Definition: The first of the outer planets, Jupiter is the largest planet in our solar system. One of the gas giants, it is the fifth planet from the sun. This massive planet is made up of gases, which form the appearance of stripes on its surface. The stripes are formed by the rapid rotation of the planet which causes different gases to separate and form bands of different colours. A red spot is clearly visible on the planet's surface, caused by a hurricane that has been raging on Jupiter for at least the last 400 years.