The Sun is the star at the center of our solar system. It is composed of hot gas, providing abundant light and heat. The Earth orbits the moon. There are also eight planets in our solar system. The smallest is Mercury, and the largest is Jupiter. The planets rotate on their axis as they move around the Sun. One rotation of our planet is equal to a revolution of the Earth. This means that the earth would have to travel 450 years to travel the same distance as Usain Bolt.