Journey through the Solar System

Bound to the immense mass of the Sun by gravity, the contents of our solar system are numerous and spectacular.
The solar system formed about 4.6 billion years ago, when part of a giant molecular cloud had a gravitational collapse. The centre became the Sun, which comprises more than 99 per cent of the solar system's total mass. The rest became a dense, flat rotating disk of gas from which planets formed, called a protoplanetary disk. In our solar system, most of that disk became the eight planets, each of which orbits the Sun.

There are two different categories of planets: gas giants and terrestrials. The gas giants are the four outer planets: Jupiter, Saturn, Uranus and Neptune. They are much bigger than the terrestrial planets and are mostly made of helium and hydrogen, although Uranus and Neptune also contain ice. All of the outer planets have ring systems made of cosmic dust. These planets comprise more than 90 per cent of the rest of the solar systems mass.
The four inner planets are very close to the Sun. To grant perspective, for example, the distance between Jupiter and Saturn is larger than the radius of all the inner planets together. These terrestrials are made up from rocks and metals, have no ring systems and have a low number of moons. they include Mercury, Venus, Earth and Mars. Except for Mercury, the inner planets also have recognisable weather systems operating in their atmospheres. 
In addition to the eight main planets, there are also dwarf planets such as Pluto. The five dwarf planets are Ceres, Pluto, Haumea, Makemake and Eris. In addition, the solar system is home to numerous small solar system bodies, which include all minor planets, asteroids and comets.