Jupiter is the fifth planet from the sun, and it is the largest planet in the solar system. It was named after the ruler of the gods in Roman mythology. Jupiter is one of the four gaseous planets. It takes about 11.9 earth years for Jupiter to orbit the sun, but a day on Jupiter is only 9.9 hours long. One of the most distinct features of Jupiter is the Great Red Spot. This spot is apparently a storm. Most of the atmosphere on Jupiter is hydrogen. About twice as much energy is radiated from Jupiter as it receives from the sun. Due to the fact that its polarity is opposite that of earth, a compass on Jupiter would point south. So far, sixteen satellites have been discovered around Jupiter. The four largest are: Io, Europa, Ganymede, and Callisto. The moon Ganymede is bigger than Mercury! Very close to the planet, a faint system of rings can be detected.