If they don’t have a solid core, where do they create their gravity to hold all the gasses into a planet shape? I’ve never understood this.
In: Physics
Funnily enough, we don’t actually know if gas giants have solid cores or not! However, more planet formation theories do use some sort of rocky core (protoplanet). Once that core reaches a certain mass, it starts to accrete enough gas that the gas mass helps it accrete more gas–a process called runaway accretion. This can pump up a small core from ~10 times the mass of Earth to Jupiter size or larger!
There are also theories of direct fragmentation, where gas can collapse in on itself and form a planet directly without a core required. This pathway is more akin to stellar formation and requires very massive protoplanetary disks.
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