# Thread: How would a 70+ year long night be possible?

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## How would a 70+ year long night be possible?

Dear forum,

I'm a musician interested in astronomy and physics and all, but I have very little scientific background up to date in those fields, so I come here for a little help.

A fiction I wrote, called "The Night" involves a night that is at least 70 years long, and while the planet's inhabitants believes it is some kind of apocalypse, end of time, or God's will, I wanted to find a solid background where such night, while not being frequent, could happen.

First, I thought that a planet orbiting a brown dwarf, itself orbiting a main-sequence star, could experience periods of "more than total" eclipse and be in the umbra of the brown dwarf for some time. In order to last 70 years, though, the orbital period of the planet would have to be insanely great, so I thought it'd be implausible.

Then I came across some info about Epsilon Indi A, who is orbited by E Indi Ba, a brown dwarf, which is orbited by another brown dwarf, E Indi Bb. The problem is that E Indi A is a red dwarf, and E Indi Ba is at 1500 AU of it, and that means that if a planet orbits E Indi Bb (which is at approximately 2 AU of Ba), it would receive so little light (and heat!) from the main star that it would be night almost all year long, even if the radiative heat from the two brown dwarves might make some life possible. The planet needs to experience day in order to have night, too. So that system's out.

And I thought that a similar system, albeit around a larger star (maybe G or F), and closer than the 1500 AU of E Indi Ba. Even if the orbital period of a planet surrounding the analog to Bb would not be insanely long, it would be possible to experience longer than habitual nights in special circumstances.

Could we also include super Jupiters, closer to the main star that could also eclipse it from the point of view of the planet, in order to extend the "night" to an ultimate degree, where such circumstances occur only once in a billion years, let's say.

Can anyone help me a little?

Thanks a lot!

2. If you had an Earth-like planet that was actually a quasi-Moon of a Super-Jupiter planet, orbiting an M4 red dwarf in an appropriate orbit for getting a good temperature, you could have that planet be lissajousing around the L2 point, sometimes above the shadow, and sometimes below it, but every once in a while perturbed to be right in the middle for an extended time by interaction with some other object (say a planet in a horseshoe orbit).

I want to be clear that this is *very* unlikely since the L2 point is not a stable L2 point. More likely, this planet would simply escape and orbit separately.

3. About the only ways I can think of are a) a very bright primary, where the planet has either a very great axial tilt or is only habitable in the polar regions -- this implies a 140 year orbital period. b) a very slow reverse rotation.

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Thanks, but as you said the L2 point would not be stable enough to harbor life, and the way you put it, the long periods of darkness would be common, which should not be.

Also, swampyankee, I'm talking about a planet-wide night, sadly it's not only an axial tilt thing or about the rotation speed, but thanks for collaborating.

5. Sounds very much like Uranus.

6. At least 70?
How about a tidal lock, or on the way to being one?

7. Originally Posted by Xibalba
Thanks, but as you said the L2 point would not be stable enough to harbor life, and the way you put it, the long periods of darkness would be common, which should not be....
I didn't say not stable enough to harbor life, I meant not stable enough to stay put...
Let's try this similar idea: Imagine a livable planet in the horseshoe orbit with the Super-Jupiter, and some interaction with a Moon drops this planet into L2, where it stays for your 70 years... until L2's natural instability sets it free again.

8. Originally Posted by a1call
At least 70?
How about a tidal lock, or on the way to being one?

The 70 year bit makes that tougher.

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Sorry guys, I've thought about what you suggest and it doesn'T work. The planet needs to have a normal day-night cycle, and be habitable for carbon-based life and superior animals like humans. The other problem is that this 70 years night mustn't be a common thing, and it cannot be irreversible, either, that puts out the idea of tidal locking.

The only way I've figured out is if the planet was passing behind a great celestial body, let's say a gas giant. If the planet orbits said giant, then it'd be common to pass into it's umbra, a phenomenon lasting a few hours to a couple days, maybe?, but if this brown dwarf orbits a much larger brown dwarf, on a quite large (maybe elliptical?) orbit, it'd be possible that the planet is inside the umbra of the gas giant or the brown dwarf long enough. ???

I also thought that the planet could orbit a brown dwarf, quite cool (but which emits enough heat to make life possible on the planet), the brown dwarf itself orbiting another star, like a O or A class star at a huge distance so that from the planet's point of view the star is as big as the sun in the sky, approximately, but blue-ish. (then what color would be an earthlike atmosphere under those rays?) Then, a sort of cataclysm could happen, like the star imploding, or an errant planet passing by, or anything else you can think of??

10. There are numerous ways to make a 70 year night, but it's a challenge to make it occasional. The short answer to your question is that it's impossible.

By the way, is this "night" supposed to affect the entire planet? Normally, "night" only affects half of the planet. (Actually, a little less than half.)

11. I would think that to change the length of a night...to 70 years..

and then re instate the previous period of night..

Impossible..

and hay, ! people, why all the twittering on about orbital periods around multiple stars and planets... Bla, bla, bla...

Its the planet rotation about it's own axis that determines day length..

How or what is going to stop a planet rotating for 70 years... ? or What could get in the way for 70 years...

NO. just, no.

12. OR could the star be interrupted without other damage ?

Could the Solar system pass through a defuse dust cloud ?

effectively shielding the stars energy flow.. for 70 years... umm.. maybe, but still, No.

13. I see no way to make such a thing periodic and survivable. Perhaps a wonky resonance with a planet in a highly elliptical orbit could lead to the two occasionally swapping orbits (there's a much less extreme case of this in our solar system, Epimetheus and Janus), but if the event were survivable, the planet would still experience a day/night cycle with a dimmer sun, it'd just get cold.

The best I can come up with is a collision of planets in close orbit around the sun producing a debris belt that obscures visible light, but lets enough infrared through to keep the planet from completely freezing. The collision would need to be rather more catastrophic than the one thought to have created the moon, but the higher collision velocities (especially with a rogue object on a hyperbolic trajectory passing close to the sun) and stronger tidal effects from the sun might help out here. It'd take a lot of dust to block out the sun completely, and I'm not sure anyone would describe the effect as "night"...streams of dust progressively covering the sun over a period of weeks or months, then thinning to a ring crossing it over the following years, rather than suddenly going dark and then clearing at some point. And it'd only reasonably happen once.

14. Wasn't this more or less the plot to Asimov's "Nightfall?" Although IIRC correctly, night came every few centuries on that planet.

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Originally Posted by Daffy
Wasn't this more or less the plot to Asimov's "Nightfall?" Although IIRC correctly, night came every few centuries on that planet.
It also only lasted about the normal length of time. That world didnt have a day-night cycle, just different positions of its 5 (6?) stars.

As for the OP... What about another planet closer to the primary whose orbit is exactly the same as the one experiencing night. The interior world is also on a very slowly wobbling plane so that for 70 years it wobbles in an out of obstruction. This very slow wobble back and forth could equal out to the length of time between obstruction you need for your story.

Is any of it even possible? Idk, but as this is fiction I say take some liberty with physics.

16. Originally Posted by ZunarJ5
It also only lasted about the normal length of time. That world didnt have a day-night cycle, just different positions of its 5 (6?) stars.

As for the OP... What about another planet closer to the primary whose orbit is exactly the same as the one experiencing night. The interior world is also on a very slowly wobbling plane so that for 70 years it wobbles in an out of obstruction. This very slow wobble back and forth could equal out to the length of time between obstruction you need for your story.

Is any of it even possible? Idk, but as this is fiction I say take some liberty with physics.
The problem is if there is another planet blocking the sun then that planet is closer to the sun and being closer to the sun it would need to have a shorter orbital period meaning they couldn't stay in alignment not to even think about the size that planet would need to be in to eclipse the sun for the whole planet.

Make some huge object built by some ancient civilization the culprit. Nothing natural is going to cause this effect.

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Would it be possible that a rogue object, maybe a planetoid or even a planet comes by and is captured by the main planet at Lagrangian point L1... I don't know if this point is really stable, but would it be possible that it stays around this point so it occults the sun for an extended period of time? It is possible that the occulted planet's orbit vary a little, although still much within the habitable zone of the star?

We're talking about a 1 in a googleplex event here, so be creative.

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What if the entire solar system passes through an interstellar dust cloud or some other sparse, cold body of matter that blocked all or most of the sun's light? That would make it a 1-time event.

19. Originally Posted by Xibalba
Would it be possible that a rogue object, maybe a planetoid or even a planet comes by and is captured by the main planet at Lagrangian point L1... I don't know if this point is really stable, but would it be possible that it stays around this point so it occults the sun for an extended period of time? It is possible that the occulted planet's orbit vary a little, although still much within the habitable zone of the star?

We're talking about a 1 in a googleplex event here, so be creative.
This is pretty similar to what I described in Post #7 above, which I still think is your most likely scenario, but you've rejected for some reason.

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Well the goal is to make it survivable. Maybe it should be a more planet-side phenomena. An unusual event kicks up a massive dust cloud into the upper atmosphere/low orbit that blocks visible light but perhaps re-radiates the energy into wavelengths that can keep the planet warm... enough?

21. Originally Posted by JCoyote
Well the goal is to make it survivable. Maybe it should be a more planet-side phenomena. An unusual event kicks up a massive dust cloud into the upper atmosphere/low orbit that blocks visible light but perhaps re-radiates the energy into wavelengths that can keep the planet warm... enough?
You'd need less dust than the cloud around the star, and thus a less catastrophic event to cause it, but you also need the dust-forming event to be a lot closer to the planet. A collision splattering a good chunk of the moon into orbiting dust would also shower Earth with debris. An impact on Earth that kicks enough dust into the atmosphere to completely block out the sun planet-wide would probably not leave witnesses. Also, both of these would more dramatically cool the planet. A dense cloud of dust closer to the sun would at least heat up and radiate a decent amount of heat, maybe enough to keep some liquid water around (small bright disk versus huge fuzzy reddish cloud).

A planet-encircling dust cloud would also have to be a lot denser to be opaque, and would more easily eliminate nights (by reflecting light back at the planet...think of Saturn's night side lit up by its rings) than the day. And either way, it wouldn't fade abruptly after 70 years. The once-every-2049-years night of Nightfall required quite a contrived setup, but a 70 year planet-wide night...

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I know it's tricky here. I mean, really! But there are oddities out there, of which our own solar system may belong to. I didn't read Asimov's Nightfall, but it seems like I will have to.

A planet-wide dust cloud wouldn't appear and disappear quickly enough, and it'd have its lot of bad consequences on the planet's weather and life. Same thing for a ring of dust around the star. Of course it'd be a really cool and easy way to solve the problem, but it's just not plausible.

Keep in mind that the structure of the stellar system and the arrangement of the planets, and if it's a binary or more system, if there is brown dwarves, what is the class of the star.... nothing is down yet so you can go wild about your thoughts.

I'm running, too, but all I find doesn't nearly make it.

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Originally Posted by Xibalba
A planet-wide dust cloud wouldn't appear and disappear quickly enough, and it'd have its lot of bad consequences on the planet's weather and life. Same thing for a ring of dust around the star. Of course it'd be a really cool and easy way to solve the problem, but it's just not plausible.
A planet wide night lasting decades will have lots of bad consequences for the planet's weather and life no matter what the cause. Ignoring the weather for the moment the simple lack of light will rapidly cause a more or less total ecological collapse by killing off all plant life making the bottom drop out of the food chain leading to everything starving to death other than any groups that are able to grow crops under artificial light and the few ecosystems that aren't based of photosynthesis (primarily found in the deep oceans around hydrothermal vents or hydrocarbon seeps).

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25. Wouldn't it be easier if everyone just went blind for 70 years?

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Artificial satellites can be in a solar sychronous polar orbit around Earth, but minor station keeping is required for them to stay in eternal sun light or shaded by Earth for 70 years. Perhaps an earth like planet can do a simular 4 hour orbit around a brown dwarf that has cooled to about 300 degrees c and thus is suppling only infrared light to the planet. The brown dwarf orbits binary G type suns which produces contious day for about 100 years during the enternal day portion, then 70 years of the eternal night portion. Problems are the planet, might disintigrate because it is inside the roache limit of the brown dwarf, tides would be huge, would tide lock to the brown dwarf, likely in less than one million years, three heat sources during the middle of the eternal day portion. Only the brown dwarf would be a heat source during the eternal night, so it would be at least a little colder. Also there would be perhaps a month of twilight at the beginning and end of eternal night, and the solar sychonous polar orbit is a bit unstable. The instability might be a plus as something might shorten the evening twilight by perturbing the solar sychonous polar orbit. The brown dwarf could orbit eliptically 3.8 to 4 AU from the from the binary G class stars, thus fine tuning the results of this one time or rare event and thus providing a reasonable light level, but not much heat from the binary G stars. All these events occuring at the optimum time are low probability, but not zero probability. Please correct, refute and/or embellish. Neil
Last edited by neilzero; 2012-Feb-04 at 03:27 AM.

27. I'm not seeing how a 4 hour sun-synchronous polar orbit around a brown dwarf is ever supposed to produce a 70 year eclipse, having a binary pair of bright suns only makes the situation worse. Such an orbit will either never have an eclipse or would have short eclipses every 4 hours. An imperfect solar synchronous orbit might allow a 70 year period of an eclipse every 4 hours, but that's not going to be a 70 year night.

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Yes, creating a plausible scenario where a 70-year long planet-wise night, and making it a one-in-a-lifetime event, is incredibly hard mentally.

Wouldn't it be easier if everyone just went blind for 70 years?
Yes, but no; night does not equal blindness.

Would it be possible that the sun experience a global sunspot, or that it is so active that the number of spots at the surface of the star decreases it's luminosity? I know knowledge about star's mechanisms isn't really complete yet, but I think it would be plausible that in a star's lifetime, there is one period of time where the activity of a cycle is so intense that it covers its surface almost entirely with sunspots???

29. Originally Posted by Xibalba
Yes, creating a plausible scenario where a 70-year long planet-wise night, and making it a one-in-a-lifetime event, is incredibly hard mentally.
It's not at all hard to make a 70 year planet-wide night a once-in-a-lifetime event. No matter how long the natives normally live, a 70 year night is likely to kill almost everyone pretty early on, making it rather difficult to witness two such events. But other than that, it's just hard to make a 70 year global night, period.

You've got to eclipse the sun somehow. The orbital mechanics involved make such a long eclipse by another planet basically impossible. You need the eclipsing object to encircle the sun or the planet, which pretty much leaves you with obscuring the sun with lots of dust, and any such violent dust-producing events involving the planet are likely to be fatal to anyone who would otherwise witness the night. Smashing up a close orbiting planet might do it, but it won't start or end quickly. The scenario of a sudden global 70 year night that ends quickly and completely just looks impossible as a natural occurrence.

It might be doable as an unnatural occurrence, but why would someone go to the trouble of blocking the sun from a planet for 70 years, and then just stop?

Originally Posted by Xibalba
Would it be possible that the sun experience a global sunspot, or that it is so active that the number of spots at the surface of the star decreases it's luminosity? I know knowledge about star's mechanisms isn't really complete yet, but I think it would be plausible that in a star's lifetime, there is one period of time where the activity of a cycle is so intense that it covers its surface almost entirely with sunspots???
That would only dim it, and nowhere near enough to make it appear to be nighttime. The sun illuminates Earth with over a kilowatt of light per square meter. It takes only a few watts to illuminate the same area at comfortable levels, lighting in a well-lit room is nowhere near as bright as sunlight. Even if the sun was only a thousandth as bright, there'd be a clear difference between night and day. (For reference, the full moon is about 1/400000th as bright as the sun. The illumination in the situation above would be 400 times as bright as under the full moon.)

Not even the most variable stars vary nearly enough for this to work. Vernor Vinge invented a bizarrely variable star in A Deepness in the Sky (known as the On/Off Star in-story), but no such stars have been discovered and there's no reason to think they're possible (the inexplicable behavior of the star was one plot point in the book).

30. What if a probe from a machine civilisation entered the star system, decided it needed to do some solar energy harvesting without concern for the inhabitants of any nearby worlds, and set up a vast sunshade at the habitable planet's L1 point (the point between the planet and the star) that completely eclipsed the star or absorbed over 99% of of its light? Then after 70 years, it's absorbed enough energy to do what it needed to do, and it moves on.

Being artificial, it can maintain its position (using thrusters or whatever) at the L1 point for that duration, and you don't need to invoke weird orbits or superjovians either.

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