Is it true that Jupiter and Saturn are just gases and if so, why do they spin like earth?

Question

Why do we talk about the surface of jupiter as though it had a hard core? Where does Saturn's shadow come from if it's just a gas? I need to understand.

Answer 1

Jupiter has a low density (1.3 g/cm3), being composed primarily of hydrogen and helium. Its composition indicates that, like the Sun, it formed by gravitational collapse of part of the primeval solar nebula. It is so hot that there is no solid surface under the atmosphere, just a gradual transition from gas to liquid. Jupiter has a rocky core about 10 to 15 times Earth's mass, surrounded by a massive mantle of liquid metallic hydrogen. (At the temperature and pressure of Jupiter's interior, hydrogen is a liquid.) Liquid metallic hydrogen consists of ionized protons and electrons, so it is an electrical conductor. Jupiter's rotation and currents within the metallic hydrogen interior generate a dipolar magnetic field 4000 times stronger than Earth's. The mantle probably also contains some helium and traces of water, ammonia, methane, and other organic compounds.

Saturn, like Jupiter, is composed primarily of hydrogen and helium. Current models of the interior indicate that below the relatively thin, opaque cloud layers is a large, clear hydrogen-helium atmosphere. The cloud layers are similar to those on Jupiter: ammonia ice in the upper layer, crystals of a compound of ammonia and hydrogen sulfide in the middle layer, and water ice in the lower layer. As on Jupiter, the density of the atmosphere gradually increases toward the surface, and the gas transforms into a liquid. At the center, the hydrogen becomes metallic; Saturn, however, with its lower mass and internal pressure, has a much smaller region of metallic hydrogen than Jupiter. Saturn has a strong dipolar magnetic field similar to Jupiter's, but it is only about one-third the size. Saturn's magnetic field traps charged particles coming from the solar wind, which impinge on the ionosphere and create airglow emissions. The core is much like Jupiter's, consisting of metal, rock, and ice.

Gas planets create a shadow because the gas is opaque, not clear.

They spin due to the conservation of angular momentum and, don't forget, they do have solid and liquid cores, the same as the Earth.

Answer 2

Gas is just as real and substantial as water and rock. You are just thinking of gas as a thin, clear, almost nothing thing. It seems that way to you on Earth where the air seems thin almost to the point of being nothing. But really air is quite substantial. It can support heavy airplanes and big balloons and moving air can blow the roof off of buildings and push sailboats along and so forth. And that is just low pressure air. Jupiter has low pressure gas at its visible surface, but then there are clouds in that air, which makes what we see as the surface, and deeper inside the pressure goes up. The gas pressure deep inside a gas giant planet is so high that you cannot imagine it. The air becomes very thick as a result. It can be more like water when it gets thick enough. And in the core it is thought that there could even be a kind of "solid" gas, like metallic hydrogen.

Answer 3

Both Jupiter and Saturn have so much gas in their make up that the gas is compressed by gravity to a point where the gases at the bottom are solid. In fact it is accepted that Jupiter's gravity is so strong that hydrogen on its surface has become a metal.

Answer 4

It is supposed that all planets have formed from a primordial revolving disk of hot gases known as the solar nebulla,the sun having formed in the centre of the disk.The rotation(as well as revolution) has also originated at the time they formed.So,at the time of formation all were spinning masses of gases only.Later some of them got solidified whereas some still remain as spinning masses of gases.

Answer 5

Maybe their atmosphere is mostly comprised of gases, but make no mistake, the planets themselves have huge masses.

Answer 6

You really need to see this animation:

http://www.space.com/images/129_2.gif

...see had fluid Jupiter is; it is anything but a solid.

Gravity keeps everything bound together.

Answer 7

Gas, like solids and liquids, is matter and has mass & momentum.

Answer 8

There is a core but it is so deep that we don't know much about it.