What is the Solar system?

The solar system is the Central star, the Sun and all the planetary bodies that revolve around it.

The structure of the Solar system

In the solar system 8 the largest of the heavenly bodies, or planets. Our Earth is also a planet. Besides her, around the Sun make its journey in space 7 planets: mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune. The last two from the Earth can be observed only through a telescope. Remaining visible to the naked eye.

More recently, the number of planets counted another celestial body – Pluto. It is very far from the Sun, beyond the orbit of Neptune, was discovered only in 1930. In 2006, however, astronomers have introduced a new definition of a classical planet, and Pluto has not got.

The comparative sizes of the Sun and planets of the Solar system

The planet is known to people since ancient times. Closest neighbors of the Earth – Venus and Mars, the most distant from it – Uranus and Neptune.

Large planets can be divided into two groups. The first group includes the planets that are closest to the Sun are planets of terrestrial group . or the inner planets . – Mercury, Venus, Earth and Mars. All these planets have high density and a hard surface (although underneath it is liquid core). The largest in this group the planet Earth. However, far from the Sun the planets – Jupiter, Saturn,Uranus and Neptune greatly exceed the Earth in size. Therefore, they are called giant planets . They are also called outer planets . Thus, the mass of Jupiter exceeds the mass of the Earth more than 300 times. Giant planets are significantly different from the terrestrial planets in their structure: they do not consist of heavy elements and gas, mainly of hydrogen and helium, like the Sun and the other stars. The giant planets have no solid surfaces – just gas balls. So they are called gas planets .

Between Mars and Jupiter is the asteroid belt . or small planets . An asteroid is a small body planetology of the Solar system, ranging in size from a few meters to thousands of kilometers. The largest asteroid belt – Ceres, Pallas and Juno.

Beyond the orbit of Neptune is another belt of small celestial bodies called the Kuiper belt. It is 20 times wider than the asteroid belt. Pluto, which lost its status as a planet was classified as dwarf planets . it is in this zone. In the Kuiper belt there are other dwarf planets similar to Pluto, in 2008 was named plutoid . This Makemake and Haumea. By the way, Ceres from the asteroid belt also belong to the class of dwarf planets (but not plutoids!).

Another plutoid – Eris – is comparable in size with Pluto, but is much farther from the Sun beyond the Kuiper belt. It is interesting that Eris at one time was candidate for the 10th planet in the Solar system. But the result was the discovery of Eris caused the revision of the status of Pluto in 2006 when the international astronomical Union (IAU) established a new classification of celestial bodies in the Solar system. According to this classification, Eris and Pluto do not fall under the concept of a classical planet, and “deserve” only the title of the dwarf planets – celestial bodies that revolve around the Sun, are satellites of the planets and have a sufficiently large mass to maintain a nearly round shape, but, unlike planets, are not able to clear its orbit from other objects in outer space.

In the composition of the Solar system, beyond the planets are the satellites that revolve around them. All satellites now totals 415. Constant companion of Earth – the Moon. Mars has 2 satellites – Phobos and Deimos. Jupiter has 67 satellites, and Saturn has 62. 27 moons has Uranus. And only mercury and Venus have no satellites. But the “dwarfs” of Pluto and Eris have satellites: Pluto is Charon, and Eris – Dysnomia. However, astronomers have not yet come to a final conclusion whether Charon is a satellite of Pluto or the system Pluto-Charon is a double planet. Even some asteroids have satellites. Champion in size among the satellites – Ganymede, moon of Jupiter, slightly behind Saturn’s moon Titan. And Ganymede and Titan exceed the size of mercury.

In addition to planets and satellites, Solar system travel through tens or even hundreds of thousands of different small bodies . tailed celestial body – a comet, a huge amount of meteorites, particles of gas-dust matter, dispersed atoms of different chemical elements, fluxes of atomic particles and others.

All objects in the Solar system are kept in it due to the gravitational forces of the Sun, and they all revolve around him, and in the same direction with the rotation of the Sun itself and almost in the same plane, called the Ecliptic plane . With the exception of some comets, and objects in the Kuiper belt. In addition, almost all objects in the Solar system rotate around its axis, and in the same direction as that around the Sun (with the exception of Venus and Uranus; the latter does rotates “lying on its side”).

Planets of the Solar system revolve around the Sun in the same plane – the Ecliptic plane

The Ecliptic plane of the Solar system

Pluto’s orbit is highly inclined relative to the Ecliptic (17°) and elongated

In the Sun is concentrated almost all the mass of the Solar system is 99.8%. Four of the largest object — the gas giants comprise 99% of the rest mass (the bulk — about 90 percent — are in Jupiter and Saturn). As for the size of the Solar system, astronomers have not yet come to a consensus on this issue. According to current estimates, the size of the Solar system is at least 60 billion kilometers. To at least roughly imagine the scale of the Solar system, provide a more clear example. Within the Solar system per unit distance take astronomical unit (a. E.) – the average distance from the earth to the Sun. It is approximately 150 million km (light travels this distance in 8 minutes 19). The outer boundary of the Kuiper belt is at a distance of 55 and. that is from the Sun.

Another way to imagine the real size of the Solar system is to imagine a model in which all dimensions and distances reduced by a billion times . In this case, the Earth would be about 1.3 cm in diameter (about the size of a grape). The moon will rotate a distance of about 30 cm from it. The sun would be 1.5 meters in diameter (about the height of a man) and located at a distance of 150 meters from the Ground (about a city block). Jupiter is 15 cm in diameter (the size of a large grapefruit) and at a distance of 5 city blocks from the Sun. Saturn (the size of an orange) is 10 blocks away. Uranus and Neptune (lemons) 20 and 30 blocks. People on this scale would be the size of an atom; the nearest star is at a distance of 40 000 km.

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