The first 4 planets, starting closest to the Sun, are Mercury, Venus, Earth and Mars. These are the "terrestrial" planets (so called because they are close to the Earth "Terra" in Latin). These inner, small, rocky planets were formed from small particles of rock and dust left over after the Sun ignited. Over time they stuck together to form larger and larger rocks then boulders and eventually planets.

You can click the planet name links on the left or any of the planets below to learn more.

The second 4 planets are the outer gas giant planets, Jupiter, Saturn, Uranus and Neptune. These were formed from gases (mostly hydrogen and helium) that are lighter than rock and dust and were thrown further out away from the Sun when it ignited.

You can click the planet name links on the left or any of the planets below to learn more.