What is space?

By admaskr May2,2024
What is space?


So what is space? The word “cosmos” is translated from Greek as “order”, “structure”. Cosmos, or the Universe, as they call it, is the whole world, everything that surrounds us. Ever since the first rocket launched from Earth, people began to call space what is outside the atmosphere (a dense layer of air more than 500 km thick) of our planet.

Space, or outer space, is a void. There is no air, so we cannot breathe in outer space. In this void there are black holes, comets, stars, planets and their satellites. There is still a lot of cosmic dust in space. This is a huge number of small particles. Depending on where it is, there is interstellar, cometary, and other dust.


A star is a huge ball of heated gases, inside which a reaction is constantly taking place, as in a nuclear power plant. When burned, these gases give off a lot of heat and light. This is why stars are hot and shine brightly. Stars do not shine forever. They are born in groups from huge gas and dust clouds, which are also called nebulae. Stars mature for a long time, grow old, gradually cool down, having used up their fuel.



A galaxy is a cluster of star systems held together by gravity. There are more than a billion galaxies in the universe, they are separated from each other by huge distances. Galaxies have different shapes and sizes. The shape of galaxies can be epileptic, spiral, and irregular (without a clear shape).

Planet Earth is located in the Milky Way galaxy. If you look at the sky at night, you can see a band of stars. This is the Milky Way galaxy. At its very edge lies the Solar System, which includes the planet Earth. The shape of our galaxy resembles a plate. But if you look at it from above, it will look like a huge spiral. In total, there are 150-200 billion stars in the Milky Way galaxy.

Star system

A stellar system is a system consisting of a star or group of stars, and possibly planetary systems of smaller bodies (such as planets or asteroids) held together by gravity. Each star in the star galaxy has a force of attraction – gravity. This force is so huge that it attracts cosmic objects with a smaller mass to the star. That is why the planets do not fly apart in space, but revolve around their stars, each in its own orbit (an orbit is the path along which the planets fly around their star, and the satellites around the planets). Planets also attract smaller cosmic bodies. This is how it turns out that the star system consists of stars, their planets and their satellites.

Solar system

The solar system is a planetary system that includes the central star, the Sun, and smaller objects that revolve around it — the planets and their satellites, dwarf planets, asteroids, comets, meteorite matter, etc. It was formed by the gravitational compression of a gas-dust cloud about 4.567 billion years ago. The solar system is part of the Milky Way galaxy.

Like all stars, the Sun is a huge ball of hot gas. According to scientists, it is approximately 4.5 billion years old, and during this time it has consumed half of its water fuel. Therefore, it will shine for the same amount of time, and then it will gradually cool down. It was established that the color of a star depends on its temperature: the hottest stars are white and blue, the coldest are dull red. The sun is a yellow star. This means that it has an average temperature for a star. On the surface of the Sun, the temperature is approximately 6000 C – enough to melt any object that gets there. And inside it is much hotter (the temperature of the core reaches 15,000,000 C).

Planets of the solar system

There are eight planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Five of them – Mercury, Venus, Mars, Jupiter and Saturn – we can see with the naked eye, without the help of a telescope. The planets not only rotate around their axis (an imaginary line passing through the center of the planet), they also travel around the Sun, each in its own orbit, without stopping for a minute. The orbits of the planets have the shape of a flattened circle.

Planets formed from the same cosmic dust and gas as stars, but they are much smaller than stars and not as hot. They do not emit light themselves, but only reflect the light of the stars that falls on them. That is why we see them.

All the planets of the solar system are different, although they formed at about the same time. They move around the Sun and around their axis counterclockwise. Only Venus rotates in the opposite direction. The four planets closest to the Sun – Mercury, Venus, Earth and Mars – are called the inner planets. They consist mainly of rocks and metals, so this group of planets is also called terrestrial. There are three outer planets: Jupiter, Saturn, Uranus. They consist of gases and have a huge size.

The time of rotation around the Sun and around its axis is different for all planets.

The largest and smallest planet of the solar system


The largest planet in the Solar System is the gas giant Jupiter. It weighs twice as much as the rest of the seven planets combined, and is about eleven times the size of Earth. Stormy winds are constantly blowing on Jupiter. This can be seen from the beautiful marble pattern that is formed by the gas clouds.

The smallest and at the same time the closest planet to the Sun is Mercury, it is only slightly larger than the Moon.

Venus is the hottest. The gaseous atmosphere of Venus is very dense, and the layer of clouds 60 km thick, with which it is always covered, well preserves the heat received from the Sun.


The coldest is Uranus. Uranus, like Neptune, has a lot of ice in its interior, so scientists have separated these two planets into a separate category of “ice giants.” Uranus has the coldest atmosphere in the Solar System with a temperature of -224 C.

On the surface of Mars, there is a lot of dust with a high iron content, which oxidizes (rusts). That is why the planet appears red. There is no water on Mars. Mars is more like Earth than other planets. His day lasts 24 h 37 min. Mars even has seasons.

Saturn is one of the most beautiful planets in the solar system. It is distinguished by huge bright rings. They are made up of the tiniest particles of ice and dust, each of which orbits Saturn as an individual tiny moon. The width of the rings reaches 400,000 km, and the thickness does not exceed a kilometer. Saturn has more satellites than any other planet. The largest of them is Titan.

Mercury, Venus, Mars, Jupiter, Saturn are named after the Roman gods, and the planet Uranus is named after the Greek sky deity.

Our ancestors called the soil they walked on earth. When it became known that we live on the planet, it also began to be called the word “earth”, only it should be written with a capital letter.

Moons of the solar system

Satellites of planets are called moons. They do not revolve around a star, but around their planet. The Earth has only one moon, it is called the Moon. Mercury has no moons at all, and Saturn already has 60 of them. The surface of the moons is usually covered with large and small craters – traces of collisions with huge meteorites.

The largest moon in the solar system is Ganymede, a satellite of Jupiter. It is almost twice the size of our Moon. And the smallest moon, the dimensions of which are not exactly known, is Deimos, a satellite of Mars. Its diameter is less than 10 km.

Does the moon change shape? No, it is always round. The fact is that the moon does not emit light like the stars, but shines with the reflected light of the Sun. Depending on the position of the Moon relative to the Earth, the illuminated part of its surface that we see in the sky changes. These parts are called phases.


A comet is a small body of the Solar System that, passing near the Sun, heats up and begins to emit gases. A comet has an icy core. It usually consists of frozen gas, dust and small rocks. Comets orbit the Sun and begin to glow when they get close enough for the ice to heat up, melt, and vaporize. Then a glowing gas tail appears in the comet.


Meteorites are solid bodies of cosmic origin that fell to the Earth's surface. Most meteorites weigh from a few grams to several kilograms.

Black hole

A black hole is a cosmic object that creates such a strong gravitational force that nothing, not even light, can leave it. Its gravity becomes so strong that the black hole, like a vacuum cleaner, sucks everything nearby. A black hole absorbs light rays, so it cannot be seen even in the most powerful telescope. However, a black hole can be detected when it begins to suck in a star that has appeared in its path: after all, a stream of glowing gas can be seen in a telescope.

Starry sky

The starry sky is not just a lot of bright spots on a dark background. The entire sky is divided into sections – constellations. Their names and forms seem strange and mysterious to us. And you can tell an interesting story about almost every one of them.

Even thousands of years ago, people combined clusters of stars in the sky into conventional figures – constellations. the earth is constantly moving, and therefore the location of the constellations in the sky also changes – depending on the season and time of day. In order to better remember the location of the stars and to navigate more easily with their help in space, people created maps of the starry sky. But different stars are visible in the Northern and Southern hemispheres, so a map was made for each hemisphere.

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