Solar System

What is the solar system? It is our Sun and everything that travels around it. The Sun is in the center of the solar system. Our solar system is always in motion. Eight known planets, along with comets, asteroids, and other space objects orbit the Sun. The Sun is the biggest object in our solar system. It contains more than 99% of the solar system's mass. Nearest the Sun are four fairly small, rocky planets - Mercury, Venus, Earth and Mars. 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 furthest 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.