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Jupiter General Information & History

Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. The Jovian system is made up of Jupiter and the many moons orbiting it. To date, 67 of these satellites have been discovered.


Planet Jupiter

Jupiter is one of five planets that can be seen by the naked eye (Mercury, Venus, Mars and Saturn are the other four); in fact, it is the second brightest planet after Venus. In terms of visibility, Jupiter is a night planet. It is best seen from dusk until the early morning. Its location however varies with the time of year, day and time. The best way to locate the planet is to determine its relative position from the constellations and stars. For example, in the beginning of 2013, Jupiter was visible in the southeastern night sky near the star Aldebaran in the constellation of Taurus where it can be seen until the end of May. The Sun's glare will mask Jupiter from late May until the middle of July, after which it will become visible again as it enters the constellation Gemini just north of Orion. Throughout the rest of 2013 and until mid-2014, Jupiter will travel through Gemini and can be observed southwest of its two brightest stars Castor and Pollux.

Jupiter appears brightest in the night sky when it reaches opposition to the Sun. It is also during this period when it is closest to the Earth. This happens, on average, every 398.9 days. The last time this occurred was on December 3, 2012.

It is unclear when Jupiter was first noticed by humans. The earliest record of the planet was found in ancient Babylonian texts from 800 to 700 BC in which Babylonian astronomers called it Marduk, after the Mesopotamian god and patron deity of the city of Babylon during the Hammurabi period (1800 BC). The planet was later referred to as Zeus by the ancient Greeks and Jupiter by the Romans.

On January 7, 1610, the astronomer Galileo Galilee trained his telescope on Jupiter and was the first person to observe the planet's four largest moons: Io, Europa, Ganymede and Callisto. These four moons are also called Galilean satellites after their discoverer. In 1664, the English physicist Robert Hooke was the first to notice a big red spot on Jupiter's surface. This spot later became known as the Great Red Spot and is still visible to this day, which makes it at least 350 years old.

Nothing more was learned about Jupiter until The United States' National Aeronautics and Space Administration (NASA) launched several spacecraft missions to the planet and beyond starting in the 1970s. Its first mission to Jupiter was launched in March 1972 with the spacecraft Pioneer 10. Pioneer 10 was the first man-made object to cross the asteroid belt and also the first one to take images of Jupiter, which it accomplished on November 6, 1973. In April 1973, NASA launched Pioneer 11, which arrived in Jupiter's vicinity on September 1979. The spacecraft sent back the first detailed and close-up photographs of Jupiter's Great Red Spot. In 1977, two spacecrafts were launched to study Jupiter and its many moons: Voyager 2 in August followed by Voyager 1 in September. The two missions sent back photographs that revealed that, among other things, the Great Red Spot was actually a complex storm of gases and that the Jovian moon Io had many active volcanos on its surface. The Voyager 1 spacecraft also discovered faint rings surrounding the planet. In December 1995, the spacecraft Galileo arrived in Jupiter. Unlike its predecessors, which only orbited the planet, Galileo had a probe as well as being an orbiter. The probe was dropped into Jupiter to study its atmosphere while the orbiter continued research into Jupiter's moons. Galileo was also the only spacecraft that had a direct view of Jupiter when the comet Shoemaker-Levy crashed into the planet in 1994. The spacecraft's mission was concluded in September 2003. NASA's latest mission to Jupiter, named Juno, was launched in August 2011. It will study how the planet formed by investigating its atmospheric structure and measuring its gravity field and magnetic field. The spacecraft is expected to arrive at its destination in July 2016.