Jupiter, Zeus, the god of Olympus, is 773 million km from the Sun, 5 times farther than the Earth and revolves around the Sun in just over 11 years. It turns very fast on itself: in 9h55 min against 24 hours for the Earth. Jupiter is the largest planet in the solar system. It is entirely composed of gases: hydrogen and helium like the Sun with a little methane and ammonia at the top of the atmosphere forming its famous colored belts. There are generally three dark belts more or less thick and colored in each hemisphere.
Jupiter is surrounded by colored clouds whose temperature at the top of the atmosphere is about -160 ° C. At the telescope his disc has broad alternating bands of light and dark. The light areas are 20 km higher than the dark belts and are also 9 ° C colder. Since Jupiter does not have a solid surface like the Earth, as can be seen in a telescope or telescope, its globe is flattened at the poles, the equator being 10% wider than the distance from a pole to the other.
The southern hemisphere also contains a huge permanent high that has been called the Great Red Spot because of its color. This spot is twice as big as the Earth. It turns on itself and sometimes becomes clearer but it never disappears; it has been around for over 400 years! It is largely unknown which mechanism remains in place without dissipating.
But even if it is composed of light gases, this gas has a weight; Jupiter is so large and contains so much gas that it is 318 times heavier than Earth, which contains elements that are, on average, five times heavier than those of Jupiter.
In fact if we gathered all the planets, they would represent only 2/3 of the mass of Jupiter! It is so big that it has an equatorial diameter of 142984 km against 12756 km for the Earth; we could therefore align the Earth 11 times in the diameter of Jupiter and place more than 1000 Earth in the volume of Jupiter! It is indeed a giant planet!
In fact, on the image on the left where we see Jupiter and one of its four largest satellites, the Earth would be only twice as large as the small satellite!
Jupiter is so heavy that its nucleus undergoes a pressure of several million atmospheres which warms it from the inside: it is estimated that its nucleus has a temperature of 20000 ° C against about 5000 ° C in the nucleus of the Earth. Overall Jupiter emits twice as much heat as it receives from the sun. But it is not heavy enough to shine quite like a star. Jupiter is actually a failed star. He should have weighed even heavier to become a second sun …
Jupiter is so massive that its power of attraction does not attract a single satellite like the Earth and the Moon but it is surrounded by at least 69 satellites! Four are almost as big as the moon; they are Ganymede, Callisto, Europe and Io. We can easily observe them in a small telescope like small, bright, star-like dots around Jupiter. You’ll see them move in minutes.
Of all its satellites, most resemble the moon and are riddled with craters. They are often frozen and covered with ice. Only Io is still active. Measuring 3640 km in diameter, its surface is covered with about 300 volcanic craters (caldera) about 40 km in diameter. A dozen of them constantly spew out lava and sulfur, giving the surface of Io a yellow-orange color reminiscent of a pizza, which is also nickname that astronomers gave to Io.
Finally, in 1979 astronomers discovered three very thin and very dark rings around Jupiter. They have an average width of 6500 km for only 30 km thick. They consist of small icy stones. But this ring is invisible in a small telescope. The ring of Saturn is 10 times wider and 100000 times denser.