What would happen to a gas giant during a supernova?
Fairly straightforward question. Imagine a gas giant planet, like the size of Jupiter, in orbit around a massive star. The star goes supernova.
What happens to the planet? Is the energy of the supernova enough to strip away the atmosphere, leaving just the rocky core behind? Is there a way for the planet to remain in orbit around the resulting white dwarf?
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Simulations of the dynamics of planets close to massive stars during a supernova (Veras et al. 2011) indicate that a planet in a reasonably tight orbit ($\sim2\text{ AU}$) around all but the lowest-mass supernova progenitors is almost certainly going to be ejected from the system. The cases where a planet does survive place it near periapsis, almost as far from the star as it can be. As many giant planets are hot Jupiters and thus reside only a fraction of an AU from their parent stars, the percentage of these planets that are not ejected from the system is extremely tiny. The survival rate for a planet in an orbit like Jupiter's are certainly better, but still quite slim.
Additionally, many supergiants undergo periods of extreme mass loss ("superwinds") in the stages of their lives immediately preceding a supernova. This mass loss plays a significant role in the evolution of the star and the evolution of the orbits of any planets bound to it. In fact, Veras et al. argue that it could lead to the ejection of small bodies orbiting the star even before the supernova itself occurs.
Of course, a large fraction (although not all!) of the planet's material will be stripped away by the ejecta. I haven't been able to find many good treatments modeling mass loss by the planet, but Vila et al 1980 (not the clearest or most detailed paper, I know) put together a couple grids of models of various planet masses and semi-major axes. It looks like a 1-2 Jupiter-mass planet at a couple AU around a 4-8 solar mass star could lose about 30% of its material. In addition to being flung out of the system, your planet is going to get a lot of its mass ablated away and ejected.
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