Solar system planets Artwork showing the Sun left and the eight planets of the solar system and their orbits From left to right they are Mercury Venus Earth Mars Jupiter Saturn Uranus and Neptune The inner planets are mostly rock and metals while the outer gas giant planets are mostly hydrogen and helium Jupiter is the largest planet and Mercury the smallest Both Saturn and Uranus have ring systems The nuclear fusion of hydrogen in the Suns core produces the sunlight and energy that sustains life on Earth The Milky Way is at top right This artwork is not to scale
