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?

  • 3
    $\begingroup$ What distance is the planet orbiting the star? $\endgroup$ – L.Dutch - Reinstate Monica Feb 27 at 1:39
  • $\begingroup$ Normal gas giant distance, something like Jupiter. But I guess I could ask the same question for a hot Jupiter-type planet, but that would probably be eaten by the Star when it expands into a red giant $\endgroup$ – Geroditus Feb 27 at 2:12
  • $\begingroup$ This question is better suited for astronomy.se, having that said if the gas giant survived the ordeal it could orbit whatever is left from the supernova like a white dwarf or even blackhole. $\endgroup$ – user6760 Feb 27 at 3:40

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.

  • $\begingroup$ Should have known you’d need less than an hour to lay hands on not one but two papers modelling the effects of supernovae on planets... $\endgroup$ – Joe Bloggs Feb 27 at 20:59

Quoting Randall Munroe:

[the] rule of thumb for estimating supernova-related numbers: However big you think supernovae are, they're bigger than that.

Here's a question to give you a sense of scale: Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

  1. A supernova, seen from as far away as the Sun is from the Earth, or
  2. The detonation of a hydrogen bomb pressed against your eyeball?

Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... by nine orders of magnitude.

Based on the above, my guess is that the gas giant will be stripped naked of all its gases and maybe even part if not all of its rocky core will sublimate under the astonishing large radiative flux which will shower it.

Then, whatever remains will be probably moving too fast to be gravitationally bound to the remaining dwarf, and would probably fly away into space, or at least on a different orbit.


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