Abstract:The recent direct spectroscopic observation of the spin of the young gas giant exoplanet β Pictoris b was a powerful clue as to the general validity of the trend of the planetary spin with the mass even outside the Solar System. Nevertheless, the spin-mass relationship, which looks like to hold irrespective of the planet composition and radius, is admittedly poorly understood. On the basis of bilogarithmic regressions, the rotational kinetic energy is found to explain the available data more significantly than the equatorial rotation velocity but no more than the spin angular momentum; nevertheless, only the rotational energy turns out to be closely proportional to the square of the mass of planets, suggesting its possible close and direct ties to the planetary mass by means of some fundamental processes. The hypothesis is made that such underlying physical processes can be described by the non-gauge cosmological theory of byuons, which proved useful to explain other astrophysical and geophysical puzzling phenomena such as the motion of pulsars, the nature of dark matter and dark energy, the anisotropy of cosmic rays and the accelerated expansion of the Universe. It's shown that the theory of byuons is able to explain the observed close proportionality of the planetary rotational kinetic energy to the square of the mass.