Like, how is that possible? Is actual gas? Can I get to the other side of it just going through it? And more importantly, how the hell does all of that mass stay together if it’s gas? Wasn’t is supposed to just spread and try to occupy the maximum volume possible?
In: Physics
When we say a planet is a gas giant we are indicating that most of the planet is made up of elements or compounds that are gases on Earth under standard conditions.
These explanations are good, but the planet is lacking the ability to make “rock” as well. There’s much more to it than that, but you asked ELI5.
> Wasn’t is supposed to just spread and try to occupy the maximum volume possible
Sure, but gravity is a thing, and gas giants have a *lot* of it. Gas still obeys gravity, and as the gas becomes less and less dense the further up and up you go the gas doesn’t have enough pushing it up away from the planet to overcome the gravitational force pushing it down. Gas trying to get away will (in many cases) just go in an arc and fall back down.
Gas tries to spread out yes, but the keyword is tries. On the scale of planets (and stars) the gas is compressed and held in place by it’s own gravity.
Like air on Earth mostly stays on Earth because of the gravity. Earth doesn’t have more air/gas than the gas planets though because the sun basically blows it away. Farther away from the sun there is less force from the sun and the gas collects into planets.
Also gas planets are only gas at the surface. Once you go far down enough the pressure increases to the point that you have liquid. Also the the gas planets do have solid cores. Jupiters rock core for example is still several times larger than Earth.
The planet *is* made of gas, usually heavier gases with a very small, very dense metal core to produce the amount of gravity needed to hold everything together. You could theoretically go through it, just not straight through the center. Think of it as a planet that’s mostly atmosphere instead of mostly rock and dirt and stuff
The vast majority of the atoms in the universe are Hydrogen and Helium, with a large portion of the remainder bring Oxygen, Carbon, Neon and Nitrogen.
These are either gasses or predominately form elements that are gasses across a wide range of temperatures and pressures.
Gas giants are planets where most of the mass is made up of these gasses, possibly surrounding a rocky core that is small relative to the overall size of the planet.
Answering your questions in order
1. It means that the planet is made of gas
2. Gravity
3. Mostly, but if the planet gets big enough, the core becomes a super-critical fluid, something not quite gas, not quite liquid.
4. Yes, if you can withstand the pressure, fluid density, and can push your way out of the gravity well.
5. Gravity again.
6. Yes, and the maximum size is the size of the planet, because gravity keeps it there.
While it may seem like gravity only attracts small objects to big ones, everything is attracted by everything elses gravity, so if you start with a relatively small iron core that goes through a gas cloud, the attractive effect compounds, gathering more and more into itself, as long as there is gas to collect.
It means we can’t detect a solid surface on it from earth
Obviously we don’t know for sure what’s deep under the clouds.
Gravity holds the gas together. Gas spreads out normally because gas molecules act like bouncy balls and head away from each other whenever they collide, but like boucy balls their paths are bent by the force of gravity.
Some do escape into space. But some gas molecules are also caught from space to make up for it.
There are also other effects at work I can’t possibly explain to a five year old so just trust me bro.
>Is actual gas?
**No.** Gas planet is a stupid term; they are not entirely gas, not even majorly.
1. When scientists say a planet is made out of gas, what they actually mean is that it’s made out of elements that are gas under the Earth’s atmospheric condition.
2. The pressure throughout a ‘gas’ planet is too high for the ‘gases’ to remain as the form of gas.
3. In fact, most of them are neither liquid nor gaseous, but *supercritical*. Due to extreme pressure and temperature, the phase of the ‘gases’ is above their thermodynamic critical point. This means that their physical properties such as density, viscosity, diffusivity, etc are distinctively different relative to when they are in liquid or gaseous phase (but somewhere in between; the properties can be tuned continuously by varying pressure & temperature. This is not possible for discrete phases such as liquid or gas.)
Gas is both held in place and compressed by gravity. You live in the bottom of an “ocean” of gas! All the gas above you is pressing down on you; you can get a sense of how hard it’s pressing down by blowing up a balloon. You’re pushing air up to make space for the inflated balloon, in a sense. The air in a gas planet gets to much stronger pressures as you get closer to the center.
Latest Answers