tidal dissipation inflates WASP-12b ?

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tidal dissipation inflates WASP-12b ?

Post by exoplanet on 24th February 2010, 6:02 pm

In Nature

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

Shu-lin Li1,2,4, N. Miller3, Douglas N. C. Lin1,3 & Jonathan J. Fortney3

Kavli Institute for Astronomy and Astrophysics,
Department of Astronomy, Peking University, Beijing 100871, China
Department of Astronomy and Astrophysics, University of California, Santa Cruz 95064, USA

The class of exotic Jupiter-mass planets that orbit very close to their parent stars were not explicitly expected before their discovery1. The recently discovered2 transiting planet WASP-12b has a mass M = 1.4 Ī 0.1 Jupiter masses (M J), 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 Ī 0.09R J is unexpectedly large and its orbital eccentricity 0.049 Ī 0.015 is even more surprising because such close orbits are usually 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 of about 10-7 M J per year. The planetís surface is distorted by the starís 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 starís tidal perturbation in the planetís convective envelope provides the energy source for its large volume. We predict up to 10 mJy CO band-head (2.292 μm) 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-12bís eccentricity.

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Re: tidal dissipation inflates WASP-12b ?

Post by Sirius_Alpha on 24th February 2010, 6:36 pm

Wow. That will be very interesting to see confirmed.

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Re: tidal dissipation inflates WASP-12b ?

Post by exoplanet on 24th February 2010, 9:15 pm


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Re: tidal dissipation inflates WASP-12b ?

Post by Sirius_Alpha on 27th February 2010, 6:15 am

Press release article plus a very amusing graphic.

http://kiaa.pku.edu.cn/Destiny/Destiny_of_hot_Jupiters.html

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Re: tidal dissipation inflates WASP-12b ?

Post by Stalker on 28th February 2010, 2:19 am

i have some questions

Is it normal that gas makes a disc around the star and not a tail behind the planet? Why? It is explained in the paper, but why it does not arrive at HD 209458 b for example?


Why the gas is drawn in front of the planet and not behind? Should not he be evicted by the pressure of light and of wind of the star?

In a Sudarsky's like classification, what should resemble this planet?
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Re: tidal dissipation inflates WASP-12b ?

Post by Sirius_Alpha on 28th February 2010, 2:54 am

Stalker wrote:Is it normal that gas makes a disc around the star and not a tail behind the planet? Why?
Yes, this is normal. The expelled matter interacts with itself and the planet and looses speed. It's easier to fall toward the star than to oppose the gravitational gradient.

Stalker wrote:Why the gas is drawn in front of the planet and not behind? Should not he be evicted by the pressure of light and of wind of the star?
Stellar irradiation causes atmospheric escape, leading to an envelope of escaped material around the planet. The star tidally distorts this exosphere into a teardrop shape. With the vertex of the teardrop at the L1 point. This location becomes a nozzle for which gas to escape toward the star. I suspect hydrogen does not get pushed out of the system by solar wind fast enough for it to make a significant difference in the disk density. Moreover, the material in the disk falls toward the star.

Stalker wrote:In a Sudarsky's like classification, what should resemble this planet?
Class V.


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Re: tidal dissipation inflates WASP-12b ?

Post by Lazarus on 28th February 2010, 6:22 am

Regarding the mass loss inwards through L1 instead of being driven outwards by the solar wind, from the supplementary information:

The windís ram pressure Ṁwvm/4πa2 on WASP-12bís dayside could potentially exceed the planetís atmospheric thermal pressure and perturb the flow toward the night side but it is inadequate to push the gas to overcome the gravitational potential difference 2GM*/3a between L1 and the outer Lagrangian point at L2.
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