The Mysterious Shape of Jupiter: Why Gas Planets Stay Spherical

In summary, the conversation discusses the shape and formation of Jupiter, which is made of gas but maintains a spherical shape due to its own gravity. The conversation also touches on the misleading term "Gas Giant", the presence of a rocky core and metallic hydrogen, and the use of different names for planetary geology.
  • #1
timothychoi
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TL;DR Summary
If Jupiter is made of gas, how can it maintain its shape without being contained in a spherical shaped container?
If Jupiter is made of gas, how can it maintain its spherical shape without being contained in a spherical shaped container?
 
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  • #2
Gravity. The lowest-energy shape for a mass of gas held together by its own gravity is a sphere.

You mustn't think in terms of lab-based definitions, such as "a gas expands to fill its container". That refers to very small amounts of gas whose self-gravity is negligibly small. A mass of gas the size of Jupiter will be held together by its own gravity.
 
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  • #3
The same goes for stars. Stars are much hotter than Jupiter but also remain close to spherical due to self-gravity.
 
  • #4
Certain shapes you see repeated many times over in nature as they are the most efficient. Anything made of gas in space or anything molton will become a sphere. Another example is a hexagon, look at how the rock cooled after a volcanic eruption at the "Giants Causeway" in Ireland. Similarly bees make hexagons as it is the most efficient way of making the hive that maximises space available for the least amount of wax used to create it.
 
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  • #5
The gas surrounding Jupiter is held in by the same force that keeps our atmosphere around the Earth. Our atmosphere is held in quite firmly and Jupiter's even more so, due to the incredible mass involved.

Also, the description "Gas Giant" is a bit misleading. Its not whispy stuff all the way down. There is probably a rocky but not solid core and a large amount of liquid 'metallic hydrogen' above it. This link gives a description of the likely arrangement.
 
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  • #6
sophiecentaur said:
The gas surrounding Jupiter is held in by the same force that keeps our atmosphere around the Earth. Our atmosphere is held in quite firmly and Jupiter's even more so, due to the incredible mass involved.

Also, the description "Gas Giant" is a bit misleading. Its not whispy stuff all the way down. There is probably a rocky but not solid core and a large amount of liquid 'metallic hydrogen' above it. This link gives a description of the likely arrangement.
I guess I should have read down to this post before I did some internet "research". I originally struggled to see how Jupiter could exist without a solid core. What I found matches what you posted.
 
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  • #7
There's a certain logic to Jupiter's form. If you take a mass of general 'gas and stuff' (part of the primordial nebula from which the Solar System was formed) equal to Jupiter's mass, all the more dense stuff will end up in the middle, displacing the lighter gas etc. The total mass and the proportions of all the stuff in it will determine its radius.
I still think it's incredibly smart how the details of a structure like that are deduced, when you realize that, so often, there is evidence, later that confirms it all.
 
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  • #8
sophiecentaur said:
Also, the description "Gas Giant" is a bit misleading. Its not whispy stuff all the way down. There is probably a rocky but not solid core and a large amount of liquid 'metallic hydrogen' above it. This link gives a description of the likely arrangement.
Research in the following decade confirmed this view, for example this paper based on Juno data. However, in an effort to resolve conflict between Juno and Galileo observations, these authors "confirm that Jupiter’s structure must encompass at least four different regions: an outer convective envelope, a region of
compositional, thus entropy change, an inner convective envelope and an extended diluted core enriched in heavy elements, and potentially a central compact core". [Emphasis added]

Aside: it would be preferable to describe the core as enhanced with heavy elements derived from rocky antecedents rather than "rocky". (Excuse the geological pedantry - its genetic.)
 
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  • #9
Ophiolite said:
(Excuse the geological pedantry - its genetic.)
Bring it on. Where would we be without a bit of pedantry? :smile:
I guess you bridled at my use of the term "stuff" but it seemed to fit here.
 
  • #10
Ophiolite said:
Excuse the geological pedantry - its genetic

Technically, wouldn't it be zeusological? :wink:
 
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  • #11
Diological - very irregular noun (Zευς, Zευ, Δια, Διος, Διι).
 
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  • #12
Vanadium 50 said:
Technically, wouldn't it be zeusological? :wink:
Jovian? Zeusological sounds so close to zoological, by Jove. :cool:
 
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  • #13
Lemme out of here! :headbang:
 
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  • #14
sophiecentaur said:
Bring it on. Where would we be without a bit of pedantry? :smile:
I guess you bridled at my use of the term "stuff" but it seemed to fit here.
No, I liked the stuff. I'm all for stuff! Stuff is good. It was calling it rock, when it's lost all rock like attributes, that kept nagging at me, till I resolved it with the post. :)

Vanadium 50 said:
Technically, wouldn't it be zeusological? :wink:
Perhaps, but geologists have a plan to take over the Universe, one planet at a time.
 
  • #15
Ophiolite said:
Perhaps, but geologists have a plan to take over the Universe, one planet at a time.
And they will need a different name for themselves for each planet they take over. Poor planning, imo.
 
  • #16
Partial planetary table using Roman names.

Planet​
modifier​
Mercury
Venus
Earth
Mars
Jupiter
Saturn
mecurial
venusian
terran
martian
jovian
saturnine
 
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  • #17
Wot no Vulcan?
 
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  • #18
mjc123 said:
Diological - very irregular noun (Zευς, Zευ, Δια, Διος, Διι).
That is impressive. Where did you come across those forms?

Easily confused with θεός in the genitive there.

My Greek is ancient and poorly preserved.
 
  • #19
Jupiter is not a sphere; it is an oblate spheroid. It has been bloated at the equator by its own rotation.

Same goes for Saturn.
And - not to put too fine a point on it - Earth too.
 
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  • #20
Klystron said:
Jovian? Zeusological sounds so close to zoological, by Jove. :cool:
If you're going with Latin, instead of Greek, Jovian corresponds to Terran. 😉
 
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  • #21
The Latin adjective tends to be used with general reference to the planet (the Martian atmosphere, the Jovian satellites etc.). The more specific analogy with geology tends to use the Greek form, e.g. selenology (the "geology" of the moon), areology (Mars). Proceeding by analogy, I suppose we would have hermology, aphroditology, diology, kronology (not to be confused with "chronology"), ouranology, poseidonology, and plutonology (perhaps also charonology). Oh yes, and hephaestology for Vulcan...
 
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  • #22
Pluto is Roman. It's also been unfriended from the list of planets, but that's another story. Hadenology?
 
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  • #23
Vanadium 50 said:
It's also been unfriended from the list of planets
HaHaHa 😄
 
  • #25
 

1. What causes Jupiter to have a spherical shape?

The spherical shape of Jupiter is due to its massive size and strong gravitational pull. As the gas planet formed, its own gravity caused it to collapse into a spherical shape, just like how a droplet of water in space will naturally form into a sphere due to its own gravity.

2. Why do gas planets like Jupiter stay spherical while other planets have different shapes?

Unlike rocky planets, gas planets like Jupiter do not have a solid surface. This means that there is no resistance to the planet's own gravity, allowing it to maintain a spherical shape. On the other hand, rocky planets have a solid surface that can withstand gravity and maintain different shapes.

3. Can the shape of Jupiter change over time?

While Jupiter's shape may appear to change due to its fast rotation and changing cloud formations, the overall spherical shape is maintained due to its massive size and strong gravitational pull. However, the planet's shape can be slightly altered by external factors such as collisions with other objects or changes in its atmosphere.

4. Are there any other factors that contribute to the spherical shape of Jupiter?

In addition to its size and gravity, Jupiter's high internal pressure also plays a role in maintaining its spherical shape. The intense pressure from the planet's massive atmosphere pushes towards the center, resulting in a spherical shape.

5. Do all gas planets have a spherical shape?

While most gas planets in our solar system, including Jupiter, Saturn, Uranus, and Neptune, have a spherical shape, there are some exceptions. For example, the gas planet Haumea has an ellipsoidal shape due to its fast rotation, and exoplanets have been discovered with a variety of shapes. However, spherical shapes are the most common among gas planets due to the reasons mentioned above.

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