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A Very Brief Overview of the Solar System.
We all know that we live on a planet called Earth. But what is a planet? It is a round celestial body of considerable size that revolves around a star. Our star, around which our home planet revolves, is the Sun—one of billions upon billions of stars that we see in the night sky. All the other stars are simply very, very far away from us, which is why they appear as points of light. Even through powerful telescopes, they still appear to us as points—that is how distant they are!
Our star—the Sun—is much closer to us, so it appears to us to be the size of a disk, but it is enormous. It is a huge ball of fire, literally burning like a bonfire. It shines on us and warms us. Thanks to the Sun, everything grows on Earth. And various creatures live here (not all of them are visible to us). Without the Sun, there would be no life here at all.
And all stars are such balls of fire, with planets revolving around them as well. Eight planets revolve around our Sun.
The proportions of sizes and distances in the illustration are not to scale.
The closest to the Sun and the smallest is Mercury. It has almost no atmosphere; there is no “air” on it. Therefore, when one side faces the Sun, it heats up to +420 degrees, while the side facing away from the Sun cools down to −170 degrees. Earth is surrounded by an atmosphere, a layer of air that we breathe, and our atmosphere protects us from major temperature fluctuations. Mercury has no satellites (such as our Moon).
The second planet from the Sun, Venus, is surrounded by a thick, dense layer of poisonous gases, which makes it even hotter there than on Mercury. Venus is smaller than Earth. Venus also has no satellites.
The third planet is our Earth, and the fourth is the red Mars. It is smaller than Venus. It appears red in the sky because it has reddish-brown sands, and powerful sandstorms often occur there. Mars is clearly visible without a telescope. Mars has two satellites—Phobos (“fear” in Greek) and Deimos (“terror”).

The first four planets are relatively small; they are called terrestrial, or inner, planets. They have solid surfaces consisting of soil, mountains, rocks, and solid rock formations.

A comparison of the sizes of the four inner planets.
The fifth planet from the Sun is Jupiter, the largest planet in our solar system and a gas giant. Jupiter has 79 satellites; the largest, Ganymede, is bigger than Mercury.
The sixth planet is Saturn, surrounded by its famous rings. The rings are clearly visible through a telescope and even through binoculars; they are very beautiful. Saturn is also a huge gas giant, slightly smaller than Jupiter. Saturn has 82 satellites; the largest is Titan.
The seventh and eighth planets, Uranus and Neptune, are also gas giants, smaller than Jupiter and Saturn. They are not visible to the naked eye, only through a telescope. Uranus has 27 satellites, and Neptune has 13. Astronomers are constantly discovering new satellites around all the gas giants. All these giant planets also have rings, but not as substantial as Saturn’s. The rings consist of dust, ice, and rocks.
Jupiter, Saturn, Uranus, and Neptune are called outer planets or giant planets, because they are much larger than the terrestrial planets. They consist mainly of gases.

By size: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury.

The four outer giant planets compared with the Sun, from left to right: Jupiter, Saturn, Uranus, and Neptune.
Besides the planets, many other celestial bodies orbit the Sun—dwarf planets, asteroids—shapeless fragments possibly left over from a planet that broke apart in ancient times—and comets—icy bodies that acquire a “tail” as they approach the Sun. That is, some of the comet’s material breaks away from it (under the influence of the Sun’s radiation) and stretches across enormous distances in the form of several tails. Moreover, a comet’s tail always points away from the Sun, so when a comet is moving away from the Sun, its tails are positioned in front of it: the tails come first, followed by the comet itself.

Hale–Bopp comet, 1997. It was clearly visible to the naked eye for many months, including in Yerevan.

The green ATLAS comet, 2019.
We all know that we live on a planet called Earth. But what is a planet? It is a round celestial body of considerable size that revolves around a star. Our star, around which our home planet revolves, is the Sun—one of billions upon billions of stars that we see in the night sky. All the other stars are simply very, very far away from us, which is why they appear as points of light. Even through powerful telescopes, they still appear to us as points—that is how distant they are!
Our star—the Sun—is much closer to us, so it appears to us to be the size of a disk, but it is enormous. It is a huge ball of fire, literally burning like a bonfire. It shines on us and warms us. Thanks to the Sun, everything grows on Earth. And various creatures live here (not all of them are visible to us). Without the Sun, there would be no life here at all.
And all stars are such balls of fire, with planets revolving around them as well. Eight planets revolve around our Sun.
The proportions of sizes and distances in the illustration are not to scale.
The closest to the Sun and the smallest is Mercury. It has almost no atmosphere; there is no “air” on it. Therefore, when one side faces the Sun, it heats up to +420 degrees, while the side facing away from the Sun cools down to −170 degrees. Earth is surrounded by an atmosphere, a layer of air that we breathe, and our atmosphere protects us from major temperature fluctuations. Mercury has no satellites (such as our Moon).
The second planet from the Sun, Venus, is surrounded by a thick, dense layer of poisonous gases, which makes it even hotter there than on Mercury. Venus is smaller than Earth. Venus also has no satellites.
The third planet is our Earth, and the fourth is the red Mars. It is smaller than Venus. It appears red in the sky because it has reddish-brown sands, and powerful sandstorms often occur there. Mars is clearly visible without a telescope. Mars has two satellites—Phobos (“fear” in Greek) and Deimos (“terror”).

The first four planets are relatively small; they are called terrestrial, or inner, planets. They have solid surfaces consisting of soil, mountains, rocks, and solid rock formations.

A comparison of the sizes of the four inner planets.
The fifth planet from the Sun is Jupiter, the largest planet in our solar system and a gas giant. Jupiter has 79 satellites; the largest, Ganymede, is bigger than Mercury.
The sixth planet is Saturn, surrounded by its famous rings. The rings are clearly visible through a telescope and even through binoculars; they are very beautiful. Saturn is also a huge gas giant, slightly smaller than Jupiter. Saturn has 82 satellites; the largest is Titan.
The seventh and eighth planets, Uranus and Neptune, are also gas giants, smaller than Jupiter and Saturn. They are not visible to the naked eye, only through a telescope. Uranus has 27 satellites, and Neptune has 13. Astronomers are constantly discovering new satellites around all the gas giants. All these giant planets also have rings, but not as substantial as Saturn’s. The rings consist of dust, ice, and rocks.
Jupiter, Saturn, Uranus, and Neptune are called outer planets or giant planets, because they are much larger than the terrestrial planets. They consist mainly of gases.

By size: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury.

The four outer giant planets compared with the Sun, from left to right: Jupiter, Saturn, Uranus, and Neptune.
Besides the planets, many other celestial bodies orbit the Sun—dwarf planets, asteroids—shapeless fragments possibly left over from a planet that broke apart in ancient times—and comets—icy bodies that acquire a “tail” as they approach the Sun. That is, some of the comet’s material breaks away from it (under the influence of the Sun’s radiation) and stretches across enormous distances in the form of several tails. Moreover, a comet’s tail always points away from the Sun, so when a comet is moving away from the Sun, its tails are positioned in front of it: the tails come first, followed by the comet itself.

Hale–Bopp comet, 1997. It was clearly visible to the naked eye for many months, including in Yerevan.

The green ATLAS comet, 2019.
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