What will become of Jupiter when the Sun goes red giant? Will its gases boil away? Will it vanish?
A problem with answering this question is that a lot of details concerning the Sun and Jupiter’s composition still need to be answered. This is a The Astrophysical Journal paper from 1993, detailing different scenarios for the Sun’s expansion to a red giant. (Warning, .PDF) They vary widely, depending on what parameters you choose for the Sun’s composition. As the Sun expands, it also loses mass, at times quite violently and abruptly. A lighter Sun has less gravity, and therefore Jupiter’s orbit will get further from the center of the Sun. This siteseems to think that the Solar System’s zone of habitability will expand to encompass Jupiter. How much of Jupiter will be left, I don’t know. I imagine it depends on the ferocity of the solar wind, the inertia of Jupiter’s gas layers, the distance Jupiter will be from the Sun, and a bunch of other things, during the Sun’s helium flashes. I don’t believe that Jupiter can capture enough mass from the Sun or other parts of the Solar System, even over 5 billion years, to achieve thermonuclear ignition itself. We do know that gas giants (“Hot Jupiters”) orbit large stars in other solar systems much closer than even the orbit of Mercury, so surely Jupiter won’t lose all of its gas layers to solar wind. However, see this article describing a potential gas giant remnant, orbiting within 0.02AU.
All of this though, assumes that Jupiter stays in roughly its current orbit by the time the Sun goes to sub-giant and red giant stages (roughly 5 billion years from now),
Thanks for the comprehensive answer, and the leads. This is mere curiosity, but when ya gotta know, ya gotta know!
I don’t have anything of substance to add, but that was a really good and comprehensive answer, Gray Ghost!
Wait, do we really know the so-called “Hot Jupiters” are really gas giants? Or do we just suspect they are, since they’re so massive and we don’t know of any other sorts of bodies in that mass range?
I think so. The “wobble” method makes it possible to determine their mass, while detection by occultation gives an estimate of diameter. The two together make estimates of density possible.
Edit - reading up a bit more, looks like what I said above is correct. Also, it’s possible to detect the elements in the planet’s atmosphere directly using spectroscopy.