His name is appropriate for our largest planet. A traditional sign for his lightning bolt gives the planet its symbol.
Jupiter (Iuppiter, Juppiter, and/or Jove) was the ancient Italian Father or Lord of Heaven and provider of fertilizing rains giving him another name: Jupiter Pluvius. He gave day and night to mankind, sent the snow and the rain, and caused the winds to blow and the dark storm clouds to gather. The lightning with the crash of thunder that followed was but an expression of his anger. He was the supreme god of the Romans who gradually became identified with the Greek god Zeus. Jupiter was thought to be the lord of life, light, and aerial phenomena. Although, like Zeus, he was lord of life and death, unlike Zeus he was not controlled by the Fates or Moirae. He still determined the course of human affairs and foretold the future through the flight of birds and other signs in the heavens. Jupiter was the brother and husband of Juno, whose Greek equivalent is Hera.
Jupiter is the greatest of the planets; it is the largest body in the solar system except the Sun. His planet is the fifth in order from the Sun and the brightest. It is considered to be the royal planet and ruler of the zodiacal mansion Sagittarius. We get jovial from the word Jove, one of the forms of the name Jupiter, which means born under the lucky planet, Jupiter, and therefore happy and healthy. Thursday came to us in its present form from Old English meaning Thors Day, and was adapted from the Late Latin of Jupiters Day because Thor and Jupiter represent very similar powers. Since Jove is another form of Jupiter, it is easy to see how the French jeudi, the Italian giovedi, and the Spanish jueves have continued to preserve the term Jupiters Day for the fifth day of the week.
Master of its orbit, Jupiter holds a faint ring system and at least sixty-three moons in its gravitational grip. Four moons are as big as small planets. The combined pulls of Jupiter and the Sun also keep two asteroid groups, called the Trojans, in Jupiters orbit. One group moves along a sixth of the way ahead of Jupiter, the other equally far behind. They bear heroes names from the ancient Trojan War; the first group represents Greece, the second Troy. Jupiters tiny outer moons may be Trojan asteroids, trapped when they strayed too close to the planet. The evidence comes from photos of the Valles Marineris taken by the Viking 1 orbiter (launched in 1975 and reaching Mars on July 20, 1976). As heavyweight champion of the worlds, Jupiter accounts for more than two-thirds of all material in the Solar System outside the Sun. It would take 318 Earths to equal Jupiters huge mass. Gravity two and a half times stronger than our own creates intense pressures in the swirling gases of its atmosphere. Scientists think electrical currents on Jupiter may create its giant magnetic field, which extends past the orbits of several of its moons. Jupiters four largest moons: Io, Europa, Ganymede, and Callisto were discovered by Galileo on January 7, 1610. Some astronomers refused to believe Galileos claim because they felt that the Solar System with its seven planets was complete and they were very upset that an age-old belief could be wrong. As stated previously in the list under planets, the ancients thought that the seven planets (Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn) were complete and that there were no other planets (or moons). Eventually, even Galileos bitterest enemies had to admit that Jupiter had moons. Measuring 5,276 kilometers in diameter, Ganymede is Jupiters and the Solar Systems biggest moon.