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Comment by yubblegum | Hacker News Reader

I've always wondered about the core of these gas giants. I assume it is some liquid form of light elements. What is puzzling is the presence of the gas giants in the middle of solar system's planetary line up: why are they in the middle and the ones closer or further away from the central star are not like them? Is it the temperature gradient?

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I am not an astronomer (save in the very amateur sense), but I think it has to do with Jupiter forming both early in the history of solar system, and, as you guess, beyond the Sun's 'snow line'.

Wikipedia is a good place to start getting a feel for the possible history of the Solar System:

https://en.wikipedia.org/wiki/Jupiter#Formation_and_migratio...

https://en.wikipedia.org/wiki/Grand_tack_hypothesis

https://en.wikipedia.org/wiki/Nice_model

> Data from the Juno mission showed that Jupiter has a diffuse core that mixes into its mantle, extending for 30–50% of the planet's radius, and comprising heavy elements with a combined mass 7–25 times the Earth.

https://en.wikipedia.org/wiki/Jupiter#Internal_structure

> This has resulted in the theory that Jupiter does not have a solid core as previously thought, but a "fuzzy" core made of pieces of rock and metallic hydrogen.

https://en.wikipedia.org/wiki/Juno_(spacecraft)#Scientific_r...

It's made from something which can generate magnetic fields, since Jupiter has a very strong magnetic field with a lot of distinct inhomogeneous features, resulting in some interesting radio emissions:

https://www.ebsco.com/research-starters/science/jupiters-mag...

https://radiojove.gsfc.nasa.gov/library/sci_briefs/decametri...

The rotation of these features is the basis for the "system III" definition of longitude on Jupiter.

Because of solar wind. After the sun formed from the material of the proto solar system it started producing solar winds. This pushes light elements to the edge of the solar system but heavy elements stay. So rocky planets form. Then the light elements collect as well and reenter the interior solar system as comets which redeposit light elements on the surface of rocky planets. In the mean time the light elements that collected together in great quantities formed the gas planets.

This is all a very traditional view afaik and doesn’t explain where mantle light elements come from. For example there is a great deal of water that is in the mantle that drives geochemical changes in the mantle rocks. Was that there originally? Or was it put their after plate tectonics started and subduction sucked water into the mantle? I don’t know but I would assume there are plenty of geodynamics people who would have opinions more deeper than mine on the topic.

> I assume it is some liquid form of light elements.

Why would you assume that? The heavier elements such as iron are likelier to move to the center of gravity.

I'd assume these elements would be created in the sun and keep close to the sun, because of their higher mass.

All the heavier elements were created in a former star that went supernova. The solar system formed from the gas/dust after that.

The heavier elements being formed in our sun now are going to stay there until something can tear it apart.

Some will be ejected back into space when the aged Sun becomes a planetary nebula (with a white dwarf at the center).

Until several billion years in the future, our sun will create no element heavier then helium.

IIR, our sun's mass is far too low to ever create any element heavier than carbon.

The core of Jupiter is thought to contain metallic hydrogen.

Found this on the wiki for metalic hydrogen. Apprently there is a liquid phase as well. Apparently there is debate as to whether there is a solid core besides the hydrogen (thought shown in the pic):

https://upload.wikimedia.org/wikipedia/commons/b/b5/Jupiter_...

They aren't in the middle of the “planetary lineup”.

The four inner planets are all terrestrial. The four outer planets are gas (the last fwl sometimes distinguished instead as “ice”) giants.

There are dwarf planets (a separate category from, rather than sibcategory of, planets) closer and farther, but no known rocky planets beyond the gas/ice giants.

In an Arthur C Clarke story (I forget which one) the core of jupiter is a planet sized diamond.

Space Odyssey one of the sequels.

2061. Not his best work, alas.

Actually 2010, in the closing words of Chap. 38.

Though I agree that 2061 fell rather short of his usual.

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