.

Behind the Kuiper belt, although partially intersecting with it, lies the region of the scattered disk. On the contrary, the small bodies of this disk are characterized by highly elongated elliptical orbits and a significant inclination to the ecliptic plane. New hopes for the discovery of the ninth planet and heated discussions among astronomers gave rise to the bodies of the scattered disk.

Some objects in the scattered disk are so far from Neptune that it has no gravitational influence on them. A separate term "isolated trans-Neptunian object" was coined for them. One such known object called Sedna approaches the Sun by 76 astronomical units and moves away by 1000 astronomical units, so it is simultaneously considered the first found object of the Oort Cloud. Some known bodies of the scattered disk have less extreme orbits, and some, on the contrary, have an even more elongated orbit and a strong inclination of the orbital plane.

According to the calculations of the authors of the fresh hypothesis, "their" planet can have an elongated orbit, approaching the Sun by 200 and moving away by 1200 astronomical units. Its exact location in the earth's sky has not yet been calculated, but the approximate search area is gradually shrinking. The search is being conducted using the Subaru Optical Telescope in Hawaii and the Victor Blanco Telescope in Chile. In order to further confirm the existence of the planet and clarify its possible location, it is required to find more bodies of the scattered disk. Now these searches are ongoing, the work has a high priority, and new finds are emerging. However, the expected planet is still elusive.

If astronomers knew where to look, they might be able to see the planet and estimate its size. But "long-range" telescopes have too narrow a field of view to carry out a free search over large areas of the sky. For example, the famous Hubble space telescope has examined less than 10 percent of the entire celestial sphere in its 25 years of operation. But the search continues, and if the ninth planet of the solar system is still found, it will become a real sensation in astronomy.

Vitaly Egorov

MOSCOW, October 2 - RIA Novosti. Astronomers have discovered another dwarf planet in the solar system, trying to find the mysterious "planet X". Its discovery raises the chances that this gas giant exists, according to an article published in the Astronomical Journal.

"These distant worlds, in fact, can be called a kind of cosmic road signs that show us the way to" planet X ". The more we find them, the better we will understand how the outskirts of the solar system are arranged and how this planet, if it exists, “conducts” their lives,” said Scott Sheppard of the Carnegie Institution of Science in Washington (USA).

Mysteries of "planet x"

Recently, scientists have discovered several large dwarf planets and objects on the outskirts of the solar system, proving that "life" in it does not end beyond the orbits of Neptune and Pluto and that large celestial bodies continue to be encountered at greater distances.

So, in 2014, Sheppard and his colleague Chad Trujillo (Chad Trujillo) announced the discovery of Biden - the plutoid 2012 VP113, moving away from the Sun by 12 billion kilometers, and in 2015 they discovered the dwarf planet V774104, moving away from the star even further.

Scientists say they have spent the last few years searching for the mysterious "Planet X" - the fifth gas giant in the solar system, hints of whose existence were found by Konstantin Batygin and Michael Brown in the data collected by Trujillo and Sheppard while observing Biden.

Two years ago, Trujillo and Sheppard found three large dwarf planets orbiting in unusual - extremely elongated - trajectories, trying to find "planet X" in the course of a systematic census of distant worlds in the solar system. They failed to solve this problem, but the discovery of three new planets strengthened their suspicions that Batygin and Brown's gas giant really existed.

Analyzing the movement of these planets, as well as Biden and a number of other celestial bodies beyond the orbit of Pluto, scientists drew attention to the fact that their orbits are very similar to each other. This prompted the idea that other planets, if they exist between Pluto and the Oort cloud, should be located approximately in the same place.

Guided by this idea, scientists continued their observations, focusing the attention and lenses of telescopes on those parts of the sky through which the "permissible" orbits of such "outlying" worlds pass. Such tactics quickly paid off - Trujillo and Sheppard managed to find another dwarf planet just a year after the discovery of the previous "troika" of celestial bodies.

Visiting the Goblin

This world, officially named 2015 TG387 and unofficially nicknamed Goblin, is similar in properties to Biden and his other neighbors. It has a diameter of about 300 kilometers, which classifies it as a medium-sized dwarf planet, and moves in an elongated orbit that goes far into the Oort cloud.

Its closest point to the Sun is at a distance of about 65 astronomical units, the average distance between the luminary and the Earth, while the farthest point is 1200 units away from it. This makes Goblin the third most distant dwarf planet - only Biden and Sedna approach the Sun at greater distances than 2015 TG387.

© Roberto Molar Candanosa, Scott Sheppard // Carnegie Institution for ScienceOrbits of Goblin, Biden and Sedna

© Roberto Molar Candanosa, Scott Sheppard // Carnegie Institution for Science

Adding this planet to the computer models of the solar system, indicating the existence of "planet X", increases their stability. This, Sheppard notes, indicates that this world really exists - if "planet X" was a fiction, then the virtual solar system would become unstable when the Goblin was added, the existence of which was not known to scientists when developing this model.

Interestingly, the calculations indicate that the planet of Batygin and Brown can move in a retrograde orbit, rotating in the opposite direction with respect to the Sun and most of the worlds of our planetary family. According to scientists, the discovery of other dwarf planets, similar to the Goblin, will strengthen the position of this hypothesis.

“It should be understood that our calculations and observations do not necessarily indicate that “planet X” exists. On the other hand, they indicate that there really is some kind of large object on the outskirts of the solar system,” concludes Trujillo.

Planets of the solar system

According to the official position of the International Astronomical Union (IAU), an organization that assigns names to astronomical objects, there are only 8 planets.

Pluto was removed from the category of planets in 2006. because in the Kuiper belt are objects that are larger / or equal in size to Pluto. Therefore, even if it is taken as a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size with Pluto.

As defined by MAC, there are 8 known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

All planets are divided into two categories depending on their physical characteristics: terrestrial and gas giants.

Schematic representation of the location of the planets

terrestrial planets

Mercury

The smallest planet in the solar system has a radius of only 2440 km. The period of revolution around the Sun, for ease of understanding, equated to the earth's year, is 88 days, while Mercury has time to complete a revolution around its own axis only one and a half times. Thus, its day lasts approximately 59 Earth days. For a long time it was believed that this planet is always turned to the Sun by the same side, since the periods of its visibility from the Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the possibility of using radar research and conducting continuous observations using space stations. The orbit of Mercury is one of the most unstable; not only the speed of movement and its distance from the Sun change, but also the position itself. Anyone interested can observe this effect.

Mercury in color, as seen by the MESSENGER spacecraft

Mercury's proximity to the Sun has caused it to experience the largest temperature fluctuations of any of the planets in our system. The average daytime temperature is about 350 degrees Celsius, and the nighttime temperature is -170 °C. Sodium, oxygen, helium, potassium, hydrogen and argon have been identified in the atmosphere. There is a theory that it was previously a satellite of Venus, but so far this remains unproven. It has no satellites of its own.

Venus

The second planet from the Sun, the atmosphere of which is almost entirely composed of carbon dioxide. It is often called the Morning Star and the Evening Star, because it is the first of the stars to become visible after sunset, just as before dawn it continues to be visible even when all other stars have disappeared from view. The percentage of carbon dioxide in the atmosphere is 96%, there is relatively little nitrogen in it - almost 4%, and water vapor and oxygen are present in very small amounts.

Venus in the UV spectrum

Such an atmosphere creates a greenhouse effect, the temperature on the surface because of this is even higher than that of Mercury and reaches 475 ° C. Considered the slowest, the Venusian day lasts 243 Earth days, which is almost equal to a year on Venus - 225 Earth days. Many call it the sister of the Earth because of the mass and radius, the values ​​​​of which are very close to the earth's indicators. The radius of Venus is 6052 km (0.85% of the earth). There are no satellites, like Mercury.

The third planet from the Sun and the only one in our system where there is liquid water on the surface, without which life on the planet could not develop. At least life as we know it. The radius of the Earth is 6371 km and, unlike the rest of the celestial bodies in our system, more than 70% of its surface is covered with water. The rest of the space is occupied by the continents. Another feature of the Earth is the tectonic plates hidden under the planet's mantle. At the same time, they are able to move, albeit at a very low speed, which over time causes a change in the landscape. The speed of the planet moving along it is 29-30 km / s.

Our planet from space

One rotation around its axis takes almost 24 hours, and a complete orbit lasts 365 days, which is much longer in comparison with the nearest neighboring planets. The Earth day and year are also taken as a standard, but this is done only for the convenience of perceiving time intervals on other planets. The Earth has one natural satellite, the Moon.

Mars

The fourth planet from the Sun, known for its rarefied atmosphere. Since 1960, Mars has been actively explored by scientists from several countries, including the USSR and the USA. Not all research programs have been successful, but water found in some areas suggests that primitive life exists on Mars, or existed in the past.

The brightness of this planet allows you to see it from Earth without any instruments. Moreover, once every 15-17 years, during the Opposition, it becomes the brightest object in the sky, eclipsing even Jupiter and Venus.

The radius is almost half that of the earth and is 3390 km, but the year is much longer - 687 days. He has 2 satellites - Phobos and Deimos .

Visual model of the solar system

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• Sun

  The sun is a star, which is a hot ball of hot gases at the center of our solar system. Its influence extends far beyond the orbits of Neptune and Pluto. Without the Sun and its intense energy and heat, there would be no life on Earth. There are billions of stars, like our Sun, scattered throughout the Milky Way galaxy.

• Mercury

  Sun-scorched Mercury is only slightly larger than Earth's moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from the fall of meteorites, therefore, like the Moon, it is covered with craters. The day side of Mercury is very hot on the Sun, and on the night side the temperature drops hundreds of degrees below zero. In the craters of Mercury, which are located at the poles, there is ice. Mercury makes one revolution around the Sun in 88 days.

• Venus

  Venus is a world of monstrous heat (even more than on Mercury) and volcanic activity. Similar in structure and size to Earth, Venus is covered in a thick and toxic atmosphere that creates a strong greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the mighty atmosphere revealed volcanoes and deformed mountains. Venus rotates in the opposite direction from the rotation of most planets.

• Earth is an ocean planet. Our home, with its abundance of water and life, makes it unique in our solar system. Other planets, including several moons, also have ice deposits, atmospheres, seasons, and even weather, but only on Earth did all these components come together in such a way that life became possible.

• Mars

  Although details of the surface of Mars are difficult to see from Earth, telescope observations show that Mars has seasons and white spots at the poles. For decades, people have assumed that the bright and dark areas on Mars are patches of vegetation and that Mars might be a suitable place for life, and that water exists in the polar caps. When the Mariner 4 spacecraft flew by Mars in 1965, many of the scientists were shocked to see pictures of the bleak, cratered planet. Mars turned out to be a dead planet. More recent missions, however, have revealed that Mars holds many mysteries that have yet to be solved.

• Jupiter

  Jupiter is the most massive planet in our solar system, has four large moons and many small moons. Jupiter forms a kind of miniature solar system. To turn into a full-fledged star, Jupiter had to become 80 times more massive.

• Saturn

  Saturn is the most distant of the five planets that were known before the invention of the telescope. Like Jupiter, Saturn is made up mostly of hydrogen and helium. Its volume is 755 times that of the Earth. Winds in its atmosphere reach speeds of 500 meters per second. These fast winds, combined with heat rising from the planet's interior, cause the yellow and golden streaks we see in the atmosphere.

• Uranus

  The first planet found with a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet is so far from the Sun that one revolution around the Sun takes 84 years.

• Neptune

  Nearly 4.5 billion kilometers from the Sun, distant Neptune rotates. It takes 165 years to complete one revolution around the Sun. It is invisible to the naked eye due to its vast distance from Earth. Interestingly, its unusual elliptical orbit intersects with the orbit of the dwarf planet Pluto, which is why Pluto is inside Neptune's orbit for about 20 out of 248 years during which it makes one revolution around the Sun.

• Pluto

  Tiny, cold and incredibly distant, Pluto was discovered in 1930 and has long been considered the ninth planet. But after the discovery of Pluto-like worlds even further away, Pluto was reclassified as a dwarf planet in 2006.

The planets are giants

There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are in the outer solar system. They differ in their massiveness and gas composition.

Planets of the solar system, not to scale

Jupiter

The fifth planet from the Sun and the largest planet in our system. Its radius is 69912 km, it is 19 times larger than the Earth and only 10 times smaller than the Sun. A year on Jupiter is not the longest in the solar system, lasting 4333 Earth days (incomplete 12 years). His own day has a duration of about 10 Earth hours. The exact composition of the planet's surface has not yet been determined, but it is known that krypton, argon and xenon are present on Jupiter in much larger quantities than on the Sun.

There is an opinion that one of the four gas giants is actually a failed star. This theory is also supported by the largest number of satellites, of which Jupiter has many - as many as 67. To imagine their behavior in the orbit of the planet, a fairly accurate and clear model of the solar system is needed. The largest of them are Callisto, Ganymede, Io and Europa. At the same time, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% larger than the size of Mercury, the smallest planet in our system. Io has the distinction of being one of only three moons with an atmosphere.

Saturn

The second largest planet and the sixth largest in the solar system. In comparison with other planets, the composition of chemical elements is most similar to the Sun. The surface radius is 57,350 km, the year is 10,759 days (almost 30 Earth years). A day here lasts a little longer than on Jupiter - 10.5 Earth hours. In terms of the number of satellites, it is not far behind its neighbor - 62 versus 67. The largest satellite of Saturn is Titan, just like Io, which is distinguished by the presence of an atmosphere. Slightly smaller than it, but no less famous for this - Enceladus, Rhea, Dione, Tethys, Iapetus and Mimas. It is these satellites that are the objects for the most frequent observation, and therefore we can say that they are the most studied in comparison with the rest.

For a long time, the rings on Saturn were considered a unique phenomenon, inherent only to him. Only recently it was found that all gas giants have rings, but the rest are not so clearly visible. Their origin has not yet been established, although there are several hypotheses about how they appeared. In addition, it was recently discovered that Rhea, one of the satellites of the sixth planet, also has some kind of rings.