HYDROSTATIC_SPIN_LIMIT

The spin, as a fraction of gravity at the equator, that a planet's draw is floored at: q = ω²R³/GM, so this is the shortest day a body of that mass and size is allowed.

Saturn is the fastest known relative to its own breakup, at 0.155, and a planet drawn at six hours with a giant's density would sit at half a gravity — a body that is shedding its equator rather than holding a figure, and drawn as a lens with rings through it. A fifth is a little past Saturn: a giant at the limit comes out about a seventh flattened with the class factor above, which is visibly a fast rotator and still a planet.

universe/src/system.ts:1037