Corot-7b a Super-Earth or a Super-Io ?

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Corot-7b a Super-Earth or a Super-Io ?

Post by exoplanet on 9th December 2009, 8:48 am

CoRoT-7 b: Super-Earth or Super-Io?

http://fr.arxiv.org/abs/0912.1337


CoRoT-7 b, a planet about 70% larger than the Earth orbiting a Sun-like star, is the first-discovered rocky exoplanet, and hence has been dubbed a "super-Earth". Some initial studies suggested that since the planet is so close to its host star, it receives enough insolation to partially melt its surface. However, these past studies failed to take into consideration the role that tides may play in this system. Even if the planet's eccentricity has always been zero, we show that tidal decay of semi-major axis could have been large enough that the planet formed on a wider orbit which received less insolation. Moreover, CoRoT-7 b could be tidally heated at a rate that dominates its geophysics and drives extreme volcanism. In this case, CoRoT-7 b is a "super-Io" that, like Jupiter's volcanic moon, is dominated by volcanism and rapid resurfacing. Such heating could occur with an eccentricity of just 10^-5. This small value could be driven by CoRoT-7 c if its own eccentricity is larger than ~10^-4. CoRoT-7 b may be the first of a class of planetary super-Ios likely to be revealed by the CoRoT and Kepler spacecraft.


Interestig stuff, sounds logical.
Due to the very active vulcanism Io has a huge cloud (actually a torus) of Sodium, Potassium, Sulfur and other elements around its orbit. An interesting consequence of this paper is that these clouds may be detected spectroscopically around exoplanets and thus provide a confirmation of this scenario.

Do you think this would be feasible ?

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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by ciceron on 9th December 2009, 8:53 am

I guess solar wind would do a quick work of any cloud that lingers outside the surface of that planet

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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by Sirius_Alpha on 9th December 2009, 9:58 am

Detecting ejected volcanic material from CoRoT-7 b? Could be extremely challenging. With the high mass of CoRoT-7 b, the escape velocity could be fairly high, so such material may not actually escape the planet. There may be no torus to detect.

But if there is, that would be a load of fun, and would amount to spectroscopically probing the interior of the planet. I would figure it would be possible if the concentration is sufficiently high.

Heck maybe if the planet's atmosphere is dominated (or perhaps replenished) by volcanically ejected material, then perhaps all that's needed is to detect the atmosphere like how it's done with HD 209458 b and HD 189733 b. Making that detection would be extremely hard though, given the small transit depth, low S/N, and all.

Maybe a task for the next generation of telescopes.

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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by Lazarus on 9th December 2009, 4:17 pm

Well sodium was among the first elements to be detected in a hot Jupiter atmosphere, it may well be that the extended "rock vapour" atmospheres of super-Ios are detectable - these are probably on average richer in alkali metals than a hot Jupiter atmosphere.
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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by AVBursch on 9th December 2009, 5:16 pm

COROT-7b would definitely be one of the most volcanically active terrestrials known. Other contenders would be HD 40307b and 55 Cancri e. With a much larger mass than Earth, the planet would have much greater internal heating, and that's before factoring in tidal heating. The term "Super-Io" woud definitely be apt here because of the high geological activity. However, volcanic material would not escape from the planet -- COROT-7b has an escape velocity of ~67000 km/h (compared to 9208 km/h for Io). Even on Earth, volcanic material does not escape into space. Once tidal heating is factored in, i coild imagine volcanic eruptions of VEI-9 taking place on the planet on a routine basis, whereas VEI-9s never happen on either Earth or Io.

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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by Lazarus on 9th December 2009, 5:51 pm

Well the eruption plumes themselves would not escape into space, but the activity would likely contribute to a "rock vapour" atmosphere - the daylight side of this planet is much hotter than any of the terrestrial planets in our system, and a magma ocean seems likely even without the effects of tidal heating. The escape velocity of the hot Jupiter around HD 209458 is around 150000 km/h, yet still evidence for atmospheric loss has been detected, so it seems likely that losses occur from the atmosphere of COROT-7b.
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Re: Corot-7b a Super-Earth or a Super-Io ?

Post by exoplanet on 9th December 2009, 7:40 pm

Hi,

The idea that atoms from the eruptions on CoRoT-7b can be detected assumes of course that some of this material eventually escapes into space. While the surface gravity of the planet is much larger than that of Io, the thermal velocities of the atoms in the vulcanic plumes of CoRoT-7b will certainly be extremely high given the amount of radiation the planet receives from the star. The analogy with Io ends here, of course.

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Re: Corot-7b a Super-Earth or a Super-Io ?

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