Our solar system is made of nine planets. The sun uses its gravity to keep the planets circling around it.
The Sun is much bigger than Earth. Did you know that 1.3 million Earths can fit inside of the Sun? If the Sun was a beach ball, the Earth would be the size of a tiny pea and the moon would be the size of a pinhead.
The four planets closest to the sun are balls of rock. They are Mercury, Venus, Earth, and Mars. The other planets are gas and liquid. Those are Jupiter, Saturn, Uranus, and Neptune. Pluto used to be a planet. Scientists decided that it would be best to exclude it from the solar system due to its size. Some planets have moons that circle around them. Earth only has one moon; Pluto also has one moon. Mars has two tiny moons. And Mercury and Venus have no moons
There are still many planets out there to discover in other solar systems.
[Source: 100 Things You Should Know About Space]