Planets of the solar system. Planets of our solar system The Sun is the closest star to Earth

solar system

We all live on planet Earth, which is an integral part of the solar system. This is like our district or district in the vast galactic space. In the center is the Sun (a yellow star or yellow dwarf), around which nine planets revolve together.

The Sun is the closest star to Earth

The Sun is the only star in the Solar System; all the planets of the system, as well as their satellites and other objects, including cosmic dust, move around it. If we compare the mass of the Sun with the mass of the entire solar system, it will be about 99.866 percent.

The Sun is one of the 100,000,000,000 stars in our Galaxy and is the fourth largest among them. The closest star to the Sun, Proxima Centauri, is located four light years from Earth.

The distance from the Sun to planet Earth is 149.6 million km; light from a star reaches in eight minutes. The star is located at a distance of 26 thousand light years from the center of the Milky Way, while it rotates around it at a speed of 1 revolution every 200 million years.

They are known to every schoolchild. This is the closest to the luminary Mercury, then Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and the most distant small planet Pluto.

By earthly standards, the solar system has not just large, but huge and endless spaces. In order not to frighten themselves with crazy numbers in kilometers, experts came up with such a unit of measurement for the vast and vast expanses of space as astronomical unit. One such a. e. equal to 149.6 million km - this is the average distance of the Earth from the Sun.

A general idea of ​​the size of the entire solar system is given by the distance between the Sun and the planet Pluto. It is neither more nor less than thirty-nine astronomical units, and this is provided that the small planet is at the closest point in its orbit to the Sun - perihelion. If Pluto, moving along its orbit, hits aphelion - the farthest point of the orbit, then the distance increases to forty-nine astronomical units.

They picked up a coffee pot - a gamma quantum particle separated from the Sun and rushed towards the Earth. They put an empty cup on the table, brushed the crumbs from the eaten confectionery product onto the floor - the messenger of the yellow star hit the cutlery and, being reflected, merged with many other reflected particles. The amount of brightness of such reflected sunlight is called albedo.

Albedo is a value characterizing the reflectivity of the surface of a body; the ratio (in%) of the reflected flux of solar radiation to the flux of incident radiation.

For reference, it should be noted that light takes six hours to reach Pluto. If we take intergalactic spaces, then there are completely different measurement criteria. Huge distances, say to our respected neighbor Andromeda, are already measured in light years and parsecs.

Light year (light year, ly) is a non-system unit of length equal to the distance traveled by light in one year.

A light year is equal to:

Parsec (Russian designation: pk; international: pc) is a common non-system unit of distance measurement in astronomy. The name is formed from the abbreviations of the words “parallax” and “second” - a parsec is equal to the distance to an object whose annual trigonometric parallax is equal to one arcsecond.

Parsec: According to an equivalent definition, a parsec is the distance from which a segment of one astronomical unit in length (substantially equal to the mean radius of the Earth's orbit), perpendicular to the line of sight, is visible at an angle of one arcsecond (1″).

1 pc = A. e. ≈ 206,264.8 a. e. = 3.0856776·1016 m = 30.8568 trillion km (petameters) = 3.2616 light years in other words, this is 30.8568 trillion km.

Multiple units are also used: kiloparsec (kpc), megaparsec (Mpc), gigaparsec (Gpc). Submultiples are generally not used, since astronomical units are used instead.

What is the brightness of the stars?

The brightness of stars is determined using a scale that was first proposed by the ancient Greek astronomer Hipparchus in 150 BC.

The brightest star known at that time was Antares in the constellation Scorpio, to which Hipparchus assigned the first degree of brightness. He assigned the sixth degree of brightness to the least bright star he knew. Today, astronomers using telescopes and binoculars can see much dimmer stars than Hipparchus saw. The further away a star is, the dimmer and smaller it appears, regardless of its actual brightness. The brightest star in our sky, Sirius, was called the Dog Star in ancient times because it belonged to the constellation Canis Major. In ancient Greece, this constellation was also called the Dog of Orion, the mythological hunter.

All nine planets get along well with each other. Every curious pilgrim who has the opportunity to go to the North Pole, and who also takes a telescope with him, can be convinced of this. Shivering from the frost and admiring the beauty of the starry sky, he will easily discover that the planets of the solar system move counterclockwise, and even lie in approximately the same plane. The plane of the orbit of the planet Earth is always taken as a basis, which coincides with the cross-section of the celestial sphere and is called the ecliptic plane.

Further observations will delight the traveler’s eye and bring peace to his soul: all nine cosmic bodies rotate in strictly designated spaces in elliptical orbits, so they cannot crash into each other. True, it will be difficult for our newly minted astronomer to notice the main thing: the planets are divided into two groups, and between them there is an asteroid belt.

The first group includes the four planets located closest to the Sun. These are Mercury, Venus, Earth and Mars. They have many common characteristics: approximately the same density (on average 4.5 g/cm³), small sizes, slow rotation around their axis, and a small number of natural satellites. Only the Earth has them - the Moon and Mars - Phobos and Deimos. These four planets are called terrestrial planets.

terrestrial planets

But beyond the asteroid belt the picture is completely different. The other four planets rule there: Jupiter, Saturn, Uranus and Neptune. They are also similar in density (on average 1.2 g/cm³), are huge in size, rotate quickly around their axis and are surrounded by a large number of satellites. In addition, they lack a solid surface, and their atmospheres are saturated with hydrogen and helium. These four planets are called gas giants.

Gas giants: Jupiter, Saturn, Uranus, Neptune

Standing apart is the small and neat Pluto, which in its characteristics is similar to the planets of the first group. True, his status has changed quite recently. Now it is called a dwarf planet: this is what the International Astronomical Union decided. To be honest, this verdict did not receive unanimous support among scientists, and many still consider Pluto to be the ninth planet of the solar system. Pluto, along with its three satellites Charon, Hydra and Nikto, is in the so-called Kuiper belt, which begins beyond the orbit of Neptune.

This is a huge area, twenty times larger than the asteroid belt. Here, in the complete darkness of the cosmic abyss, there are many unknown and mysterious objects. It is estimated that there are at least forty thousand of them. More recently, several dwarf planets have been discovered in this world far from Earth. They are called Eris, Ceres, Haumea and Makemake.

In addition to the planets and the Sun itself, the Solar System also contains smaller cosmic formations. These are the already mentioned asteroids, comets and meteorites. The biggest ones are of course asteroids.

Particularly large specimens reach thousands of kilometers in diameter. They are also called minor planets that orbit the Sun between the orbits of Mars and Jupiter.

Asteroids are divided into three classes: carbonaceous, siliceous and metallic. Their main difference for the human eye is color. As the name implies, carbonaceous asteroids contain a lot of carbon and therefore have a relatively dark surface. They are the vast majority in the solar system. Seventy-five percent of small planets belong to this class of C-type.

Other asteroids (siliceous) are S-type and are a mixture of iron-nickel ore and silicates. In contrast to their dull counterparts, they are very bright. In quantitative terms, there are much fewer of them - seventeen percent. All other minor planets are metallic asteroids. They consist of iron and nickel and belong to the M-type.

The very first asteroid discovered in space was named Ceres. Its shape is spherical, and its equatorial diameter is 975 km. The largest asteroids also include Vesta, Europa, David, Camilla and many others.

In total, there are currently about one hundred thousand asteroids.

Now let's talk about meteorites. Here we need to touch on terminology. For many, it will probably be an unpleasant surprise to learn that everything that can possibly fall is falling onto our beloved blue planet from outer space. These include asteroids lost in space, old comets, and other small and solid formations. So - any solid body of cosmic origin that fell to Earth is called meteorite

Meteorite in the Earth's atmosphere

Meteorites fall on the earth's expanses in continuous rain. Experts have calculated that 5-6 tons of cosmic solids enter the atmosphere of our planet per day. Two thousand tons are produced per year. Fortunately, not all of them reach the surface of the earth and water, since the laws of physics reliably protect our lives from cosmic lawlessness.

First of all, I need to say thank you. ablation. This is a mechanism for reducing the mass of small celestial bodies as they pass through dense layers of the atmosphere.

When a meteorite enters the atmosphere of planet Earth, its speed is approximately 25 km/s. Such swiftness of an uninvited guest from space leads to its heating and glow. Due to ablation, the mass of the extraterrestrial body decreases sharply. Small formations burn in the upper layers of the atmosphere without a residue; Pitiful grains reach the ground. So, out of hundreds of tons of different-sized rocks and iron rocks, only grams of these cosmic substances fall onto the surface of the blue planet.

But this is a small matter. A multi-ton colossus can cause innumerable disasters to people if it finds the opportunity to fall from heaven onto the fertile and dear expanses of Mother Earth. Fortunately, this happens very, very rarely.

And finally comets. These are some of the most mysterious and enigmatic cosmic bodies roaming the expanses of the solar system. They are born and live in a distant place, covered in impenetrable darkness, Oort cloud, located beyond the Kuiper belt. From there they fly, cross the orbits of the planets, approach the Sun, go around it, return along the opposite trajectory and disappear into the deserted silence of the boundless Space.

Each comet appears within the visibility of earthly telescopes after a strictly defined time. Some of these mysterious bodies can return after 70 years, others after 150, and there are others whose appearance will have to wait about three hundred years.

Therefore, in order to somehow systematize this issue, comets were divided into short-period and long-period. Short-period are those whose period is less than 200 years. And for long-period ones, on the contrary - the period lasts more than 200 years, as their name indirectly suggests. More than two hundred of the former have now been discovered, and a little over seven hundred of the latter.

The Oort cloud region itself is purely hypothetical, that is, speculative, based on a hypothesis. The hypothesis itself is based on the probabilistic growth of the giant planets (Jupiter, Saturn). With an increase in the mass of the latter, gravitational disturbances intensify. This leads to the fact that small primary bodies (planetesimals) begin to be ejected from the ring zones (dust, small rocks) located around these planets. They create a spherical region on the outskirts of the Solar system - the Oort cloud, which is the cradle of comets.

Actually, not the entire comet is created on the distant periphery, but only its nucleus. It is an ice block made of frozen gas and other volatile substances, with solid particles interspersed with them. At first, this frozen mass looks very similar to an ordinary asteroid. But now the core passes most of the way - some eleven astronomical units remain to the Sun - and here transformations begin to occur.

If you look at this moving object from Earth, the false asteroid gradually begins to take on the appearance of a foggy speck. It is around the nucleus that a coma forms - a foggy shell. It is the result of the evaporation from the surface of an ice block of frozen gas and other volatile substances that make up the solid base of the comet.

Gradually the coma begins to lengthen. It develops a small tail, which becomes quite visible at a distance of 3-4 astronomical units from the Sun.

Comet

But the comet turns out to be very close to the star (no more than 2 AU). Its tail stretches out and acquires enormous dimensions due to the fact that sunlight knocks gas particles out of the coma and throws them far back. This long, smoky tail can stretch for hundreds of thousands and even a million kilometers.

Many comets have two tails: gas and dust. The gas tail is a luminous plume, as it is ionized by ultraviolet rays and streams of particles that bombard it from the solar surface. The dust tail scatters sunlight and looks like a long haze.

The orbits of comets, along which they go around the star, are elongated ellipses. But it is impossible to clearly define the path of passage of these cosmic bodies. The fact is that they cross the orbits of planets, and those, acting on comets using gravity, disrupt their trajectory. Therefore, it is only possible to calculate the approximate orbit of these mysterious provincials from the distant outskirts of the solar system.

Some mysterious events that occurred on planet Earth many millions of years ago are directly associated with comets. There is a theory that humanity directly owes the appearance of water and other volatile compounds to comets.

It was after their bombardment many billions of years ago that the dry soil, then far from being a blue planet, became saturated with moisture. The atmosphere, seas, oceans, rivers and lakes appeared. Complex organic compounds were also brought to our land, and the basis was laid for the emergence of the simplest organisms.

Comets are also credited with causing a powerful natural disaster 65 million years ago at the turn of the Cretaceous and Tertiary geological periods. It was at this time that dinosaurs and 70% of other living organisms that inhabited the Earth disappeared.

As supporters of this theory say, a comet nucleus (its diameter was 10 km) with a large content of iridium fell on our planet. A strong explosion occurred, releasing a huge amount of dust into the surrounding atmosphere. She covered the earth from the sun's rays. The average temperature dropped by 10-15 degrees. For a whole year, this dust hung in the air, provoking a sharp cold snap, which killed all living things. There is confirmation of this: the age of the iridium layer in geological deposits exactly corresponds to that distant time period.

There are a huge number of different theories and hypotheses that cover not only comets, but also all other bodies and formations that exist in the Solar System. Of particular interest is question about the origin of the sun and planets.

The emergence of the solar system

According to the generally accepted version, this entire well-functioning and well-functioning cosmic system was born 4.6-5 billion years ago. This accuracy is based on calculations of the amount of helium, which is the second largest component of the Sun. Our star consists of hydrogen, and the inert gas helium appears as a result of thermonuclear reactions that continuously occur in the bowels of the yellow star.

It all started with a huge cloud of interstellar dust and gas. As a result, either natural dynamics, or a shock wave resulting from the explosion of a supernova, or some other reasons, the substance of this cosmic formation became denser.

This was the impetus for gravitational collapse - the catastrophically rapid compression of massive bodies under the influence of gravitational forces. As a result, a hot core with a very high density arose. A disk-shaped gas and dust cloud formed along the edges of the core. This disk grew and reached the size of the modern solar system.

The hot core gradually shrank, decreased in size, increasing its density and temperature more and more, and eventually turned into protostar(star until thermonuclear reactions ignite). The dust, in turn, became denser and distributed in the form of a plane around the flaming core. The result was the appearance of a cosmic body, which in its shape resembled a UFO saucer.

The protostar continued to shrink, its temperature rising. Finally, it reached millions of kelvins in the center and provoked the start of thermonuclear reactions of hydrogen combustion. Helium began to be released, and the protostar passed into a new quality - it became an ordinary star (the Sun). All these cosmic transformations stretched over more than one million years.

Next came the process of planet formation. The dust layer was characterized by hydrodynamic instability and was soon replaced by dust compactions. They collided with each other, compressed - they were replaced by small solid bodies. These new formations merged into larger ones. It was they who became the gravitational centers for the formation of planets from the matter of the protoplanetary disk.

The system strived for stability, and, in the end, in the outer regions of the disk, gravitational centers formed nine planets, rotating in the same plane and in the same direction. This took about four million years. The initial formation of the solar system ended here.

Its further evolution is characterized by a change in orbits and a change in the order of the planets, and the emergence of satellites around them. This process continues now, once again proving that in Space there are no frozen forms that are not subject to gravitational interactions. They are the root cause of all long-term changes in previous states, both in the Solar System itself and in larger interstellar and intergalactic formations.

From all of the above, it is clear that humanity has not wasted time in vain over the past centuries and has created a fairly coherent theory covering all aspects of the solar system. But this is only at first glance. The true state of affairs is such that a huge number of questions, ambiguities and outright secrets have accumulated today. The answers to them are very contradictory and uncertain, and the truth is unclear and foggy.

Age of the Solar System

One of the main mysteries is age of the solar system. The official version has already been mentioned, which calls the time interval 4.6-5 billion years. But it explains little if we consider it from the point of view of the methodology for calculating the amount of helium, which is the result of thermonuclear reactions and is currently present in the Sun.

The fact is that estimating the amount of this inert gas is not an obvious quantity. Some claim that it contains 34% of the total solar mass, while others say 27%. The spread is seven percent. Accordingly, the time interval can vary from 5 to 6.5 billion years, and even then only from the moment when the protostar turned into the Sun.

At present, there is not even a clear idea of ​​the thermonuclear reactions that occur in the bowels of a yellow dwarf. There are two proposed cycles for the conversion of hydrogen into helium - the proton (hydrogen) and carbon (Bethe cycle).

Experts are more inclined to the first cycle, which includes three reactions: a deuterium nucleus is formed from a hydrogen nucleus, then a helium isotope nucleus with an atomic mass of three is formed from a deuterium nucleus, and the process ends with a stable helium isotope with an atomic mass of four.

Age of planet Earth

What is really more or less clear and not subject to criticism is this age of planet Earth and its satellite Moon. Here the concept of radioactivity is taken as a basis. It refers to the transformation of atomic nuclei into other nuclei, accompanied by the emission of various particles and electromagnetic radiation.

In this case, the uranium atom is taken as the basis. It is unstable, emits energy and is converted over time into a lead atom, which is a stable element. Provided that the rate of nuclear decay is absolutely constant, one can easily calculate the time period during which one element is replaced by another.

Any mass of uranium (isotope) has a certain number of atoms. The replacement of half of the uranium atoms by a similar number of lead atoms occurs in 4.5 billion years - the half-life. The complete transformation of uranium into lead takes 9 billion years.

The oldest mineral on Earth was found in Australia; its age was determined to be 4.2 billion years. Meteorites that fall on the blue planet are also far from young - they are usually 4.5-4.6 billion years old. Thanks to modern scientific achievements (the American Apollo expedition, the Soviet automatic interplanetary station Luna-16), samples of lunar soil were delivered to Earth.

It turned out to be not the first freshness. Its years range from 4 to 4.5 billion years.

Many immediately seized on these figures, categorically declaring that the existence of the entire solar system also lies in this time interval. Nobody argues - the Earth and the Moon live according to the same laws as other cosmic bodies. But who can give an absolute guarantee that in the near future a mineral will not be found in the depths of our planet, the age of which will be, for example, 8 billion years, or a sample of an equally venerable age will be delivered from the Moon. It is also not known what the soil of other planets, colleagues of the old Earth, is like.

In a word, the question of the maturity of the Solar system still remains open. Most likely, a clear and precise answer will not be found in the near future. But the truth is always on the side of the persistent and inquisitive. Some time will pass, humanity will master the stock of new knowledge, and then it will wonder how it could not have seen the answers that were practically on the surface before..

The article was written by ridar-shakin

• Space communication has been established between the nine planets of the solar system. Scheduled rockets fly on the following routes:

• Earth-Mercury

• Pluto-Venus

• Earth – Pluto

• Pluto – Mercury

• Mercury – Venus

• Uranus – Neptune

• Neptune – Saturn

• Saturn – Jupiter

• Jupiter – Mars

• Mars – Uranus

• Is it possible to fly on regular rockets from Earth to Mars?

Solution:

The concept of “Graph” A graph is a diagram consisting of points and segments connecting these points. Points are the vertices of the graph. Segments are the edges of the graph.

Problem 2

• Arkady, Boris, Vladimir, Grigory and Dmitry shook hands when they met (each shook hands with each other once).

• How many handshakes were done?

Solution:

• Let each of the young people correspond to a point on the plane, named after the first letter of the name, and the handshakes made are a segment or a curved line that will connect the points corresponding to the names.

• (zero graph)

(incomplete graph)

(full graph)

Sciences based on knowledge GRAPH THEORIES:

• Medicine

• Cybernetics

• Informatics

• Chemistry

• Physics

• Transport

• Construction

• Applied Mathematics

• Economy

Leonard Euler

Draw shapes with one stroke

Label the intersection points, and in parentheses write how many lines come out of one or another intersection point.

• In what case is it possible to outline figures without lifting the pencil from the paper and without drawing a single line twice, and in what case is it not?

Conclusion:

• Conclusion:

• - If all the vertices of the graph are even, then it is possible to draw a figure, and you can start from any vertex.

• -If two of these vertices are odd, then you can draw a figure, but you just need to start at one of these two odd vertices and end at the second odd vertex.

Is it possible to take a walk by crossing each bridge only once?

Task

• A fly climbed into a sugar jar. The jar has the shape of a cube. Can a fly sequentially go around all 12 edges of a cube without going over the same edge twice? Jumping and flying from place to place is not allowed.

Planets There is space communication between the nine planets of the solar system. Regular rockets fly on the following routes: Earth - Mercury; Pluto - Venus; Earth - Pluto; Pluto - Mercury; Mercury - Vienna; Uranus - Neptune; Neptune - Saturn; Saturn – Jupiter; Jupiter - Mars and Mars - Uranus. Is it possible to fly on regular rockets from Earth to Mars? Space communication has been established between the nine planets of the solar system. Regular rockets fly on the following routes: Earth - Mercury; Pluto - Venus; Earth - Pluto; Pluto - Mercury; Mercury - Vienna; Uranus - Neptune; Neptune - Saturn; Saturn – Jupiter; Jupiter - Mars and Mars - Uranus. Is it possible to fly on regular rockets from Earth to Mars?

Telephones There are 15 telephones in the town of Malenky. Is it possible to connect them with wires so that each phone is connected to exactly five others? There are 15 telephones in the town of Malenky. Is it possible to connect them with wires so that each phone is connected to exactly five others?

Cities There are 15 cities in the country of Seven, each city is connected by roads to at least seven others. Prove that it is fashionable to get from every city to any other. There are 15 cities in the country of Seven, each city is connected by roads to at least seven others. Prove that it is fashionable to get from every city to any other.

How many roads? There are 100 cities in the state, each with 2 roads, except for the capital, where 5 roads go, and the city of Gorny, where there is only one road. How many roads are there in the state? There are 100 cities in the state, each with 2 roads, except for the capital, where 5 roads go, and the city of Gorny, where there is only one road. How many roads are there in the state?

Who plays Tyapkin-Lyapkin The school drama club decided to stage Gogol's The Inspector General. And then a heated argument broke out. It all started with Lyapkin-Tyapkin. The school drama club decided to stage Gogol's The Inspector General. And then a heated argument broke out. It all started with Lyapkin-Tyapkin. I will be Lyapkin-Tyapkin! – Gena stated decisively. I will be Lyapkin-Tyapkin! – Gena stated decisively. No, I’ll be Lyapkin-Tyapkin,” Dima objected, “from early childhood I dreamed of bringing this image to life on stage.” No, I’ll be Lyapkin-Tyapkin,” Dima objected, “from early childhood I dreamed of bringing this image to life on stage.” Well, okay, I agree to give up this role if they let me play Khlestakov,” Gena showed generosity. Well, okay, I agree to give up this role if they let me play Khlestakov, - Gena showed generosity.... And for me - Osipa - Dima did not give in to him in generosity.... And for me - Osipa - he did not give in to him in generosity Dima. “I want to be Strawberry or Mayor,” said Vova. “I want to be Strawberry or Mayor,” said Vova. No, I will be the Mayor,” Alik and Borya shouted in unison. “Or Khlestakov,” they added at the same time. No, I will be the Mayor,” Alik and Borya shouted in unison. “Or Khlestakov,” they added at the same time. Will it be possible to distribute the roles so that the performers are satisfied? Will it be possible to distribute the roles so that the performers are satisfied?

Favorite cartoons Once upon a time there lived one friendly family: mother, father and son. They loved to do everything together. But they loved different cartoons: “Well, wait a minute!”, “Pokemon”, “Tom and Jerry”. Determine what cartoon each of them likes, if mom, dad and a fan of the Pokemon cartoon never lose heart, and dad and a fan of the Tom and Jerry cartoon do exercises in the morning? Once upon a time there lived a friendly family: mother, father and son. They loved to do everything together. But they loved different cartoons: “Well, wait a minute!”, “Pokemon”, “Tom and Jerry”. Determine what cartoon each of them likes, if mom, dad and a fan of the Pokemon cartoon never lose heart, and dad and a fan of the Tom and Jerry cartoon do exercises in the morning?

Via Gra There are three girls singing in the Via Gra group: a blonde, a redhead and a brunette. In the “Diamonds” video, the girls wear white, red and black dresses. It’s interesting,” the brunette noted, “that the colors of our hair don’t match our dresses.” There are three girls singing in the Via Gra group: a blonde, a redhead and a brunette. In the “Diamonds” video, the girls wear white, red and black dresses. It’s interesting,” the brunette noted, “that the colors of our hair don’t match our dresses.” “That’s true, but your dress would suit me,” confirmed the girl in a white dress. “That’s true, but your dress would suit me,” confirmed the girl in a white dress. What dress was each girl wearing? What dress was each girl wearing?

The planets of the Solar System are arranged in order as follows:
1 - Mercury. The smallest real planet in the solar system
2 - Venus. The description of hell was taken from her: terrible heat, sulfur vapors and the eruptions of many volcanoes.
3 - Earth. The third planet in order from the Sun, our home.
4 - Mars. The most distant of the terrestrial planets in the Solar System.
Then there is the Main Asteroid Belt, where the dwarf planet Ceres and the minor planets Vesta, Pallas, and others are located.
Next in order are the four giant planets:
5 - Jupiter. The largest planet in the solar system.
6 - Saturn with its famous rings.
7 - Uranium. The coldest planet.
8 - Neptune. It is the farthest "real" planet in order from the Sun.
Here's what's more interesting:
9 - Pluto. A dwarf planet that is usually mentioned after Neptune. But Pluto's orbit is such that it is sometimes closer to the Sun than Neptune. For example, this was the case from 1979 to 1999.
No, Neptune and Pluto cannot collide :) - their orbits are such that they do not intersect.
The order of the planets of the solar system in the photo:

How many planets are there in the solar system

How many planets are there in the solar system? This is not so easy to answer. For a long time it was believed that there are nine planets in the solar system:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

But, on August 24, 2006, Pluto ceased to be considered a planet. This was caused by the discovery of the planet Eris and other small planets of the solar system, in connection with which it was necessary to clarify which celestial bodies can be considered planets.
Several characteristics of “real” planets were identified and it turned out that Pluto does not fully satisfy them.
Therefore, Pluto was relegated to the category of dwarf planets, which includes, for example, Ceres, the former number 1 asteroid in the Main Asteroid Belt between Mars and Jupiter.

As a result, when trying to answer the question of how many planets are in the solar system, the situation became even more confused. Because in addition to the “real” ones, dwarf planets have now also appeared.
But there are also small planets, which were called large asteroids. For example Vesta, asteroid number 2 in the mentioned Main Asteroid Belt.
Recently, the same Eris, Make-Make, Haumea and several other small ones have been discovered planets of the solar system, data about which is insufficient and it is unclear whether they should be considered dwarf or small planets. Not to mention that some small asteroids are mentioned in the literature as minor planets! For example, the asteroid Icarus, whose size is only about 1 kilometer, is often referred to as a minor planet...
Which of these bodies should be taken into account when answering the question “how many planets are there in the solar system”???
In general, “we wanted the best, but it turned out as always.”

It is curious that many astronomers and even ordinary people come out “in defense” of Pluto, continuing to consider it a planet, sometimes organizing small demonstrations and diligently promoting this idea on the Internet (mainly abroad).

Therefore, when answering the question “how many planets are there in the solar system,” the easiest way is to briefly say “eight” and not even try to discuss anything... otherwise you will immediately discover that there is simply no exact answer :)

Giant planets - the largest planets in the solar system

There are four giant planets in the solar system: Jupiter, Saturn, Uranus and Neptune. Because these planets are located outside the Main Asteroid Belt, they are called the "outer" planets of the solar system.
In terms of size, two pairs clearly stand out among these giants.
The largest giant planet is Jupiter. Saturn is quite a bit inferior to him.
And Uranus and Neptune are sharply smaller than the first two planets and they are located further from the Sun.
Look at the comparative sizes of the giant planets relative to the Sun:

The giant planets protect the inner planets of the solar system from asteroids.
Without these bodies in the solar system, our Earth would be hit by asteroids and comets hundreds of times more often!
How do giant planets protect us from the falls of uninvited guests?

You can learn more about the largest planets in the solar system here:

Terrestrial planets

The terrestrial planets are the four planets of the solar system that are similar in size and composition: Mercury, Venus, Earth and Mars.
Since one of them is the Earth, all these planets are classified as the terrestrial group. Their sizes are very similar, and Venus and Earth are generally almost the same. Their temperatures are relatively high, which is explained by their proximity to the Sun. All four planets are formed by rocks, while the giant planets are gas and ice worlds.

Mercury is the closest planet to the Sun and the smallest planet in the Solar System.
It is generally accepted that Mercury is very hot. Yes, that's right, the temperature on the sunny side can reach +427°C. But, there is almost no atmosphere on Mercury, so on the night side it can reach -170°C. And at the poles, due to the low Sun, a layer of underground permafrost is generally assumed...

Venus. For a long time it was considered the “sister” of the Earth, until Soviet research stations descended on its surface. It turned out to be real hell! Temperature +475°C, pressure of almost a hundred atmospheres and an atmosphere of toxic compounds of sulfur and chlorine. To colonize it, you will have to try very hard...

Mars. The famous red planet. It is the most distant terrestrial planet in the solar system.
Like Earth, Mars has satellites: Phobos and Deimos
It is generally a cold, rocky and dry world. Only at the equator at noon can it warm up to +20°C, the rest of the time there is severe frost, down to -153°C at the poles.
The planet does not have a magnetosphere and cosmic radiation mercilessly irradiates the surface.
The atmosphere is very rarefied and not suitable for breathing, however, its density is enough for powerful dust storms to sometimes occur on Mars.
Despite all the shortcomings. Mars is the most promising planet for colonization in the solar system.

More information about the terrestrial planets is described in the article The largest planets of the solar system

The largest planet in the solar system

The largest planet in the solar system is Jupiter. It is the fifth planet from the Sun, its orbit lies beyond the Main Asteroid Belt. Look at the size comparison between Jupiter and Earth:
Jupiter's diameter is 11 times larger than Earth's, and its mass is 318 times greater. Due to the large size of the planet, parts of its atmosphere rotate at different speeds, so the belts of Jupiter are clearly visible in the image. Below on the left you can see the famous Great Red Spot of Jupiter - a huge atmospheric vortex that has been observed for several centuries.

The smallest planet in the solar system

Which planet is the smallest planet in the solar system? This is not such a simple question...
Today it is generally accepted that the smallest planet in the solar system is Mercury, which we mentioned a little above. But, you already know that until August 24, 2006, Pluto was considered the smallest planet in the solar system.

More attentive readers may recall that Pluto is a dwarf planet. And there are five of them known. The smallest dwarf planet is Ceres, with a diameter of about 900 km.
But that's not all...

There are also so-called minor planets, the size of which starts at only 50 meters. Both the 1-kilometer Icarus and the 490-kilometer Pallas fall under this definition. It is clear that there are many of them, and it is difficult to choose the smallest one due to the complexity of observations and calculation of sizes. So, when answering the question “what is the name of the smallest planet in the solar system,” it all depends on what exactly is meant by the word “planet.”

Planets of the Solar System

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

Pluto was removed from the planet category in 2006. because There are objects in the Kuiper Belt that are larger/equal in size to Pluto. Therefore, even if we take it as a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size as Pluto.

By MAC definition, 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 planets 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, equated to an earthly year for ease of understanding, is 88 days, while Mercury manages to rotate around its own axis only one and a half times. Thus, his day lasts approximately 59 Earth days. For a long time it was believed that this planet always turned the same side to the Sun, since periods of its visibility from Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the ability to use radar research and conduct 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, image from the MESSENGER spacecraft

Its proximity to the Sun is the reason why Mercury is subject to the largest temperature changes among 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 were detected in the atmosphere. There is a theory that it was previously a satellite of Venus, but so far this remains unproven. It does not have its own satellites.

Venus

The second planet from the Sun, the atmosphere 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 the 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 quantities.

Venus in the UV spectrum

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

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 have developed. At least life as we know it. The radius of the Earth is 6371 km and, unlike other celestial bodies in our system, more than 70% of its surface is covered with water. The rest of the space is occupied by 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 changes in the landscape. The speed of the planet moving along it is 29-30 km/sec.

Our planet from space

One revolution around its axis takes almost 24 hours, and a complete passage through the orbit lasts 365 days, which is much longer in comparison with its closest neighboring planets. The Earth's day and year are also accepted as a standard, but this is done only for the convenience of perceiving time periods on other planets. The Earth has one natural satellite - the Moon.

Mars

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

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

The radius is almost half that of 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 that 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 satellite the Moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from falling meteorites, so it, like the Moon, is covered with craters. The day side of Mercury gets very hot from the Sun, while on the night side the temperature drops hundreds of degrees below zero. There is ice in the craters of Mercury, which are located at the poles. Mercury completes one revolution around the Sun every 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 by a thick and toxic atmosphere that creates a strong greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the powerful 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 a way that made life possible.

• Mars

  Although details of the surface of Mars are difficult to see from Earth, observations through a telescope indicate that Mars has seasons and white spots at the poles. For decades, people believed that the bright and dark areas on Mars were patches of vegetation, that Mars might be a suitable place for life, and that water existed in the polar ice caps. When the Mariner 4 spacecraft arrived at Mars in 1965, many scientists were shocked to see photographs of the murky, cratered planet. Mars turned out to be a dead planet. More recent missions, however, have revealed that Mars holds many mysteries that remain to be solved.

• Jupiter

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

• Saturn

  Saturn is the farthest of the five planets known before the invention of the telescope. Like Jupiter, Saturn is composed primarily of hydrogen and helium. Its volume is 755 times greater than 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 using 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

  Distant Neptune rotates almost 4.5 billion kilometers from the Sun. It takes him 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 the orbit of Neptune for about 20 years out of 248 during which it makes one revolution around the Sun.

• Pluto

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

Planets are giants

There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are located in the outer solar system. They are distinguished by 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. The year on Jupiter is not the longest in the solar system, lasting 4333 Earth days (less than 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 planet’s orbit, you need a fairly accurate and clear model of the solar system. The largest of them are Callisto, Ganymede, Io and Europa. Moreover, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% greater 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 in the solar system. In comparison with other planets, it is most similar to the Sun in the composition of chemical elements. The radius of the surface 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 much 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 in size, but no less famous are 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 others.

For a long time, the rings on Saturn were considered a unique phenomenon unique to it. Only recently it was established that all gas giants have rings, but in others they 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.