Jupiter is composed primarily of hydrogen and helium, has a diameter of 88,700 miles, and has a day that is approximately 9.92 hours. It is the fifth planet from the sun and has 63 known moons, with its years equivalent to approximately 84 Earth years due to its greater distance from the sun. Jupiter was named after the Roman king of the gods and is characterized as having faint rings and never having been landed on by spacecraft.