The solar system that we live in is probably only one of many others in the universe. Our Solar System has a total of nine planets, but some scientists think that there are more. All of the planets revolve around the Sun at the center of the Solar System.

There are two sets of planets: the inner and the outer planets. The Inner Planets include Mercury, Venus, Earth, and Mars, and the Outer Planets include Jupiter, Saturn, Uranus, Neptune, and Pluto. All of the Inner Planets are made mostly of iron, rock, and dust. That is why they are also known as the Terrestrial Planets. The Outer Planets on the other hand are made mostly of gas (e.g. hydrogen, helium, methane, etc.) and have little or no iron, rock, or dust. All of the Outer Planets are made of this except Pluto which seems more terrestrial than the other Outer Planets.

The Inner and Outer Planets are separated between Mars and Jupiter by a large asteroid field called the Asteroid Belt. Scientists think that they are the leftover remains of what made the planets. If you want to know more about the Solar System, continue reading the lessons and we will go into each part of the Solar System more in depth.

These are the nine planets in the Solar System.
(Courtesy to Microsoft Encarta for this photograph)

Click here to continue on to the next lesson (the Sun).
Click here for a printable version of this page.