Jupiter

Jupiter is the fifth planet from the Sun and by far the largest in the solar system. With a diameter of 139,820 km, Jupiter is more than 11 times wider than Earth and contains more mass than all the other planets combined -- 317.8 times the mass of Earth. This gas giant is composed primarily of hydrogen and helium, with no solid surface. If Jupiter had been about 80 times more massive, it would have had enough pressure and temperature at its core to ignite nuclear fusion and become a star. Jupiter's most iconic feature is the Great Red Spot, a massive anticyclonic storm that has been raging for at least 350 years. This storm is so large that Earth could fit inside it. The planet's rapid rotation (one day lasts less than 10 hours, the shortest in the solar system) creates powerful jet streams that produce the distinctive colored bands visible in its atmosphere. Deep within the planet, the intense pressure transforms hydrogen into an exotic liquid metallic state, which generates Jupiter's enormously powerful magnetic field -- the strongest of any planet, about 20,000 times stronger than Earth's. Jupiter has a vast system of at least 95 known moons, including the four large Galilean moons: Io (the most volcanically active body in the solar system), Europa (which harbors a subsurface ocean that may support life), Ganymede (the largest moon in the solar system, bigger than Mercury), and Callisto (one of the most heavily cratered objects known). Jupiter also has a faint ring system, discovered by Voyager 1 in 1979, composed mainly of dust particles from its inner moons.