Lecture: solar system: terrestrial planets and giant planets, small bodies of the solar system
The solar system consists of various kinds of bodies. The main one, of course, is the sun. But if you do not take it into account, the planets are considered the main elements of the solar system. They are the second most important elements after the sun. The solar system itself bears this name due to the fact that the sun plays a key role here, since all the planets revolve around the sun.
Terrestrial planets
Currently, there are two groups of planets in the Solar System. The first group is the terrestrial planets. These include Mercury, Venus, Earth, and also Mars. IN this list they are all listed based on the distance from the Sun to each of these planets. They got their name due to the fact that their properties are somewhat reminiscent of the characteristics of planet Earth. All terrestrial planets have a solid surface. The peculiarity of each of these planets is that they all rotate differently around their own axis. For example, for the Earth, one complete rotation occurs within a day, that is, 24 hours, while for Venus, a complete rotation occurs in 243 Earth days.
Each of the terrestrial planets has its own atmosphere. It varies in density and composition, but it definitely exists. For example, in Venus it is quite dense, while in Mercury it is almost invisible. In fact on this moment There is an opinion that Mercury has no atmosphere at all, but in fact this is not the case. All atmospheres of terrestrial planets consist of substances whose molecules are relatively heavy. For example, the atmosphere of Earth, Venus and Mars consists of carbon dioxide and water vapor. In turn, Mercury's atmosphere consists mainly of helium.
In addition to the atmosphere, all terrestrial planets have approximately the same chemical composition. In particular, they consist predominantly of silicon compounds, as well as iron. However, these planets also contain other elements, but their number is not so large.
A feature of the terrestrial planets is that at their center there is a core of varying mass. At the same time, all nuclei are in a liquid state - the only exception is Venus.
Each of the terrestrial planets has its own magnetic fields. At the same time, on Venus their influence is almost imperceptible, while on Earth, Mercury and Mars they are quite noticeable. As for the Earth, its magnetic fields do not stand in one place, but move. And although their speed is extremely low compared to human concepts, scientists suggest that the movement of the fields may subsequently lead to a change in the magnetic belts.
Another feature of the terrestrial planets is that they have virtually no natural satellites. In particular, to date they have been discovered only near the Earth and Mars.
Giant planets
The second group of planets is called the “giant planets”. These include Jupiter, Saturn, Uranus and Neptune. Their mass significantly exceeds the mass of the terrestrial planets.
The lightest giant today is Uranus, however, its mass exceeds the mass of the earth
approximately 14 and a half times. And the heaviest planet in the solar system (with the exception of the Sun) is Jupiter.
None of the giant planets actually have their own surface, since they are all in a gaseous state. The gases that make up these planets, as they approach the center or equator, as it is called, turn into a liquid state. In this regard, one can notice the difference in the characteristics of the rotation of the giant planets around their own axis. It should be noted that the duration of a full revolution is a maximum of 18 hours. Meanwhile, each layer of the planet rotates around its axis at different speeds. This feature is due to the fact that giant planets are not solid. In this regard, their individual parts seem to be unrelated to each other.
At the center of all giant planets there is a small solid core. Most likely, one of the main substances of these planets is hydrogen, which has metallic characteristics. Thanks to this, it has now been proven that giant planets have their own magnetic field. However, in science at the moment there is very little convincing evidence and a lot of contradictions that could characterize the giant planets.
Their distinctive feature is that such planets have many natural satellites, as well as rings. In this case, rings are small clusters of particles that rotate directly around the planet and collect various types of small particles flying by.
At the moment, only 9 are officially known to science major planets. However, the terrestrial planets and giant planets include only eight. The ninth planet, which is Pluto, does not fit into any of the listed groups, since it is located at a very far distance from the Sun and is practically not studied. The only thing that can be said about Pluto is that its state is close to solid. There is currently speculation that Pluto is not a planet at all. This assumption has existed for more than 20 years, but the decision to exclude Pluto from the list of planets has not yet been made.
Small bodies of the solar system
In addition to the planets, in the Solar System there are a lot of all kinds of bodies that are relatively small in weight, which are called asteroids, comets, small planets, and so on. In general, these celestial bodies are included in the group of small celestial bodies. They differ from planets in that they are solid, relatively small in size, and can move around the Sun not only in a straight line, but also in a reverse direction. Their sizes are much smaller compared to any of the currently discovered planets. Losing cosmic gravity, small celestial bodies of the solar system fall into the upper layers earth's atmosphere, where they burn up or fall in the form of meteorites. The change in the state of bodies orbiting other planets has not yet been studied.
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Pluto - they all have small masses and sizes, their average density is several times higher than the density of water; they are able to slowly rotate around their own axes; they have a small number of satellites (Mars has two, Earth has only one, and Venus and Mercury do not have them at all).
The similarity of planets in the terrestrial group does not exclude some differences. For example, Venus rotates in the opposite direction from its movement around the Sun, and two hundred and forty-three times slower than the Earth. The period of rotation of Mercury (that is, the year of this planet) is only one-third longer than the period of its rotation around its axis.
The angle of inclination of the axis to the orbital planes of Mars and the Earth is approximately the same, but completely different for Venus and Mercury. Just like Earth, there are seasons, which means so do Mars, although almost twice as long as Earth.
Perhaps distant Pluto, the smallest of the nine planets, can also be classified as a terrestrial planet. The usual diameter of Pluto was more than two thousand kilometers. Only the diameter of Pluto’s satellite Charon is only 2 times smaller. Therefore, it is not a fact that the Pluto-Charon system, like the Earth-system, is a double planet.
Similarities and differences are also found in the atmospheres of the terrestrial planets. Venus and Mars have an atmosphere, unlike Mercury, which, however, like the Moon, is practically devoid of it. Venus has a fairly dense atmosphere, mainly consisting of sulfur compounds and carbon dioxide. The atmosphere of Mars, on the contrary, is too rarefied and very poor in nitrogen and oxygen. The pressure at the surfaces of Venus is almost a hundred times more, while at Mars it is almost a hundred and fifty times less than at the surfaces of the Earth.
The heat on the surfaces of Venus is quite high (about five hundred degrees Celsius) and remains almost the same all the time. The high temperature of the surfaces of Venus is determined by the greenhouse effect. The thick, dense atmosphere releases the rays of the Sun, but retains the heat infrared radiation, which comes from heated surfaces. Gas in the atmosphere of a terrestrial planet is in constant motion. Often during a dust storm that lasts more than one month, a large number of dust rises into the atmosphere of Mars.
- Also in ancient times The ancient Greeks noticed unusual stars in the night sky, which differed from their sisters in that they moved across the celestial sphere: they either accelerated their run, then stopped, or began to move in the other direction, and then returned to their flight again.
Heaven as perceived by ancient people
Heaven as perceived by ancient people- Astronomers called them “wanderers,” which in Greek means “planetos.”
- Now we all know from school lessons that planets are celestial bodies that orbit around
- At first, people knew only five planets, to which they gave the names of the main gods of the ancient pantheon: Mercury, Venus, Mars, Jupiter and Saturn. It is now known that there are eight of them in the solar system, and four of them are terrestrial or “Earth-like” planets, which have a solid surface on which you can walk. These are Mercury, Venus, Earth and Mars.
The earth rested on three elephants and a giant turtle
The earth rested on three elephants and a giant turtle- Jupiter, Saturn, Uranus and Neptune are giant planets. All planets, with the exception of Venus and Mercury, orbit at least one satellite. In addition to them, a huge number of other celestial bodies move in the Solar System: asteroids, dwarf planets, meteorites and comets.
Planets of the Solar System
Planets of the Solar System- In this article we will look at the terrestrial planets and the first of them is
- MERCURY.
- In Roman mythology, Mercury is the swift messenger of the gods, the patron of trade and travel.
- This is the smallest and closest planet to the Sun, which is three times closer to our luminary than the Earth, and slightly larger in size than the Moon.
- This planet orbits the Sun in just 88 Earth days, and turns around its axis very slowly: a day on Mercury is equal to 58 Earth days, i.e. lasts almost two months. Having circled the Sun twice, this planet only manages to turn around its own axis three times. On the sunny side its temperature exceeds 400 degrees, and on the other, where darkness and severe cold reign, it is 190 degrees below zero. Mercury has virtually no atmosphere.
- This planet is difficult to observe from Earth, because... she is always close to the Sun, whose bright light makes it difficult to see little Mercury. True, sometimes, at sunrise or sunset, while our star is below the horizon, it can be seen through binoculars or with the naked eye.
- VENUS.
- She got her name in honor of the ancient Roman goddess of love and beauty.
Venus
Venus- Since ancient times, it has been called the beautiful Morning and Evening Star, because This planet reaches its maximum brightness shortly before sunrise or some time after sunset. This is the second planet from our star.
- She is also called “sister of the Earth”, because they are similar in size and gravity. And yet they are completely different.
- A year on Venus lasts 225 Earth days, and a day is longer than a year and is equal to 243 Earth days. It is enveloped by the densest atmosphere among Earth-like planets, which mainly consists of carbon dioxide. It is impenetrable to telescopes and very poisonous.
- Under a thick layer of clouds of sulfuric acid, in which terrible hurricanes constantly rage, a real hell is hidden: the pressure is a hundred times higher than on Earth, and the temperature on the surface is about 500 degrees hot.
- EARTH.
- This is the third and largest of the four Earth-like planets and, of course, the most native to us.
Earth
Earth- The Earth differs from all planets in that it has air, water and life: seas and oceans, forests and mountains, flowers and trees, animals and birds, and most importantly, we, people. No wonder she was named in honor of the ancient goddess Gaia - the progenitor of all living things.
- In ancient times, the Earth rested on the backs of three whales or elephants standing on a giant turtle. Today we all know that our planet has the shape of a flattened ball and, with its movements, determines the rhythms of our lives. Rotating around its axis in 24 hours, it gives us the change of day and night, and going around the Sun in 365 days in a circle - the change of seasons.
- As we travel around the Sun on our planet, we become one year older with each revolution. Some are still at the beginning of their journey, while others have flown around it dozens of times.
- French astronomer K. Flammarion said this: “In reality, we are in the sky. The Earth is like huge ship, took us on board and rushes on a journey around the great star."
- And finally
- MARS,
- which is also included in the terrestrial planets. This is the fourth planet from the Sun and is named after the ancient Roman god of war - Mars.
Mars
Mars- And his two companions received the names Phobos and Deimos, which translated from Greek mean “fear” and “horror.”
- From Earth, Mars looks like a reddish star, which is why it is called the “red planet.”
- The reason is the orange-red tint of the surface covered with stones, sand and dust rich in iron oxide (simply rust). The atmosphere here is very rarefied and the sky has a pink tint. all because of the same red dust.
- A day on Mars lasts 24 hours 37 minutes, and the seasons correspond to those on Earth, only they last twice as long. A Martian year is equal to 689 Earth days, and the force of gravity is half that of Earth. The sun from the “red planet” looks small and dim, and therefore heats it very poorly: the temperature on the surface on a hot day does not exceed zero degrees, and at night, due to the severe frost, frozen carbon dioxide settles on the rocks. It is from this, and not from water, that the polar caps are predominantly composed.
- The famous Martian "canals" that are visible through a telescope are actually traces of soil destruction, not water flows. The highest mountain in the solar system has been discovered on Mars - the extinct Olympus volcano, 26 km high, which is almost three times higher than Earth's Everest. There is also a gigantic system of canyons up to 11 km deep, called the “Valley Marineris”, occupying a quarter of the circumference of the planet in length.
- Hopes to discover life on Mars have not yet materialized, but who knows? Today, two Mars rovers are working there: “Spirit” and “Opportunity”, and a human flight to the “red planet” is just around the corner.
Terrestrial planets: Mercury, Venus, Earth and Mars
Terrestrial planets: Mercury, Venus, Earth and Mars- When I was at school, I often wondered: “Are there planets around other stars?”
- Eat! They are called exoplanets.
- Today, astronomers know for sure about the existence of 763 exoplanets, which are located in 611 planetary systems. And another 2,326 are awaiting scientific confirmation that they actually exist.
Milky Way Galaxy
Galaxy Milky Way
- In total, our Milky Way galaxy alone may contain 100 billion exoplanets, of which 5 to 20 billion may be similar to our Earth!
- Based on materials by L. Koshman and A. Kirakosyan
Divided into 2 groups based on their planetary surfaces: gas giants and terrestrial planets. Terrestrial planets are characterized by a dense surface and, as a rule, consist of silicate compounds. There are only four such planets in the solar system: Mars, Earth, Venus and Mercury.
Terrestrial planets in the Solar System:
Mercury
Mercury is the smallest of the four Earth-like planets in the Solar System with an equatorial radius of 2439.7 ± 1.0 km. The planet is larger than moons such as Titan. However, Mercury has the second highest density (5427 grams per cubic centimeter) among the planets of the solar system, slightly inferior to Earth in this indicator. High density gives an idea of internal structure planet, which scientists believe is rich in iron. Mercury's core is believed to have the highest iron content of any planet in our system. Astronomers believe that the molten core makes up 55% of the planet's total volume. The outer layer of the iron-rich core is the mantle, which is mainly composed of silicates. The planet's rocky crust reaches 35 km in thickness. Mercury is located at a distance of 0.39 astronomical units from the Sun, which makes it the closest planet to our luminary. Due to its proximity to the Sun, the surface temperature of the planet rises to more than 400º C.
Venus
Venus is Earth's closest neighbor and one of the four terrestrial planets in the solar system. It is the second largest planet in this category with a diameter of 12,092 km; second only to Earth. However, Venus's thick atmosphere is considered the densest in the solar system, with an atmospheric pressure 92 times higher than the atmospheric pressure on our planet. The dense atmosphere consists of carbon dioxide, which has Greenhouse effect and leads to an increase in temperature on the surface of Venus to 462º C, and is . The planet is dominated by volcanic plains, covering about 80% of its surface. Venus also has numerous impact craters, some of which reach a diameter of about 280 km.
Earth
Of the four terrestrial planets, Earth is the largest with an equatorial diameter of 12,756.1 km. It is also the only planet of this group known to have a hydrosphere. Earth is the third closest planet to the Sun, located at a distance of about 150 million km (1 astronomical unit) from it. The planet also has the most high density(5.514 grams per cubic centimeter) in the Solar System. Silicate and alumina are the two compounds found in the highest concentrations in earth's crust, and they account for 75.4% of the continental crust and 65.1% of the oceanic crust.
Mars
Mars is another terrestrial planet in the Solar System, located farthest from the Sun at a distance of 1.5 astronomical units. The planet has an equatorial radius of 3396.2±0.1 km, making it the second smallest planet in our system. The surface of Mars is mainly composed of basaltic rocks. The planet's crust is quite thick and ranges from 125 km to 40 km in depth.
Dwarf planets
There are other smaller dwarf planets that have some characteristics comparable to terrestrial planets, such as having a dense surface. However, the surface of dwarf planets is formed by a sheet of ice and therefore they do not belong to this group. Examples of dwarf planets in the solar system are Pluto and Ceres.
The planets belonging to the terrestrial group - Mercury, Venus, Earth, Mars - have small sizes and masses, the average density of these planets is several times higher than the density of water; they rotate slowly around their axes; they have few satellites (Mercury and Venus have none at all, Mars has two tiny ones, Earth has one).
Similarities and differences are also revealed when studying the atmospheres of the terrestrial planets S.G. Khoroshavin. Concepts modern natural science. Course of lectures - Rostov-on-Don, 2006.
Mercury
Mercury is the fourth brightest planet: at its maximum brightness it is almost as bright as Sirius, only Venus, Mars and Jupiter are brighter than it. However, Mercury is a very difficult object to observe due to its small orbit and therefore proximity to the Sun. To the naked eye, Mercury is a point of light, but in a strong telescope it looks like a crescent or an incomplete circle. Changes in the appearance (phases) of the planet over time show that Mercury is a ball, illuminated by the Sun on one side, and completely dark on the other. The diameter of this ball is 4870 km.
Mercury slowly rotates around its axis, always facing the Sun with one side. Thus, the period of revolution around the Sun (Mercurian year) is about 88 Earth days, and the period of rotation around its axis is 58 days. It turns out that a year passes from sunrise to sunset on Mercury, that is, 88 Earth days. Indeed, the surface of Mercury is in many ways similar to the surface of the Moon, although we do not know whether there are actually seas and craters on the surface of Mercury. Mercury has a relatively high density among the planets of the Solar System - about 5.44 g/cm3. Scientists suggest that this is due to the presence of a massive metallic core (presumably made of molten iron with a density of up to 10 g/cm3, having a temperature of about 2000 K), containing more than 60% of the planet's mass and surrounded by a silicate mantle and probably a crust 60 - 100 km thick .
Venus
Venus is observed both as an “evening star” and as a “morning star” - Hesperus and Phosphorus, as it was called in the ancient world. After the sun and the Moon, Venus is the brightest celestial body, and at night objects illuminated by it can cast shadows. Venus is also the closest planet to Earth. She is even called "sister of the Earth." Indeed, the radius of Venus is almost equal to that of the Earth (0.95), its mass is 0.82 that of the Earth. Venus has been studied quite well by people - both the Soviet Venus series spacecraft and the American Mariners approached the planet. Venus revolves around the Sun in 224.7 Earth days, but, unlike Mercury, nothing interesting is connected with this figure. Very interesting fact is associated with the period of rotation of the planet itself around its axis - 243 Earth days (in the opposite direction) and the period of rotation of the powerful Venusian atmosphere, which makes a complete revolution around the planet in... 4 days! This corresponds to a wind speed at the surface of Venus of 100 m/s or 360 km/h! It has an atmosphere first discovered by M.V. Lomonosov in 1761 during the passage of the planet across the disk of the sun. The planet is shrouded in a thick layer of white clouds, hiding its surface. The presence of thick clouds in the atmosphere of Venus, probably consisting of ice crystals, explains the planet's high reflectivity - 60% of incident sunlight is reflected from it. Modern scientists have established that the Venusian atmosphere consists of 96% carbon dioxide CO2. Nitrogen (almost 4%), oxygen, water vapor, noble gases, etc. (all less than 0.1%) are also present here. The basis of the thick cloud layer, located at an altitude of 50-70 km, is small drops of sulfuric acid with a concentration of 75-80% (the rest is water, actively “absorbed” by the acid droplets). There are active volcanoes on Venus, as it is reliably known that seismic and tectonic activity on Venus was very active relatively recently. The internal structure of this pseudo-twin of the Earth is also similar to the structure of our planet.
Earth
Our earth seems to us so large and solid and so important to us that we tend to forget the humble position it occupies in the family of planets of the solar system. True, the Earth still has a rather thick atmosphere covering a thin, heterogeneous layer of water, and even a titular satellite with a diameter of approximately ½ of its diameter. However, these special signs The earth can hardly serve as a sufficient basis for our cosmic “egocentrism.” But, being a small astronomical body, the Earth is the most familiar planet to us. Radius of the globe R=6378 km. The rotation of the globe most naturally explains the change of day and night, the rising and setting of the stars. Some Greek scientists also guessed about the annual movement of the Earth around the Sun. The annual motion of the Earth moves the observer and thereby causes a visible displacement of closer stars relative to more distant ones. Strictly speaking, the center of gravity of the Earth-Moon system, the so-called barycenter, moves around the Sun; The Earth and Moon describe their orbits around this center during the month.
Our ideas about internal structure And physical condition The subsoil of the globe is based on a variety of data, among which seismology data (the science of earthquakes and the laws of propagation of elastic waves in the globe) are of significant importance. The study of the propagation of elastic waves in the globe, arising during earthquakes or powerful explosions, made it possible to discover and study the layered structure of the earth's interior.
The air ocean surrounding the Earth - its atmosphere - is the arena in which various meteorological phenomena take place. The earth's atmosphere is mainly composed of nitrogen and oxygen.
The earth's atmosphere is conventionally divided into five layers: the troposphere, stratosphere, mesosphere, ionosphere and exosphere. The hydrosphere, or the World Ocean, whose surface is 2.5 times larger than the land area, has a great influence on many processes occurring on our planet. The globe has a magnetic field. Outside the dense layers of the atmosphere, it is surrounded by invisible clouds of very fast-moving high-energy particles. These are the so-called radiation belts. The structure and properties of the surface of our planet, its shells and interiors, magnetic field and radiation belts are studied by a complex of geophysical sciences.
Mars
When in 1965 American station Mariner 4 took pictures of Mars for the first time from a short distance, these photographs caused a sensation. Astronomers were ready to see anything but the lunar landscape. It was on Mars that those who wanted to find life in space had special hopes. But these aspirations did not come true - Mars turned out to be lifeless. According to modern data, the radius of Mars is almost half that of Earth (3390 km), and Mars is ten times less massive than Earth. This planet orbits the Sun in 687 Earth days (1.88 years). Solar days on Mars are almost equal to those on Earth - 24 hours 37 minutes, and the planet’s rotation axis is inclined to the orbital plane by 25), which allows us to conclude that the cycle is similar to the Earth’s (for Earth there are 23 seasons.
But all the dreams of scientists about the presence of life on the Red Planet melted away after the composition of the atmosphere of Mars was established. To begin with, it should be noted that the pressure at the surface of the planet is 160 times less than the pressure of the earth’s atmosphere. And it consists of 95% carbon dioxide, contains almost 3% nitrogen, more than 1.5% argon, about 1.3% oxygen, 0.1% water vapor, carbon monoxide is also present, traces of krypton and xenon have been found. Of course, no life can exist in such a rarefied and inhospitable atmosphere.
The average annual temperature on Mars is approximately -60; temperature changes during the day cause severe dust storms, during which thick clouds of sand and dust rise to heights of 20 km. The composition of the Martian soil was finally revealed during studies of the American Viking 1 and Viking 2 landers. The reddish luster of Mars is caused by the abundance of iron III oxide (ocher) in its surface rocks. The relief of Mars is very interesting. There are dark and light areas here, as on the Moon, but unlike the Moon, on Mars the change in surface color is not associated with a change in altitude: both light and dark areas can be at the same altitude.
Until now, scientists do not know the nature of the cataclysm that caused global climate change on Mars, leading to modern conditions.
