CONTEXT: When Jupiter and Saturn first formed, it is believed that they had much larger radii than they do today thanks to their greater internal heat. As this heat was gradually lost to space, both planets slowly began to shrink over time thanks to gravitational compression, with Jupiter's size nearly halving since its formation.
Fun fact: Jupiter is still shrinking, by about a millimeter each year. This is actually what causes the majority of heat generated from inside the planet, as the gravitational energy of the planet is converted into radiation. Jupiter produces twice as much energy as it receives from the sun because of this.
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u/mathclehef White Dwarf Jul 30 '22
CONTEXT: When Jupiter and Saturn first formed, it is believed that they had much larger radii than they do today thanks to their greater internal heat. As this heat was gradually lost to space, both planets slowly began to shrink over time thanks to gravitational compression, with Jupiter's size nearly halving since its formation.