The Solar System Introduction

 The Solar System Introduction

    The solar system is made up of the sun, nine planets, and many moons. All but two of the planets have at least one moon. Asteroids, meteoroids, and comets are part of the solar system, too. The sun is the center of our solar system. Earth orbits around the sun.
    There are nine planets: four inner planets and five outer planets. The inner planets orbit close to the sun. They are called the "rocky planets." They are made up mostly of rock. They have a few or no moons. The five outer planets orbit far from the sun. Most of them are made up of gases. All of the outer planets except one have many moons.
    Asteroids are a part of the solar system. They are made up of rock. Some people call them the "minor planets." Meteoroids are part of the solar system. They are smaller than asteroids, about the size of a pebble. The solar system includes comets. They are made up of gas, ice, and dust. They have long, thin orbits. They warm up as they go around the sun. Comets form heads and tails. Their tails are made of dust and ice. They look like falling stars in the sky.
    The United States sends spacecraft to explore the solar system. There is still much to learn about the sun, the planets, and other objects in our solar system.