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There is a planet orbiting a binary system inside the Goldilocks zone. The problem is that the binary system is of a violent kind. It either regularly explodes and sterilizes a portion of the planet's surface (recurrent nova) or constantly bombards the planet with X-rays (X-ray binary).
Can carbon-based life survive in these conditions?

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    $\begingroup$ Do you want to know about basic, monocellular life or more evolved one? $\endgroup$ Jul 12, 2022 at 11:58
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    $\begingroup$ The evolved one, please. $\endgroup$ Jul 12, 2022 at 12:04
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    $\begingroup$ It's a little like the "The Three-Body Problem" written by Liu Cixin. Through I don't know about scientific basics, you may find some relative ideas in this book $\endgroup$ Jul 12, 2022 at 12:35
  • $\begingroup$ @Anton Lioznov "The Three-Body Problem" is about a planet with an upredictable orbit that often leaves the Goldilocks zone, its not related to the question. $\endgroup$ Jul 12, 2022 at 13:10
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    $\begingroup$ The recurrent nova link provided suggests an increase in output for the star averaging ten millionfold. The minimum example there was 1.5 million times the output. Using earth as an example, the average square metre receives 21.6 MJ per day. So it would receive 30 TJ/day. At that point, we need to switch to nuclear weapon equivalents - that's 0.24kT per square metre, for the duration of the nova. At the very least, the seas would boil to their bottoms and the land would be scythed to bedrock. This seems impossible for life to survive. $\endgroup$
    – jdunlop
    Jul 12, 2022 at 21:14

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It needs to be calmer

You said yourself that the novas regularly sterilize part of the planet (I assume the suns-facing side). Unless this event occurs very infrequently (like, once per tens of millions of years), you will not have any life on the planet.

For life to exist, it needs an environment it can survive in long enough to reproduce and evolve. If single-celled organisms happen to appear, they will have to be lucky enough to not get blasted for the millions of years it takes them to spread around the planet, or else one nova can be a 100% extinction event.

Even if they make it past that point, regularly Thanos-ing the planet will make it very, very difficult for any form of intelligent life to develop, civilize, and advance. This further highlights the requirement for such an event to be extremely rare. Life on Earth, let alone Humanity, would never be able to get to this point if half of the Earth got set back to 4 billion B.C.E every thousand years. And this isn't even acknowledging the constant X-Ray bath, which would be constantly turning genetic code to Swiss cheese and giving everything cancer.

EDIT: As @jdunlop pointed out, recurrent novas are not an instant burst that would sterilize half the planet, but are in fact a sustained brightness increase of, according to your Wikipedia article, 8.6 magnitudes (400,000,000x), for days or weeks. So, all life, not half of all life, would be sterilized. This means your proposed planet is not almost uninhabitable, it is entirely uninhabitable. Every time this happens the planet's surface would melt and maybe vaporize.

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    $\begingroup$ Nice use of "Thanos" as a verb, though this is actually worse than Thanos, because rather than all of the disappeared being randomly distributed amongst the population, it's literally every living thing (and probably most structures) on one entire hemisphere. Anything resembling a civilization would be impossible under those conditions. $\endgroup$ Jul 12, 2022 at 21:00
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    $\begingroup$ Not the sun-facing side - per the recurrent novae link provided by the OP, the star flares its output by a factor of about ten million - and keeps doing so for weeks. This would annihilate everything on the planet (if not the planet itself). $\endgroup$
    – jdunlop
    Jul 12, 2022 at 21:09
  • $\begingroup$ @jdunlop This is a good point, I will update my answer. $\endgroup$ Jul 13, 2022 at 16:07
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Maybe.

If life evolved under those recurring conditions, it is possible that it can adapt to them, in the same way some life forms have adapted to thrive when exposed to oxygen, which is otherwise toxic for others.

Even on our planet we keep finding life forms where we would not expect them to be, so we cannot exclude that what we deem unfit for life actually is totally fit for a life adapted to it.

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    $\begingroup$ You make a point, but I wonder how often those explosions occur? Every century and I can't suspend my disbelief enough (can a single-cell life form evolve a resistance to hemisphere-sterilizing radiation?). Even every millennium stretches my credulity... but every million years? Now I can believe life would form. But now we're Chicxulub-meteor rare. I'm having trouble buying into becoming resistant to an ELE. The explosions would have to be at just the right frequency with a hounding good amount of luck. $\endgroup$
    – JBH
    Jul 12, 2022 at 14:15
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    $\begingroup$ @JBH, at the century level, that's plenty of time for life (or proto-life) to migrate from the unharmed side of the planet. Even the slowest oceanic circulation on Earth (the North Atlantic Deep Water traveling around South America to rise in the north Pacific) only takes a thousand years; the surface currents move much faster. (And thousands of meters of water makes for an incredibly good radiation shield -- expect early life to evolve in the depths, then migrate to the shallows as it gains radiation resistance.) $\endgroup$
    – Mark
    Jul 13, 2022 at 1:59
  • $\begingroup$ @Mark I understand your point... I'm simply not convinced that wiping out 50% of life, which will happen on different parts of the planet over time, will permit any meaningful evolution. $\endgroup$
    – JBH
    Jul 13, 2022 at 15:50
  • $\begingroup$ @Mark Recurrent nova, it turns out, are not single-moment burst events, they last for days. In other words, it doesn't wipe half the planet, it wipes the entire planet. $\endgroup$ Jul 13, 2022 at 16:15
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Hydrothermal Vents

Complex life exists in the deep sea. Half a dozen miles of salt water should provide insulation from the radiation storms. To quote my earlier answer:


There are already ecosystems on Earth that are separated from the sun. For example tube worms feed off the energy released by hydrothermal vents.

enter image description here

Of course a tube worm cannot snatch a human out of its shoes. But it's not just tubeworms down here. Look closer -- there is a ghost crab and some small orange Pokemon hiding in there.

enter image description here

Your Night Land Monsters have as the bottom of their food chain something akin to smokers. I leave it to your imagination how the smokers got so close to the surface that the denizens ever encounter humans.

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Deep life

I am thinking of earth before the ozone layer formed. It was a rough place topside. Down by the black smokers in the deep ocean it was comparatively placid. Less hard radiation, water to moderate the temperature, a steady supply of tasty sulfur and iron carried up from the energetic depths by the water cycle. It was not until things really got started in the ocean and ozone could block the UV that Earth life could get going on dry land.

Minerals are good protection against radiation. In your world the crust plays the role that the oceans did on earth. Deep in your inhospitable world, life is sheltered from the hard rays. Life forms are treated to tasty energy-rich molecules generated on the surface by the radiation and transported to the depths by the water cycle.

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Life can survive using a couple of methods of coping with increased radiation. First off, radioresistance varies across organisms and can be quite high. Look at some of the pictures of how the wildlife around Chernobyl has rebounded despite the radiation. Since radiation causes cellular damage, repairing the damage quickly is one such method of how an organism can adapt to handle higher radiation amounts. Another method would be the evolution of shielding. Lifeforms inside thick exoskeletons are potentially less likely to be effected by external radiation. Molting after being hit by radiation could allow organisms to avoid most of the negative effects. A combination of these two factors could easily give you organisms capable of thriving in such an environment.

One issue such a planet would face is the rate of exposure. Too long between exposures can be just as bad as too short. But a short time between radiation pulses is only an issue for lifeforms which have not adapted over time to resist it. In order to adapt to radiation, organisms must be exposed to it often enough to kill off the less resistant offspring and allow the more resistant offspring to procreate, but if the periods between exposure events are too long, less resistant organisms will thrive and weaken the genetics of a species. If such exposure is predictably cyclical, then organisms could hibernate underground during the radiation storms.

If we have the initial organisms on your planet evolve in the deep oceans, then over time those which adapt a slightly higher radioresistance will move into shallower water. Higher radiation means more mutations, until organisms develop genetics, or biological defenses, capable of resisting harmful mutations. The process continues, with organisms adapting to enable their expansion into previously inaccessible niches. Perhaps one of these organisms evolves a thick shell to protect itself and is the mother to a new evolutionary line which branches into thousands of new species. Maybe plants evolve extra bark or a thick canopy which is rapidly replaced after a large radiation dose. Look at how plants have evolved to deal with wildfires as an example.

As long as the ancestor organisms evolve a resistance to high radiation, that trait can be passed on to their offspring. Wait a few billion years and you will have a world full of organisms perfectly adapted for their radiation soaked environment. An environment deadly to a human being could just be another day in the life for your planet’s natives.

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Mutant Tardigrades

Extremophile life is real. If life evolved in that planet, it most probably is extremophile organisms, who are able to enter a cyst state to survive the extreme heat and whose bodies aren't suceptible to x-ray radiation.

Earth's Tardigrades already to this:

Tardigrades Can Survive X-Ray Bombardment by Deploying a Protein Shield (ref)

A study in 2016 discovered that a protein unique to tardigrades called Dsup (damage suppressor) could suppress X-ray-induced DNA damage in human cells by approximately 40 percent.

As for the sterelizing heat, picture ants walking inside a working microwave oven without getting cooked. They are too small to properly capture and keep the heat.

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So, you have the surface constantly bathed in x-rays, and the surface is regularly obliterated by its star.

First off, the planet is constantly bombarded by x-ray radiation. I think this is the lesser problem, as with the right adaptions, life could thrive in the high radiation environment, although the life would probably have to originate underground and evolve the x-ray resistance later. How about these organisms have exoskeletons to shield themselves from radiation, or how about there is lots of lead on the planet, which the animals could use to cover themselves, a biological lead apron. The plants could even use the x-ray radiation to their advantage, maybe they can harness the x-rays to use along side light energy. There are many possibilities.

Now, the bigger problem(in my eyes) is that the planets surface is wiped clean every couple years. Now assuming the whole surface is wiped out, and not just one hemisphere, and lets assume the pessimistic, that it happens every 2 years(the most frequent ones happen every 1 year). How about some sort of hibernation. Some animals on earth hibernate during the winter months and emerge in the summer. Animals on this planet could go deep down, hibernate, and reemerge when the nova is done. The plants meanwhile could maybe have very deep roots and embed seed pods underground, which could sprout back up after the nova along with the animals. Or maybe they have some completely different way of surviving through the apocalypses that happens every couple of years. Again, many possibilities.

All in all, I think carbon-based life seems probable on this planet, although it would need the right adaptations.

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Yes, up to a point.

Water is good protection. It has high heat capacity and blocks much hard radiation. Because it has a maximum density at 4C and because ice floats on water, it takes a very long time for surface heat to reach the depths. Many miles of deep if you need it.

Life evolved in the oceans. The Chixulub impact didn't have nearly such catastrophic impact on marine life as it did on terrestrial life.

So, because of more frequent catastrophic upheavals, life on this world never loses its ability to survive deep in the oceans. When it gets too cold, or too hot, or too "hot" with radiation, everything dives into the ocean and swims down out of harm's way while the terrestrial environment gets a big reset. Depending on timescales, life may need to go into deep hibernation down there. Life will have evolved senses to sense the approach of the hot or cold, and the easing of such that will allow emergence from hibernation.

The situation of the "spiders" in Vernor Vinge's A Deepness in the Sky is almost exactly like this. Their star regularly flares and gives the terrestrial environment a brief hurricane of steam, then slowly cools down, and down, and down, until they have to hibernate deep underground for ~200 years until the next flare. (Reasons = Spoilers). Oh, and they've acquired a technological civilisation, and they're starting to think about breaking with the natural cycles which nature and evolution imposed on them.

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