The solar system is formed by an enormous quantity of celestial bodies. Apart from the 8 planets that orbit around the Sun, there is also a big quantity of celestial bodies which are grouped together in big systems. We distinguish 3 different asteroid systems: the Oort cloud, the Kuiper belt and the asteroid belt. This last one is the closest of them to the Earth.
The asteroid belt is situated between Mars’ and Jupiter’s orbits. Even if we don’t know exactly how the asteroid belt was formed, different hypothesis exist about its origin and formation, 4,5 thousands of milions of years ago.
There are many hypothesis about he formation of the asteroid belt, which is formed of about 960 000 asteroids, between which some of them have their own satellites. About 18 000 asteroids have got a name, and about 95 000 are identified using numbers. Two main hypothesis exist about the formation of the asteroid belt.
Some scientists think that the formation of the asteroid belt was due to the destruction, caused by gravitational forces of Jupiter, of a planet that was formed between the orbits of Mars and Jupiter. As a result, the remainders were scattered around the orbit of what nowadays we know as the asteroid belt.
The other theory suggests that, also due to the gravitational forces of Jupiter, it was a planet that didn’t manage to completely form. According to this theory, any planet was formed. What it had to happen was that one planet had to form, but the gravitational forces of Jupiter prevented it to form.
At the beginning, the solar system was a primitive nebula that was mainly composed by gas and dust. The nebula collapsed and it gradually formed a disc which started turn. In the furthest zones from the centre (in this centre is where the Sun was formed), some small grains made of rocks and dust formed, which after some time grouped together until the point of forming planets. Many of these rock groups weren’t able to group together, thing which provoked them to convert into isolated asteroids.
In the past, where the asteroid belt is nowadays, there were much more asteroids, but the great part of them were ejected to the outsides of the solar system, mainly to what nowadays we know as the Oort cloud. It is thought that in our days there only remains a 0,1% of the asteroids, among all of which there had been in the past.