Polar Radius of Jupiter

Jupiter's poles sit 4638 km closer to the centre than its equator does, a flattening of 6.5 per cent that is plainly visible in a small telescope — the disc looks subtly but unmistakably squashed. The bulge follows from spinning the solar system's fastest rotation through a body that is mostly fluid: the planet's shape is simply the surface where gravity and centrifugal effect balance at one bar of pressure.

That shape is not cosmetic bookkeeping. The oblateness produces the gravitational harmonic J₂, which precesses the orbits of the Galilean moons and every visiting spacecraft, and the precise figure measured by Juno's radio tracking constrains what lies inside — pointing to a "fuzzy" core, rock and ice smeared through the inner half of the planet rather than packed into a discrete lump. For any calculation of what Jupiter looks like from a pole, or of gravity above one, this is the radius to use.