WASP-12b as a prolate, inflated and disrupting planet from tidal dissipation

TL;DR

WASP-12b is a highly distorted, inflated Jupiter-mass exoplanet experiencing mass loss and tidal disruption due to its close proximity to its host star, with observable signatures of its prolate shape and potential circumstellar material.

Contribution

This study provides the first detailed analysis of WASP-12b's prolate shape, mass loss rate, and tidal dissipation effects, highlighting its ongoing disruption and observational signatures.

Findings

WASP-12b is losing mass at approximately 10^-7 MJ per year.

The planet's shape is significantly distorted, affecting its light curve.

A tenuous disk of tidally stripped gas may produce detectable CO emission.

Abstract

The class of exotic Jupiter-mass planets that orbit very close to their parent stars were not explicitly expected before their discovery. The recently found transiting planet WASP-12b has a mass Mp = 1.4(+/-0.1) Jupiter masses (MJ), a mean orbital distance of only 3.1 stellar radii (meaning it is subject to intense tidal forces), and a period of 1.1 days. Its radius 1.79(+/- 0.09) RJ is unexpectedly large and its orbital eccentricity 0.049(+/-0:015) is even more surprising as such close orbits are in general quickly circularized. Here we report an analysis of its properties, which reveals that the planet is losing mass to its host star at a rate ~ 10^-7 MJ yr^-1. The planets surface is distorted by the stars gravity and the light curve produced by its prolate shape will differ by about ten per cent from that of a spherical planet. We conclude that dissipation of the stars tidal perturbation in the planets convective envelope provides the energy source for its large volume. We predict up to 10mJy CO band-head (2.292 micron) emission from a tenuous disk around the host star, made up of tidally stripped planetary gas. It may also contain a detectable resonant super-Earth, as a hypothetical perturber that continually stirs up WASP-12b's eccentricity.