Jupiter

Jupiter is a gas giant. This means that it has a huge atmosphere, a liquid mantle, and a liquid / solid core, with no definite boundary between the layers.

The core of Jupiter is probably composed of liquid rock, at a temperature as high as 24,000 K (43,000 °F). The core is small relative to the planet, about 20% of its radius, but it is still fifteen times heavier than the Earth.

Next comes a layer of liquid hydrogen that is under the pressure of 10,000,000 Earth atmospheres. This changes the nature of the hydrogen in such a way that it is able to conduct electricity as metal does, so it is called "metallic hydrogen." This generates the planet's magnetic field which is 20,000 times stronger than Earth's. This layer also makes up most of the planet

The layer on top of this is ordinary liquid hydrogen. This composes the upper 25% of the planet.

Next, the hydrogen thins out into the gaseous atmosphere which is 1000 km (620 miles) deep. It is composed mainly of hydrogen and helium with trace amounts of methane, water, ammonia, and hydrogen sulfide. Some scientists believe that there are also polysulphur compounds and phosphine which lend their colors to the clouds. Jupiter's Rings

Jupiter also has a faint ring system. It is comprised of one main ring, with fuzzier "gossamer" rings farther out. The system is only a few thousand kilometers from the sharp outer edge to the inner fuzzy edge which continues to the planet's atmosphere. The picture at left was taken by the Galileo spacecraft when the sun was behind Jupiter, so the rings were backlit.

Jupiter is basically one big atmosphere - as far as we know, there is no real surface to the planet. Because it is too small to be a star, no processes of fusion exist to change its composition as has occurred in the sun. Many astronomers believe that Jupiter's composition reflects the initial composition of the solar nebula. Its composition is nearly all H₂; the rest is approximately:

Besides this, aerosols of ammonia ice, water ice, and ammonia hydrosulfide exist in the atmosphere.

The temperature at 1 bar is approximately 165 K, and at 0.1 bar it is 112 K. The density at 1 bar is 160 g/m³. Below 30° latitude, wind speeds range up to 150 m/s, and above that only 40 m/s. The scale height of the Jovian atmosphere is about 27 km.

On March 25, 1993, comet P/Shoemaker-Levy 9 was discovered. Orbital calculations soon showed that it was on an impact course with Jupiter. Impact was predicted to take place during a 5 1/2 day period in July 1994.

Several Impact Sites on Jupiter of Comet P/Shoemaker-Levy 9

The comet fractured into abour two dozen pieces between 1992 to its final impact in 1994; when it was initially discovered, it was determined that there were 20 fragments. The comet was believed to have originally been a 2.3 km diameter body that was broken and captured by Jupiter during a close encounter in 1992.

The first fragment, A, impacted at 05:32 EDT on July 16, 1994, and the barrage of other fragments continued for another six days. The impacts caused giant atmospheric disturbances, as evidenced by the true-color HST image on the right. This image shows the folowing impact spots, from left to right: E/F, H, N, Q1, Q2, R, and D/G. The original image had a resolution better than 200 km/px, and it is a 3-color composite of images at 9530 Å, 5500 Å, and 4100 Å.

The first one is its immense size. It is indeed, as its name suggests, the king of the planets. About 1,320 Earths could fit inside of it.
The second characteristic is the Great Red Spot. This is a gigantic (three Earth diameters) storm that has existed for more than three centuries (Galileo discovered it in the seventeenth century). It will probably continue to exist for hundreds or thousands of years, for it is constantly being fed by smaller eddies surrounding it, such as the white spots in the picture at the right.
The third characteristic is its many moons. Jupiter has the most moons of any planet in the solar system: .
Another interesting property of Jupiter is how it generates heat. As seen in the table below, the average temperature of Jupiter is approximately 160 K. However, due to the equation for thermal equilibrium (below), it should only be about 100 K. This extra heat is generated due to gravitational contraction - the planet is slowly shrinking in diameter. This way, by compressing by only a few millimeters every year, it can generate heat by increasing the pressure of its constituent gas.

Jupiter is named after the Roman god of lightning, who was also the King of the gods. Jupiter is definitely king over the planets, for it is so big that the next-smallest planet, Saturn, could fit in it more than one and one half times.