Jupiter is a truly amazing world. An object for which the word "planet" tends to lose the meaning that we have come to understand for the celestial bodies closest to our own world. Though they are strange and very different from the Earth, the closest planets to the Sun, such as Mercury, Venus and Mars, still have something in common with our own: the fact that they are all solid objects. But not Jupiter. No matter how well equipped, an astronaut could never set foot on the surface of Jupiter. That's because Jupiter is an immense ball of dust and gas, from the center of which extends an ocean of liquid hydrogen at a temperature of thousands of degrees and a pressure of thousands of atmospheres. Jupiter is the giant of the solar system. With a diameter of almost 143 000 kilometers (11 times greater than that of the Earth) it is the largest planet known to man: if it were an empty sphere, it could contain no less than 1 316 "balls" the size of the Earth. Its year, i.e. the time it takes to complete an entire revolution around the Sun, lasts almost twelve Earth years. Despite the dimensions, its day (the time it takes to revolve around itself) lasts less than half our own: 9 hours and 50 minutes, which means that a point at the equator turns at a speed of almost 40 000 kilometers per hour. The clouds on Jupiter contain hurricanes with a diameter from two to four times the size of the Earth, and they last for hundreds of years. Jupiter is surrounded by at least 14 moons, some of which are as large as planets. It is also enveloped by incredible electric storms, a magnetic field up to 28 times as intense as on Earth and radiation belts whose effects are even felt on our planet. And then, like Saturn and Uranus, even Jupiter has a ring. The real discovery of Jupiter, after centuries of observations from the Earth, began on December 4, 1973, when, after a 20-month journey, the first automatic probe passed within 130 000 kilometers from its surface. This probe, Pioneer 10, left the Earth in March of the previous year. In a little less than six years, three other probes traveled close to Jupiter: Pioneer 11 in 1974, Voyager 1 in March 1979 and Voyager 2 in July of the same year. Several hundred kilos of instruments and just a few days of close-up observations upset three centuries of patient astronomical research, transforming one of the numerous luminous points in the sky into a real cosmic "monster".
Jupiter is a truly amazing world. An object for which the word "planet" tends to lose the meaning that we have come to understand for the celestial bodies closest to our own world. Though they are strange and very different from the Earth, the closest planets to the Sun, such as Mercury, Venus and Mars, still have something in common with our own: the fact that they are all solid objects. But not Jupiter. No matter how well equipped, an astronaut could never set foot on the surface of Jupiter. That's because Jupiter is an immense ball of dust and gas, from the center of which extends an ocean of liquid hydrogen at a temperature of thousands of degrees and a pressure of thousands of atmospheres. Jupiter is the giant of the solar system. With a diameter of almost 143 000 kilometers (11 times greater than that of the Earth) it is the largest planet known to man: if it were an empty sphere, it could contain no less than 1 316 "balls" the size of the Earth. Its year, i.e. the time it takes to complete an entire revolution around the Sun, lasts almost twelve Earth years. Despite the dimensions, its day (the time it takes to revolve around itself) lasts less than half our own: 9 hours and 50 minutes, which means that a point at the equator turns at a speed of almost 40 000 kilometers per hour. The clouds on Jupiter contain hurricanes with a diameter from two to four times the size of the Earth, and they last for hundreds of years. Jupiter is surrounded by at least 14 moons, some of which are as large as planets. It is also enveloped by incredible electric storms, a magnetic field up to 28 times as intense as on Earth and radiation belts whose effects are even felt on our planet. And then, like Saturn and Uranus, even Jupiter has a ring. The real discovery of Jupiter, after centuries of observations from the Earth, began on December 4, 1973, when, after a 20-month journey, the first automatic probe passed within 130 000 kilometers from its surface. This probe, Pioneer 10, left the Earth in March of the previous year. In a little less than six years, three other probes traveled close to Jupiter: Pioneer 11 in 1974, Voyager 1 in March 1979 and Voyager 2 in July of the same year. Several hundred kilos of instruments and just a few days of close-up observations upset three centuries of patient astronomical research, transforming one of the numerous luminous points in the sky into a real cosmic "monster".
