The Planets Planets in the night sky Five of the planets are visible with the naked eye at one time or another. They never stray very far from the circle around the sky called the ecliptic, the yearly path followed by the Sun against the constellations. Mars takes a retrograde step Mars' steady progress against the backdrop of stars is halted when the planet executes a zig-zag on its track. In reality it's the curious effect of Earth on its own orbit overtaking Mars on the inside. Venus and Mercury - going through the phases Lying between planet Earth and the Sun means that Mercury and Venus never stray far from the Sun in the sky, and both planets go through a cycle of Moon-like phases as viewed from our perspective. A double dawn on Mercury There are places on the surface of Mercury where you would witness the Sun come up then double back below the horizon before rising to stay up. Explore Mercury Explore the battered surface of a hot, desolate little world - the planet Mercury. Explore Venus Strip off the clouds of Venus and view the naked surface as revealed by Magellan's radar beam. Jupiter's Galilean moons Share the experience of Galileo Galilei in 1610 when he became the first person to turn a telescope on Jupiter. Follow the elaborate dance performed by the four moons Galileo discovered, exactly as he saw it. Strange seasons of Uranus Uranus' spin axis is tilted over so far, it seems to "lie on its side". As a consequence, Uranus experiences dramatic extremes of seasonal change. Neptune and its moons Neptune was the last planet visited by Voyager 2. Its moon Triton orbits the planet "backwards", and is now thought to be a close relative of the planet Pluto. Pluto and Charon A pair of diminutive icy worlds on the far-flung edge of the solar system reveal some of their secrets as they mutually eclipse. See also: The Essentials Sun, Moon and Earth Comets and asteroids Sights in the sky Spaceflight