Patient observations reveal that the planets move against the background of stars as they orbit the sun. The closest planet to the Sun is Mercury, an airless ball of rock about the size of our Moon. Next is Venus, similar to Earth in size and distance from the Sun. It is covered with a thick layer of sulphur clouds, which have recently been penetrated by spacecraft which have sent back information about its surface. The next planet out from the Sun is Earth, whose oxygen-rich atmosphere and small temperature variations combine to support life.
Earth has one moon.
Mars is orbited by two moons, Phobos and Deimos. After Mars we find the asteroid belt, a huge ring of orbiting rocks. Many of the meteorites that we see burning up in our upper atmosphere as shooting stars come from here. Jupiter, the largest planet, lies beyond the asteroid belt. This gas giant could fit 1,000 Earths within it, but is still small compared to the sun, which has 1,000 times the volume of Jupiter.