The
Solar System and its planets
The Solar System is made up of the Sun and the smaller objects that move
around it. Apart from the Sun, the largest members of the Solar System are the
eight major planets. Nearest the Sun are four fairly small, rocky planets -
Mercury, Venus, Earth and Mars.
Beyond Mars is the asteroid belt – a region populated by millions of rocky
objects. These are left-overs from the formation of the planets, 4.5 billion
years ago.
On the far side of the asteroid belt are the four gas giants - Jupiter, Saturn,
Uranus and Neptune. These planets are much bigger than Earth, but very
lightweight for their size. They are mostly made of hydrogen and helium.
Until recently, the farthest known planet was an icy world called Pluto.
However, Pluto is dwarfed by Earth’s Moon and many astronomers think it is too
small to be called a true planet.
An object named Eris, which is as big as Pluto, was discovered far from the Sun
in 2005. More than 1,000 icy worlds such as Eris were discovered beyond Pluto in
recent years. These are called Kuiper Belt Objects.
- ESA |