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I already read Can a planet survive a supernova? but that just addresses some kind of planet-remnant remaining in orbit.

Parameters:

  • Binary system. One component is a Sun-like G-type star with several rocky planets, one in the habitable zone. The other is a neutron star, the remnant of a (type II) supernova from a large (maybe 12 solar masses) B-type star.

  • Early in the system's history, the high-mass star went supernova and enriched the G-type and its planets/asteroids/etc with heavy elements.

  • I need the habitable-zone planet to retain a roughly Earthlike atmospheric pressure. It's OK if the planet starts out with a Venus-like (or more) atmospheric pressure and gets knocked down to 1 atm or so by the supernova.

Questions:

So, how much does the separation of the Sunlike star from the supernova-ing star need to be for the atmosphere to survive?

At that distance, would the habitable-zone planet be meaningfully enriched in heavy metals by matter ejected from the supernova?

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    $\begingroup$ See this answer - 8 parsecs would damage atmosphere, but wouldn't destroy it. I wasn't able to find resources more fitted for your question. $\endgroup$
    – Mołot
    Sep 3, 2016 at 7:14
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    $\begingroup$ Actually, if the planet is shielded by its star (a kind of eclipse) it could be rather close. But as the supernova generate a gas nebula, I don't see the point. If in the same system,your planet will be cooked in plasma. $\endgroup$
    – Madlozoz
    Sep 3, 2016 at 12:06
  • $\begingroup$ @Molot: That link refers just to damaging the ozone layer & nitrogen oxides. I'm not worrying about "minor" chemistry changes like that; this would happen long before the conversion of the atmosphere to an oxidizing one. I just need significant atmospheric mass to persist. $\endgroup$
    – cometaryorbit
    Sep 4, 2016 at 5:48
  • $\begingroup$ That's why I only commented. In no way it is an answer, but it gave some useful info, so I felt link is appropriate. $\endgroup$
    – Mołot
    Sep 4, 2016 at 6:00

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This isn't going to work, in this form. You need to be light years away to have an atmosphere survive, at which point the heavy metals enrichment will be insignificant. I can see a couple of different ways to achieve a planet with both life and heavy metal enrichment.

Formed quickly after the supernova

Our solar system was formed from gas and dust that includes remnants from a supernova explosion. We know this because we have heavy metals. If we knew more about exactly how they are formed in a supernova, we'd be able to date the one that formed our heavy metals. For example, we know the relative proportions of U-235 and U-238 on Earth rather accurately. That proportion is slowly changing because they are both radioactive and have different half-lives. If we knew the proportions in which they are formed in a supernova, it would be easy to calculate how long ago the supernova happened.

If your planet formed fairly quickly after your supernova, and developed life quite quickly, it's possible to have a life-bearing planet with a high abundance of heavy metals.

Replace the atmosphere and oceans

The supernova happened, and you're left with a rocky planet orbiting the companion star. It used to be a gas giant, but it got crispy-fried, down to its rocky core. Heavy elements got deposited on it. Everything went quiet for a while.

A few million years later, the star system has an encounter with a stellar nursery and blunders through the Oort clouds of a bunch of new solar systems. Lots of those icy bodies hit your planet, giving it a new set of water and gasses. Life restarts, after a while.

As a parallel, Earth's water has to have been added after the planet formed: it's too volatile to have stayed on Earth during the initial collisions that formed the planet. The water seems to have been added in the later stages of the Late Heavy Bombardment, see the Wikipedia article on Formation and Evolution of the Solar System#Asteroid Belt. So this is just a repeat of that process, on a planet that had been sterilized by your supernova.

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  • $\begingroup$ Of course, using the relative proportions of U238 and U235 to date the supernova from whose remnants the Earth formed assumes that only one such supernova was involved. $\endgroup$
    – EvilSnack
    Sep 3, 2016 at 17:08
  • $\begingroup$ Indeed, although it's a reasonable starting hypothesis. There are several such decays that can be used for dating, and since they involve different half-lives, they'll give inconsistent results if there was more than one supernova involved. I didn't want to go into that much detail in a side example. $\endgroup$
    – John Dallman
    Sep 3, 2016 at 17:46
  • $\begingroup$ OK, thanks. On the "formed quickly" part - would it work if the supernova star was really short lived (a couple of million years) and planet formation wasn't complete yet in the companion system? Or would the protoplanetary nebula get completely blown away at, say, a tenth of a light year? $\endgroup$
    – cometaryorbit
    Sep 4, 2016 at 5:33
  • $\begingroup$ I think the nebula would get blown away. Supernovae are astonishingly powerful: this xkcd what-f has some numbers. $\endgroup$
    – John Dallman
    Sep 4, 2016 at 6:27
  • $\begingroup$ OK, thanks. Looks like I'll go with the replacement of water/gases then. (And accepted...) $\endgroup$
    – cometaryorbit
    Sep 5, 2016 at 22:48

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