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Say if a large enough star, that has a number of planets, were to explode in a supernova:

  1. Would any of the planets survive?
  2. Would they become rogue planets?
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    $\begingroup$ If say our Sun has enough mass to go Supernova then all the planets will be destroyed. But then the current planets(solar system) would have looked different with a large Sun in the middle. $\endgroup$ – ObiWanKenobi Oct 22 '15 at 1:21
  • $\begingroup$ My point is not of the order of planets of how the planets are currently positioned. You say that all the planets would be destroyed. Do you have any scientific evidence to back up your claim? $\endgroup$ – CipherBot Oct 22 '15 at 2:25
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    $\begingroup$ Edit your question to be not entirely unrealistic and hypothetical. A 1 solar mass star cannot become a supernova, therefore cannot be "an example" and therefore your question cannot be answered using any sensible physical arguments. If you were talking about a 10 solar mass star, maybe. But then you have to decide what kind of planetary system you are talking about. If the Earth was at 1 au from such a star, it would not have an orbital period of 1 year and would have a different potential energy within the "solar system". $\endgroup$ – Rob Jeffries Oct 22 '15 at 13:21
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    $\begingroup$ You may not care, but it affects the physics of the answer. Our system will not undergo a supernova event. You cannot write an answer that begins "If a 1 solar mass star goes supernova...", because it doesn't. Whether planets become "rogue" planets does depend on what their orbital periods are. Your question is frivolous and unanswerable beyond what is in the accepted answer -i.e. that it can't happen. The actual fate of the solar system is a different question, but often asked (and answered) elsewhere. $\endgroup$ – Rob Jeffries Oct 22 '15 at 14:32
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    $\begingroup$ Just to amplify in case you still don't get it. The details of even a hypothetical answer would need to contain: what radius the Sun attained and how much mass it lost during its evolution prior to a supernova; how much mass it lost during the supernova; what luminosity it achieved before and during a supernova; what the supernova ejecta speed was etc. etc.. You would have to tell us what those numbers (and others) are for your made up solar supernova. Further, even if you don't use the Sun, you still need to specify the mass of the star and the initial configuration of its planetary system. $\endgroup$ – Rob Jeffries Oct 22 '15 at 14:36
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The Sun will not become a supernova, it will never explode. A star must have about 8 times more mass than the Sun in order to cause a supernova explosion. When it starts to fuse helium, the Sun will become a red giant and expand out to about Earth's orbit and throw out gas to form a beautiful so called planetary nebula. Mercury, Venus and maybe Earth will be inside of its photosphere when it is at the largest. I don't know if they will evaporate completely inside the thin hot gas of the red giant Sun.

The remaining planets will keep orbiting the white dwarf remnant, which is not a star (no fusion) but a compact planet sized object. It will shine like a star because of its stored heat. Orbits will change because the Sun will have only 40% of its mass left, the rest having been thrown out to form a nebula, over very long time. Orbits should become larger, and planets maybe will be pushed out a bit by the ejections from the red giant too. Gas planets maybe get their atmospheres a bit stripped off, icy dwarf planets like Ceres and Pluto could melt and evaporate a bit of their mass since the helium burning red giant is hotter than the Sun today. But I'm kind of guessing here, I don't know if those are significant effects.

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  • $\begingroup$ I think you should clarify the 40% more mass comment. For a white dwarf, that's true. Our sun will eventually turn into a white dwarf but before that happens it will lose a fair percentage of it's mass in it's final stages. A star probably needs (not sure precisely how much), but might need 2, maybe closer to 3 solar masses to have 1.4 solar masses remain in it's white dwarf stage. And, obviously, for type 2 super-nova, it needs at least 8 solar masses. $\endgroup$ – userLTK Oct 21 '15 at 9:46
  • $\begingroup$ I have reedited my question. My intention is that our system to be only an example. Thanks $\endgroup$ – CipherBot Oct 21 '15 at 11:39
  • $\begingroup$ Small point to add - I asked and got clarification. astronomy.stackexchange.com/questions/12205/… A sun in main sequence needs to be about 8 times more massive than our sun to eventually go Nova. A white dwarf, only 40% more massive but in the main sequence stage, about 8 times. Our sun is much too small. $\endgroup$ – userLTK Oct 21 '15 at 23:13
  • $\begingroup$ @userLTK That's no small point, I've always confused the maximum mass of a WD with the mass of a supernova progenitor. 8 times, that's why they are so rare. $\endgroup$ – LocalFluff Oct 22 '15 at 6:06
  • $\begingroup$ According to my calculations, if the mass of the sun is reduced to $\frac{1}{2}$ or less, the planets will all have escape velocity (In agreement with the answers here ). $\endgroup$ – Keith McClary Feb 13 at 4:44
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The short answer to your question is that the Sun's expansion will likely be insufficient to blow any planets out of orbit. It's possible that the Sun gradually losing mass could over long periods of time cause an outer planet to spiral out of orbit and become a rogue planet but that would be a gradual effect over a billion or more years, and, then, only maybe. No planets would be ejected from the rather rapid effect of the Sun expanding into a red giant.

Now, I think (I couldn't find a good link, will keep looking), but as our sun begins to burn Helium it will form a kind of stellar nebula. It won't be close to a supernova but it will cast off a fair bit of material and losing an outer planet or two during that stage might be possible - but far from a guarantee.

Would any of the 8 planets currently known, survive?

Mercury and Venus are not expected to survive the Sun going red giant but they would be eaten, not ejected. Earth is 50/50. (lots of articles on this, google "what will happen to the Earth when the sun goes red giant").

Now what happens to planets when a star goes SuperNova (which our sun won't as LocalFluff pointed out) - that's a good question. Some answers here: http://news.nationalgeographic.com/news/2011/08/110805-planets-survive-supernovas-ejected-rogues-space-science/ A supernova is likely capable of ejecting outer planets (and eating inner ones).

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  • $\begingroup$ I have reedited my question. My intention is that our system to be only an example. Thanks $\endgroup$ – CipherBot Oct 21 '15 at 11:38
  • $\begingroup$ You probably should checkout the national geographic article I linked above. Precise answers based on calculations would be too hard for me to even attempt, but in general, a supernova can eject outer planets, so loosely speaking, yes, but maybe just Neptune and possibly Uranus. The force to eject a gas giant planet might also strip away a lot of the planet's atmosphere. It might end up looking very different. $\endgroup$ – userLTK Oct 21 '15 at 11:58
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A supernova would vapourise all the planets in the stars planetary system.

There is a rule of thumb when estimating the effects of supernovae: however powerful you think they are, they are more powerful.

A supernova releases about $10^{44}$ joules in a matter of a few seconds

Now, a planet is a pretty small target, only about 1 billionth of the sun's heat hits a planet like (say) Jupiter, but 1 billionth of $10^{44}$ is still $10^{35}$ Joules. This is the same order of magnitude as the gravitational binding energy of Jupiter. In conclusion, a supernova has enough power to completely destroy Jupiter. It is possible that there might be a small core that survives, and would be ejected as part of the supernova remnant.

On the other hand, a smaller earth-like planet would be toast (although steam is a closer description, the planet would be vapourised.)

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    $\begingroup$ I think it depends also on the heat conductivity of the planet. The hot gases coming from the supernova are not particularly hot, maybe some tens of thousands K. Some seconds, minutes are probably not enough to vaporize the whole crust in my opinion. But many source states that planets will be vaporized. $\endgroup$ – peterh Feb 12 at 8:11
  • $\begingroup$ @peterh I would imagine the hot stuff coming out of the supernova has some extremely strong ablative power, capable of stripping off atmosphere, then crust, and so on, layer by layer. I guess it depends on density, speed, and temperature. $\endgroup$ – Florin Andrei Feb 12 at 8:26

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