Gas Giants of the Solar System - Jupiter
The first of the gas giants that we will look at is Jupiter, the largest planet. It takes 11 years to orbit the Sun, but it takes just under 10 hours to rotate once around its axis. Since it rotates so fast, it has winds that move at about 150 m/s. Jupiter's atmosphere consists of about 75% hydrogen and 25% helium; there are also trace amounts of ammonia, methane, and other light substances.
Jupiter is a "hot" planet because it gives off about 2½ times more heat than it takes in from the Sun. Astronomers believe that Jupiter has a solid metal-rock core at its center, similar to Earth, but much larger. It has an equatorial diameter of about 142,984 km, by contrast Earth's diameter is 12,756 km. Jupiter has a mass density around 318 Earth-masses.
Other note worthy features: The surrounding atmosphere is a metallic mixture of hydrogen and helium. On Earth, hydrogen and helium behave as gases, but the pressure is so high on Jupiter's interior that the hydrogen behaves like a metal. There is a shell of liquid molecules that surrounds this metallic hydrogen area. Other parts of the atmosphere has concentrations of ammonia and methane. This zone is about 1,000 (km) deep. Another interesting feature is temperature; it varies widely. For example, it goes from -130°C at the top of the clouds, to 30°C about 70 km (43 miles) below, then to about 20,000°C at the planet's center.
The image below points out some features of the atmosphere. Notice the trace compounds at the top of the cloud layer. As you go deeper, there is a zone of fluid molecular hydrogen that extends about 20,000 km (12,427 mi). There is a transition zone that is about 40,000 km (24,854 mi). In this zone, the liquid hydrogen, in molecular form at these levels is compressed until it reaches a fluid metallic state.
Finally, 60,000 km (37282 mi) down, at the center of Jupiter is a small rocky core (about 15 times the mass of the Earth). It may have been residue from the icy-dust particles that collected in an early solar nebula. It has a temperature about 20,000°C, 36,000°F.
More information about Jupiter can be found here: Interesting Facts About the Planet Jupiter.