Solar system age. Solar system planets in order

solar system is one of 200 billion star systems located in the Milky Way galaxy. It is located approximately in the middle between the center of the galaxy and its edge.
The solar system is a certain accumulation of celestial bodies that are connected by gravitational forces with a star (the Sun). It includes: the central body - the Sun, 8 large planets with their satellites, several thousand small planets or asteroids, several hundred observed comets and an infinite number of meteoric bodies.

Large planets are divided into 2 main groups:
- terrestrial planets (Mercury, Venus, Earth and Mars);
- planets of the Jupiter group or giant planets (Jupiter, Saturn, Uranus and Neptune).
Pluto has no place in this classification. In 2006, it was found that Pluto, due to its small size and great distance from the Sun, has a low gravitational field and its orbit is not similar to the orbits of planets adjacent to it, closer to the Sun. In addition, the elongated ellipsoidal orbit of Pluto (for the rest of the planets it is almost circular) intersects with the orbit of the eighth planet solar system- Neptune. That is why, since recent times, it was decided to deprive Pluto of the status of a "planet".

terrestrial planets are relatively small and have a high density. Their main constituents are silicates (silicon compounds) and iron. At giant planets virtually no hard surface. These are huge gas planets, formed mainly from hydrogen and helium, the atmosphere of which, gradually condensing, smoothly passes into a liquid mantle.
Of course, the main elements The solar system is the sun. Without it, all the planets, including ours, would have scattered over great distances, and perhaps even beyond the galaxy. It is the Sun, due to its huge mass (99.87% of the mass of the entire solar system), that creates an incredibly powerful gravitational effect on all planets, their satellites, comets and asteroids, forcing each of them to rotate in its own orbit.

V solar system, in addition to planets, there are two areas filled with small bodies (dwarf planets, asteroids, comets, meteorites). The first area is Asteroid Belt, which is between Mars and Jupiter. In composition, it is similar to the terrestrial planets, as it consists of silicates and metals. Beyond Neptune is a second region called Kuiper Belt. It has many objects (mostly dwarf planets) consisting of frozen water, ammonia and methane, the largest of which is Pluto.

The Koipner belt begins just after the orbit of Neptune.

Its outer ring ends at a distance

8.25 billion km from the Sun. This is a huge ring around the whole

The solar system is an infinite

the amount of volatile substances from ice floes of methane, ammonia and water.

The Asteroid Belt is located between the orbits of Mars and Jupiter.

The outer boundary is located 345 million km from the Sun.

Contains tens of thousands, possibly millions of objects more than one

kilometers in diameter. The largest of them are dwarf planets

(diameter from 300 to 900 km).

All planets and most other objects revolve around the Sun in the same direction as the Sun's rotation (counterclockwise when viewed from the side). north pole sun). Mercury has the highest angular velocity - it manages to make a complete revolution around the Sun in just 88 Earth days. And for the most distant planet - Neptune - the period of revolution is 165 Earth years. Most of The planets revolve around their axis in the same direction as they revolve around the sun. The exceptions are Venus and Uranus, and Uranus rotates almost "lying on its side" (axis tilt is about 90 °).

It was previously assumed that boundary of the solar system ends just after Pluto's orbit. However, in 1992 new celestial bodies, which undoubtedly belong to our system, as they are directly under the gravitational influence of the Sun.

Each celestial object is characterized by such concepts as a year and a day. Year- this is the time for which the body turns around the Sun at an angle of 360 degrees, i.e. makes a complete circle. A day is the period of rotation of the body around its own axis. The closest planet from the Sun, Mercury, revolves around the Sun in 88 Earth days, and around its axis - in 59 days. This means that even less than two days pass on the planet in one year (for example, on Earth, one year includes 365 days, i.e. that is how many times the Earth turns around its axis in one revolution around the Sun). While on the most distant, from the Sun, dwarf planet Pluto, a day is 153.12 hours (6.38 Earth days). And the period of revolution around the Sun is 247.7 Earth years. That is, only our great-great-great-great-grandchildren will catch the moment when Pluto finally goes all the way in its orbit.

galactic year. In addition to circular motion in orbit, the solar system performs vertical oscillations relative to the galactic plane, crossing it every 30-35 million years and ending up either in the northern or southern galactic hemisphere.
Disturbing factor for the planets solar system is their gravitational influence on each other. It slightly changes the orbit compared to that in which each planet would move under the action of the Sun alone. The question is whether these perturbations can accumulate up to the fall of the planet on the Sun or its removal beyond solar system, or they are periodic and the orbital parameters will only fluctuate around some average values. Results of theoretical and research work performed by astronomers in more than 200 recent years, speak in favor of the second assumption. This is also evidenced by the data of geology, paleontology and other Earth sciences: for 4.5 billion years, the distance of our planet from the Sun has practically not changed. And in the future, neither falling on the Sun, nor leaving solar system, as well as the Earth, and other planets are not threatened.

On March 13, 1781, English astronomer William Herschel discovered the seventh planet in the solar system - Uranus. And on March 13, 1930, American astronomer Clyde Tombaugh discovered the ninth planet in the solar system - Pluto. By the beginning of the 21st century, it was believed that the solar system included nine planets. However, in 2006, the International Astronomical Union decided to strip Pluto of this status.

There are already 60 known natural satellites of Saturn, most of which have been discovered using spacecraft. Most satellites are made up of rocks and ice. The largest satellite, Titan, discovered in 1655 by Christian Huygens, is larger than the planet Mercury. The diameter of Titan is about 5200 km. Titan orbits Saturn every 16 days. Titan is the only satellite to have a very dense atmosphere, 1.5 times the size of Earth's, and consisting mostly of 90% nitrogen, with a moderate amount of methane.

The International Astronomical Union officially recognized Pluto as a planet in May 1930. At that moment, it was assumed that its mass was comparable to the mass of the Earth, but later it was found that the mass of Pluto is almost 500 times less than the Earth's, even less than the mass of the Moon. The mass of Pluto is 1.2 times 1022 kg (0.22 Earth masses). The average distance of Pluto from the Sun is 39.44 AU. (5.9 by 10 to the 12th degree km), the radius is about 1.65 thousand km. The period of revolution around the Sun is 248.6 years, the period of rotation around its axis is 6.4 days. The composition of Pluto supposedly includes rock and ice; the planet has a thin atmosphere composed of nitrogen, methane and carbon monoxide. Pluto has three moons: Charon, Hydra and Nyx.

At the end of XX and early XXI centuries, many objects have been discovered in the outer part of the solar system. It has become clear that Pluto is only one of the largest Kuiper belt objects known to date. Moreover, at least one of the objects of the belt - Eris - is a larger body than Pluto and 27% heavier than it. In this regard, the idea arose to no longer consider Pluto as a planet. On August 24, 2006, at the XXVI General Assembly of the International Astronomical Union (IAU), it was decided to henceforth call Pluto not a "planet", but a "dwarf planet".

At the conference, a new definition of the planet was developed, according to which planets are considered to be bodies revolving around a star (and not being a star themselves), having a hydrostatically balanced shape and "clearing" the area in the region of their orbit from other, smaller, objects. Dwarf planets will be considered objects that revolve around a star, have a hydrostatically equilibrium shape, but have not "cleared" the nearby space and are not satellites. Planets and dwarf planets are two different classes of solar system objects. All other objects revolving around the Sun and not being satellites will be called small bodies of the solar system.

Thus, since 2006, there have been eight planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Five dwarf planets are officially recognized by the International Astronomical Union: Ceres, Pluto, Haumea, Makemake, and Eris.

On June 11, 2008, the IAU announced the introduction of the concept of "plutoid". It was decided to call plutoids celestial bodies that revolve around the Sun in an orbit whose radius is greater than the radius of Neptune's orbit, whose mass is sufficient for gravitational forces to give them an almost spherical shape, and which do not clear the space around their orbit (that is, many small objects revolve around them ).

Since it is still difficult to determine the shape and thus the relation to the class of dwarf planets for such distant objects as plutoids, scientists recommended temporarily assigning to plutoids all objects whose absolute asteroid magnitude (brilliance from a distance of one astronomical unit) is brighter than +1. If it later turns out that the object assigned to the plutoids is not a dwarf planet, it will be deprived of this status, although the assigned name will be left. The dwarf planets Pluto and Eris were classified as plutoids. In July 2008, Makemake was included in this category. On September 17, 2008, Haumea was added to the list.

The material was prepared on the basis of information from open sources

The new words didn't fit in my head. It also happened that a textbook of natural history set before us the goal - to remember the location of the planets of the solar system, and we were already choosing means to justify it. Among the many options for solving this problem, there are several interesting and efficient ones.

Mnemonic in its purest form

The way out for modern students was invented by the ancient Greeks. No wonder the term "mnemonics" comes from a consonant Greek word, meaning in literal translation "the art of remembering." This art gave rise to a whole system of actions aimed at memorizing a large amount of information - "mnemonics".

They are very convenient to use if you just need to memorize a whole list of any names, a list of important addresses or phone numbers, or remember the sequence of objects. In the case of the planets of our system, such a technique is simply irreplaceable.

We play associations or "Ivan gave birth to a girl ..."

Each of us remembers and knows this rhyme since elementary school. This is the mnemonic counter. We are talking about that couplet, thanks to which it becomes easier for a child to remember the cases of the Russian language - “Ivan gave birth to a girl - He ordered to drag the diaper” (respectively - Nominative, Genitive, Dative, Accusative, Instrumental and Prepositional).

Is it possible to do the same with the planets of the solar system? - Undoubtedly. A mnemonic for this astronomical educational program has already been invented quite a large number of. The main thing you need to know: they are all based on associative thinking. It is easier for someone to imagine an object similar in form to a memorized one, for someone it is enough to present a chain of names in the form of a kind of “cipher”. Here are just a few tips on how best to memorize their location, taking into account the distance from the central star.

Funny pictures

The sequence of removal of the planets of our star system from the Sun can be remembered through visual images. First, associate with each planet an image of an object or even a person. Then imagine these pictures one by one, in the sequence in which the planets are located inside the solar system.

Mercury. If you have never seen images of this ancient Greek god, try to remember the late lead singer of the Queen group - Freddie Mercury, whose last name is consonant with the name of the planet. It is unlikely, of course, that children can know who this uncle is. Then we propose to come up with simple phrases, where the first word would begin with the syllable MEP, and the second with KUR. And they must necessarily describe specific objects, which will then become a “picture” for Mercury (this method can be used as the most extreme option with each of the planets).
Venus. Many have seen the statue of Venus de Milo. If you show it to your children, they can easily remember this "armless aunt." Plus, enlighten the next generation. You can ask them to remember some friend, classmate or relative with that name - all of a sudden there are such in the circle of friends.
Land. Everything is simple here. Everyone must imagine himself, an inhabitant of the Earth, whose “picture” stands between two planets located in space before and after ours.
Mars. In this case, advertising can become not only an "engine of trade", but also scientific knowledge. We think you understand that you need to introduce a popular imported chocolate in the place of the planet.
Jupiter. Try to imagine some landmark of St. Petersburg, for example, the Bronze Horseman. Yes, even if the planet starts in Yu, but " northern capital» the locals call Peter. Such an association may not be useful for children, so invent a phrase with them.
Saturn. Such a “handsome man” does not need any visual image, because everyone knows him as a planet with rings. If there are still difficulties, imagine a sports stadium with a treadmill. Moreover, such an association has already been used by the creators of one animated film on a space theme.
Uranus. The most effective in this case will be the “picture”, in which someone is very happy about some achievement and, as it were, shouts “Hurrah!”. Agree - every child is capable of adding one letter to this exclamation.
Neptune. Show the children the cartoon "The Little Mermaid" - let them remember Ariel's dad - the King with a mighty beard, impressive muscles and a huge trident. And it does not matter that according to the plot, His Majesty is called Triton. Neptune, after all, also had this tool in his arsenal.

And now - once again mentally imagine everything (or all) that reminds you of the planets of the solar system. Flip through these images, like pages in a photo album, from the first "picture", the closest to the Sun, to the last, whose distance from the star is the greatest.

“Look, what kind of POINTS have turned out ...”

Now - to mnemonics, which are based on the "initials" of the planets. Remembering the order of the planets in the solar system is really the easiest thing to do by the first letters. This kind of "art" is ideal for those who do not have such a brightly developed figurative thinking, but everything is in order with its associative form.

The most striking examples of versification in order to fix in memory the order of the planets are the following:

"The Bear Comes Out for Raspberries - The Lawyer Managed to Escape the Lowlands";
"We All Know: Yulia's Mom Got on Stilts in the Morning."

You can, of course, not add up the rhyme, but simply pick up words that begin with the first letters in the names of each of the planets. A little advice: in order not to confuse Mercury and Mars, starting with the same letter, put the first syllables at the beginning of your words - ME and MA, respectively.

For example: In some places, Golden Cars were seen, Yulili As if Seeing Us.

You can come up with such proposals indefinitely - as long as your imagination is enough. In a word, try, train, remember ...

Article author: Mikhail Sazonov

> Planets

Explore everything planets of the solar system in order and learn the names, new scientific facts and interesting features surrounding worlds with photos and videos.

There are 8 planets in the solar system: Mercury, Venus, Mars, Earth, Jupiter, Saturn, Uranus and Neptune. The first 4 belong to the inner solar system and are considered terrestrial planets. Jupiter and Saturn major planets The solar system and representatives of gas giants (huge and filled with hydrogen and helium), and Uranus and Neptune are ice giants (large and represented by heavier elements).

Previously, Pluto was considered the ninth planet, but since 2006 it has moved into the category of dwarf planets. This dwarf planet was first discovered by Clyde Tomb. Now it is one of the largest objects in the Kuiper belt - a cluster of icy bodies on the outer edge of our system. Pluto lost its planetary status after the IAU (International Astronomical Union) revised the concept itself.

According to the decision of the IAU, a planet of the solar system is a body that performs an orbital passage around the Sun, endowed with sufficient mass to form in the form of a sphere and clear the area around it from foreign objects. Pluto could not meet the last requirement, and therefore became a dwarf planet. Other similar objects include Ceres, Makemake, Haumea, and Eridu.

With a small atmosphere, harsh surface features and 5 satellites, Pluto is considered the most complex dwarf planet and one of amazing planets in our solar system.

But scientists do not lose hope of finding the mysterious Ninth Planet - after they announced in 2016 a hypothetical object that affects gravity on bodies from the Kuiper belt. In terms of parameters, it is 10 times the mass of the Earth and 5,000 times more massive than Pluto. Below is a list of the planets of the solar system with photos, names, descriptions, detailed characteristics and interesting facts for children and adults.

Variety of planets

Astrophysicist Sergei Popov on gas and ice giants, binary star systems and single planets:

Hot planetary coronas

Astronomer Valery Shematovich on the study of gas shells of planets, hot particles in the atmosphere and discoveries on Titan:

Diameter relative to Earth	Mass, relative to the Earth	Orbital radius, a. e.	Orbital period, Earth years	Day, relative to the earth	Density, kg/m³	satellites
0,382	0,06	0,38	0,241	58,6	5427	No
0,949	0,82	0,72	0,615	243	5243	No
1,0	1,0	1,0	1,0	1,0	5515	1
0,53	0,11	1,52	1,88	1,03	3933	2
0,074	0,000013	2,76	4,6	0,46	~2000	No
11,2	318	5,20	11,86	0,414	1326	67
9,41	95	9,54	29,46	0,426	687	62
3,98	14,6	19,22	84,01	0,718	1270	27
3,81	17,2	30,06	164,79	0,671	1638	14
0,098	0,0017	39,2	248,09	6,3	2203	5
0,032	0,00066	42,1	281,1	0,03	~1900	2
0,033	0,00065	45,2	306,28	1,9	~1700	No
0,1	0,0019	68,03	561,34	1,1	~2400	1

Terrestrial planets of the solar system

The first 4 planets from the Sun are called terrestrial planets because their surface is rocky. Pluto also has a solid surface layer (frozen), but it belongs to the dwarf type planets.

Gas giant planets of the solar system

4 gas giants live in the outer solar system, as they are quite huge and gaseous. But Uranus and Neptune are different because they more ice. Therefore, they are also called ice giants. However, all gas giants have one thing in common: they are all made up of hydrogen and helium.

The IAU put forward the definition of a planet:

The object must revolve around the sun;
Have enough mass to take the shape of a ball;
Clear your orbital path from foreign objects;

Pluto could not meet the latter requirement, as it shares an orbital path with a huge number of bodies from the Kuiper belt. But not everyone agreed with the definition. However, dwarf planets such as Eris, Haumea and Makemake appeared on the scene.

Ceres also lives between Mars and Jupiter. She was noticed in 1801 and considered a planet. Some still consider it the 10th planet of the solar system.

Dwarf planets of the solar system

Formation of planetary systems

Astronomer Dmitry Wiebe about stone planets and giant planets, the diversity of planetary systems and hot Jupiters:

Solar system planets in order

Below are the characteristics of the 8 major planets of the solar system in order from the sun:

The first planet from the Sun is Mercury

Mercury is the first planet from the Sun. It rotates in an elliptical orbit with a distance of 46-70 million km from the Sun. It spends 88 days on one orbital span, and 59 days on an axial span. Due to the slow rotation, a day spans 176 days. The axial tilt is extremely small.

With a diameter of 4887 km, the first planet from the Sun reaches 5% of the earth's mass. Surface gravity - 1/3 of the earth. The planet is practically devoid of an atmospheric layer, so it is hot during the day and freezes at night. The temperature mark fluctuates between +430°C and -180°C.

There is a crater surface and an iron core. But the magnetic field is inferior to the earth. Initially, radars indicated the presence of water ice at the poles. The Messenger confirmed the assumptions and found deposits at the bottom of the craters, which are all the time immersed in shadow.

The first planet from the Sun is located close to the star, so it can be seen before dawn and just after sunset.

Name: the messenger of the gods in the Roman pantheon.
Diameter: 4878 km.
Orbit: 88 days.
Day length: 58.6 days.

Second planet from the Sun - Venus

Venus is the second planet from the Sun. Travels in an almost circular orbit at a distance of 108 million km. It comes closest to the Earth and can reduce the distance to 40 million km.

It spends 225 days on an orbital path, and an axial rotation (clockwise) lasts 243 days. Day covers 117 earth days. The axial tilt is 3 degrees.

In diameter (12100 km), the second planet from the Sun almost converges with the earth and reaches 80% of the earth's mass. The gravity indicator is 90% of the earth. The planet has dense atmospheric layer, where the pressure is 90 times higher than the earth. The atmosphere is filled with carbon dioxide with thick sulfur clouds, which creates a powerful greenhouse effect. It is because of this that the surface warms up by 460 ° C (the hottest planet in the system).

The surface of the second planet from the Sun is hidden from direct observation, but scientists managed to create a map using radar. Sheltered by large volcanic plains with two huge continents, mountains and valleys. There are also impact craters. A weak magnetic field is observed.

Detection: The ancients saw without the use of tools.
Name: Roman goddess responsible for love and beauty.
Diameter: 12104 km.
Orbit: 225 days.
Day length: 241 days.

Third planet from the Sun - Earth

Earth is the third planet from the Sun. It is the largest and densest of the inner planets. The orbital path is 150 million km away from the Sun. It has a single companion and developed life.

The orbital flyby takes 365.25 days, and the axial rotation takes 23 hours, 56 minutes and 4 seconds. The length of the day is 24 hours. The axial tilt is 23.4 degrees, and the diameter index is 12742 km.

The third planet from the Sun was formed 4.54 billion years ago and the Moon has been nearby for most of its existence. It is believed that the satellite appeared after a huge object crashed into the Earth and pulled material into orbit. It was the Moon that stabilized the earth's axial tilt and acts as a source of tide formation.

The satellite in diameter covers 3747 km (27% of the Earth's) and is located at a distance of 362000-405000 km. Experiencing a planetary gravitational effect, due to which it slowed down the axial rotation and fell into the gravitational block (therefore, one side is turned towards the Earth).

The planet is protected from stellar radiation by a powerful magnetic field formed by an active core (molten iron).

Diameter: 12760 km.
Orbit: 365.24 days.
Day length: 23 hours and 56 minutes.

The fourth planet from the Sun is Mars

Mars is the fourth planet from the Sun. The red planet moves along an eccentric orbital path - 230 million km. It spends 686 days on one flight around the Sun, and an axial rotation - 24 hours and 37 minutes. It is tilted at 25.1 degrees and a day lasts 24 hours and 39 minutes. The slope resembles the Earth, so it has seasons.

The diameter of the fourth planet from the Sun (6792 km) is half that of the earth, and the mass reaches 1/10 of the earth. The gravity indicator is 37%.

Mars is unprotected as a magnetic field, so the original atmosphere was destroyed by the solar wind. The devices recorded the outflow of atoms into space. As a result, the pressure reaches 1% of the earth's, and a thin atmospheric layer is represented by 95% carbon dioxide.

The fourth planet from the Sun is extremely frosty, where temperatures drop to -87°C in winter and rise to -5°C in summer. It is a dusty place with gigantic storms capable of covering the entire surface.

Detection: The ancients saw without the use of tools.
Title: Roman god of war.
Diameter: 6787 km.
Orbit: 687 days.
Day length: 24 hours and 37 minutes.

Fifth planet from the Sun - Jupiter

Jupiter is the fifth planet from the Sun. In addition, in front of you is the largest planet in the system, which is 2.5 times more massive than all the planets and covers 1/1000 of the solar mass.

It is 780 million km away from the Sun and spends 12 years on an orbital path. It is filled with hydrogen (75%) and helium (24%) and may have a rocky core immersed in liquid metallic hydrogen with a diameter of 110,000 km. The total planetary diameter is 142,984 km.

In the upper layer of the atmosphere there are 50-kilometer clouds, represented by ammonia crystals. They are in lanes moving at different speeds and latitudes. The Great Red Spot, a large-scale storm, seems noteworthy.

The fifth planet from the Sun spends 10 hours on an axial rotation. This is a rapid speed, which means that the equatorial diameter is 9000 km more than the polar one.

Detection: The ancients saw without the use of tools.
Name: the main god in the Roman pantheon.
Diameter: 139822 km.
Orbit: 11.9 years.
Day length: 9.8 hours.

The sixth planet from the Sun is Saturn

Saturn is the sixth planet from the Sun. Saturn is in the 2nd position in terms of scale in the system, exceeding the earth's radius by 9 times (57,000 km) and 95 times more massive.

It is 1400 million km away from the Sun and spends 29 years on an orbital flight. Filled with hydrogen (96%) and helium (3%). May have a rocky core in liquid metallic hydrogen with a diameter of 56,000 km. The upper layers are represented by liquid water, hydrogen, ammonium hydrosulfide and helium.

The core is heated up to 11700°C and produces more heat than the planet receives from the Sun. The higher we climb, the lower the degree drops. At the top, the temperature is kept at -180°C and 0°C at a depth of 350 km.

The cloud layers of the sixth planet from the Sun resemble the picture of Jupiter, but they are fainter and wider. There is also the Great White Spot, a brief periodic storm. It spends 10 hours and 39 minutes on an axial turn, but it is difficult to give an exact figure, since there are no fixed surface features.

Detection: The ancients saw without the use of tools.
Name: god of economy in the Roman pantheon.
Diameter: 120500 km.
Orbit: 29.5 days.
Day length: 10.5 hours.

The seventh planet from the Sun is Uranus

Uranus is the seventh planet from the Sun. Uranus is a representative of the ice giants and is the 3rd largest in the system. In diameter (50,000 km) it is 4 times larger than the earth and 14 times more massive.

It is distant by 2900 million km and spends 84 years on the orbital path. Surprisingly, according to the axial tilt (97 degrees), the planet literally rotates on its side.

It is believed that there is a small rocky core around which a mantle of water, ammonia and methane is concentrated. This is followed by a hydrogen, helium and methane atmosphere. The seventh planet from the Sun is also distinguished by the fact that it does not radiate more internal heat, so the temperature mark drops to -224 ° C (the frostiest planet).

Discovery: Noticed by William Herschel in 1781.
Name: personification of the sky.
Diameter: 51120 km.
Orbit: 84 years old.
Day length: 18 hours.

Neptune is the eighth planet from the Sun. Neptune has been the official last planet in the solar system since 2006. The diameter is 49,000 km, and in terms of massiveness it is 17 times larger than the earth.

It is distant by 4500 million km and spends 165 years on an orbital flight. Due to its remoteness, only 1% of solar radiation (compared to Earth) enters the planet. The axial tilt is 28 degrees, and the rotation is completed in 16 hours.

The meteorology of the eighth planet from the Sun is more pronounced than that of Uranus, so powerful storm actions can be seen at the poles in the form of dark spots. The wind accelerates to 600 m/s, and the temperature mark drops to -220°C. The core is heated up to 5200°C.

Discovery: 1846.
Title: Roman god of water.
Diameter: 49530 km.
Orbit: 165 years.
Day length: 19 hours.

This is a small world, inferior in size to the terrestrial satellite. The orbit intersects with Neptune and in 1979-1999. it could be considered the 8th planet in terms of distance from the Sun. Pluto will remain beyond the orbit of Neptune for more than two hundred years. The orbital path is tilted to the system plane by 17.1 degrees. Frosty World visited New Horizons in 2015.

Discovery: 1930 - Clyde Tombaugh.
Title: Roman god of the underworld.
Diameter: 2301 km.
Orbit: 248 years.
Day length: 6.4 days.

The ninth planet is a hypothetical object residing in the outer system. Its gravity should explain the behavior of trans-Neptunian objects.

In the late 20th and early 21st centuries, many objects were discovered in the outer solar system. It has become clear that Pluto is only one of the largest Kuiper belt objects known to date. Moreover, at least one of the objects of the belt - Eris - is a larger body than Pluto and 27% heavier than it. In this regard, the idea arose to no longer consider Pluto as a planet. On August 24, 2006, at the XXVI General Assembly of the International Astronomical Union (IAU), it was decided to henceforth call Pluto not a "planet", but a "dwarf planet".

The material was prepared on the basis of information from open sources