The Solar System

Introduction

Our solar system is made up the sun, eight planets, more than 150 moons, as well as comets, asteroids, dwarf planets and other space rocks.

Planets, asteroids and comets orbit the sun. They travel around our sun in an ellipse. It takes Mercury, the nearest planet, only 88 days but Neptune 164 years to travel around the sun once.

Moons orbit planets. Currently, Jupiter has the most moons - over 60. Mercury and Venus don't have any moons.

The inner planets Mercury, Venus, the Earth and Mars are called terrestrial planets. This means they have a hard surface to stand on. Jupiter, Saturn, Neptune and Uranus are the outer planets. They are also called the gas giants because you can't stand on them - their surface is made of gas.

There are many theories on how the solar system developed. About 4.5 billion years ago a big cloud of gas and dust probably collapsed. The sun formed in the middle, the densest region. Further away from the sun, gases changed to planets made of rock.

The planets of our solar system
Image : International Astronomical Union/NASA, edited by w:User:SG.,
Public domain, via Wikimedia Commons