http://arxiv.org/abs/2111.08273
WASP-12b stands out among the planets of its class of hot Jupiters because of the observed fast orbital decay attributed to tidal dissipation. The measured rate of the orbital period is $\stackrel{\bf\centerdot}{\textstyle{P}}{\rm orb}\,=\,-\,29\pm3\;\mbox{ms/yr}\;$=$\;(9.2\pm1.0)\times10^{-10}\;\mbox{s/s}$. In the literature heretofore, all attempts to explain this high rate were based on the assumption that the orbital evolution is dominated by the tides in the star. Since the modified tidal quality factor in yellow dwarfs is insufficient to warrant such a decay rate, a hypothesis was put forward that the star may actually be a subgiant. Using the latest data from the Gaia mission, we estimate the mass of WASP-12 at $1.28\,{M{Sun}}$ and point out that it takes at least $600~\mbox{Myr}$ to evolve off the main sequence to its present state, which is roughly 20 times the inferred dynamical lifetime of the planet. The previous research neglected the tidal dissipation in the planet assuming it to be negligible due to the likely synchronisation of its rotation and a presumed high quality factor. We critically reassess this assumption in the light of recent astrometric results for Jupiter and Saturn, also employing more advanced theories of frequency-dependent tidal dissipation. Assuming that WASP-12b, like our Jupiter and Saturn, has a solid core, we find that the observed orbital decay is well explained by the tides in the planet. We calculate the exact value of the modified quality factor from the observed orbital decay and the upper bound eccentricity, which happens to coincide almost precisely with that of our Jupiter.
M. Efroimsky and V. Makarov
Wed, 17 Nov 21
6/64
Comments: N/A