Definition for Jupiter
From Biology Forums Dictionary
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 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.