The eight described planets all orbit the Sun at different distances; Mercury is the closest planet to the sun, followed by Venus, then Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The distances of the planets are normally measured in kilometers, because scientists use metric measurements. However, scientists also use a unit called an “astronomical unit,” which is equal to the distance between Earth and the sun.
Mercury is a hot, barren world that orbits the Sun at a distance of roughly 57 million kilometers. However, due to its heavy cloud cover and runaway greenhouse effect, Venus is hotter, even though it orbits the Sun at a distance of 108 million kilometers. The Earth is about 150 million kilometers from the Sun, which means that 1 AU is equal to about 150 million kilometers. Mars, the second closest planet to Earth, is about 228 million kilometers from the Sun.
Jupiter, Saturn, Uranus and Neptune are often called the outer planets, and they are very far from the sun. Only their large size makes them visible from the Earth from such long distances. Jupiter is about 778 million kilometers from the Sun, while Saturn is almost 1.5 billion kilometers from the Sun. Uranus and Neptune are even farther, orbiting the sun from a distance of 2.8 billion and 4.5 billion kilometers, respectively.