Starship Asterisk*

Presumably, the mass that is "boiling away" is doing so because it is gaining kinetic energy from the star's radiation. The KE of the remaining mass should be unaffected...I would think. Also, I think the discussion of gas boiling away is not due to observations, but due to computer modelling of these hot Jupiter systems, but it seems like a very reasonable result.

Astro_uk, you raise an interesting point about friction. I believe gas giants are not expected to be able to form this close to star. Instead, they form at greater distances and migrate inward. I don't remember the proposed mechanism, but I think it was either friction in the still-condensing accretion disk.

I don't think the orbit will decay because of loss of mass, the orbit of an object is totally independent of the mass of the object. Thats why we can build satelites that have the same orbit as the Earth, as long as they have the right orbital velocity it doesnt matter what their mass is.

The decay of the orbit would be due to tidal effects, or friction against a solar envelope I would think.

We'll see if anyone else knows, but I would think that it might or at least be disintegrated or boiled away because its orbital speed wouldn't change but the kinetic energy would. As the planet looses mass, there is less kinetic energy being carried in the velocity of its orbital speed. So it should gradually decay unless there is some mechanism that could cause orbital equillebrium even with the loss of mass.

I would guess so, if there is a solid core that is. I would think that the rate of mass loss probably accelerates over time too, with less gravity to hold the gas more will be lost. Whether or not the planet would spiral into the star probably depends on how close it is. I don't really know anybody that works in planetary astronomy to ask though unfortunately.

There have been a number of "Hot Jupiter" type planets found lately. Some with orbital periods of less than 10 days. Several of these reported finds relate information that the Planet is being slowly stripped of its gas as it is blown away by the solar winds of its parent star. If the cycle completes itself, in time could the "Hot Jupiter" planet could become a hot mercury (Jupiter core) that would slowly spiral into the star?