To the extent that Kepler’s laws are exact only for two-body systems of point masses (so I guess calling Kepler’s third law the ground truth is a bit problematic) and to the extent that the data are imperfectly observed, there are residuals that over-eager models can try to match.
Edit: More generally, you don’t overfit the underlying law, you overfit noisy data generated by the underlying law.
To the extent that Kepler’s laws are exact only for two-body systems of point masses (so I guess calling Kepler’s third law the ground truth is a bit problematic) and to the extent that the data are imperfectly observed, there are residuals that over-eager models can try to match.
Edit: More generally, you don’t overfit the underlying law, you overfit noisy data generated by the underlying law.
Kepler’s law holds well. The influences of other planets are negligible for the precision we dealt with.