Have you ever studied the night sky and wondered about all the things you can see? People have always been curious about the stars and planets in space. The Illustrated World of Space traces astronomy from the first space explorers, such as Galileo, to modern travelers like the space shuttle astronauts. The book also gives a lot of information about the nine planets and over 50 known moons in our solar system.

Did you know that the planets of the solar system are divided into two groups — the Inner Planets and the Outer Planets? Mercury, Venus, Earth, and Mars are the Inner Planets. Jupiter, Saturn, Uranus, Neptune, and Pluto are the Outer Planets. The Inner Planets are known as the Terrestrial planets. This is because they are small with solid surfaces. Four of the Outer Planets are called Giant or Jovian planets because they are large and made up of gases such as hydrogen. The Jovian planets do not have solid surfaces like Earth. The last of the Outer Planets, Pluto, is tiny and made up of ice.

The Inner Planets Venus and Mars are the two planets closest to Earth. Venus is closer to the Sun than Earth is, and the planet is very hot. It is hot enough to melt lead. A thick poisonous cloud layer covers all of Venus. Mars is farther from the Sun than Earth is. It is bitterly cold. Mars has a red rock-covered surface with many extinct volcanoes.

How much do you know about our own planet Earth and our moon? Earth is the third planet from the Sun. It orbits, or travels around, the Sun in a year (365.24 days). The Earth is the only planet in our solar system with liquid water on its surface. As far as we know, it's the only planet that has living plants and animals on it.

The Moon is Earth's nearest neighbor in space. The Moon has a pitted surface and is a barren, waterless place. It is just over a quarter of Earth's size, and it travels around the Earth in 27.3 days. The Moon always shows the same face turned toward Earth so that only spacecraft can see its far side.

Try The Ilustrated World of Space Activity to learn more about our solar system.