It is also the smallest planet in the solar system. Pluto is made up of rocky materials and frozen gases. Little is known about Pluto because it is so far away. Asteroids and comets are also part of the solar system. An asteroid is a small chunk of rock or metal that orbits the Sun.
Asteroids come in a variety of shapes and sizes.
Most asteroids are found between Mars and Jupiter. This part of space is called the asteroid belt. A comet is a body of ice and rock that moves around the Sun in long, narrow orbits. When a comet passes close to the Sun, it becomes very warm. Some of the ice changes to gases.