Image solar system

The Solar System: a general description

The Solar System is made up of the Sun and all the objects that revolve around it, the eight known planets together with their moons, comets, asteroids and other celestial bodies.

The Sun and the eight planets are drawn in sequence: their shape is practically spherical, therefore in this drawing as in the following ones the circles drawn represent the spherical shape of these bodies.

On the far left, only a part of the Sun is shown as it is too big to be drawn in full in this specific illustration. Moving towards the right, the planets closest to the Sun, also known as inner planets, have been drawn in order: Mercury, a tiny dot to the immediate right of the Sun, Venus and Earth, whose dimensions are almost the same, and then Mars. Then, there are the planets that are furthest away from the Sun, known also as the outer planets: Jupiter, Saturn with its system of rings around it, then Uranus and Neptune, which are both almost the same size.

In the drawing the size of the Sun and the planets is represented proportionally. The distance between them, however, is by no means realistic because it would be impossible to represent both the size of the planets and the distance between them on a single page. In actual fact, the planets are so far from each other that the Solar System is more or less empty. If we take the distance between the Sun and the Earth to be equal to 1 then the following show the distances between the eight planets and the Sun:

Mercury 0,3 Venus 0,7 Earth 1 Mars 1,5 Jupiter 5,2

Saturn 9,5 Uranus 20 Neptune 30

From the drawingit is very clear that the Sun is the biggest object in our Solar System, just think that it contains over 99% of the mass of the entire System.

Another interesting fact to note, is that the inner planets are much smaller than the outer ones, which are called the "giant planets". The inner planets are solid and rocky spheres, while the outer ones are gassy spheres that do not have a true solid surface.

Astronomers believe that the Solar System was formed almost 5 billion years ago from the condensation of an immense cloud of whirling gas and dust. The beginning evolutive phase of our Solar System was very violent, it was characterized by numerous impacts between the various bodies that were being formed.

We can imagine a solar system with an extremely high density of small bodies such as asteroids which continuously collide into each other or into bigger bodies such as planets or big satellites, such as the Moon. Indeed the hundreds and hundreds of craters on the surface of the Moon bear testimony to this violent age.

Then, about 4 billion years ago, it reached a period of relative tranquillity and equilibrium, and this is still our present situation.

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