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Is it possible for polar nights at one pole to be 8 & 1/2 months long without significantly messing up the climate?

The length of polar nights at the south pole from what i know is a week longer than the north due to the elliptical nature of earths orbit. What i am wondering is if it would be possible to have this week difference instead be a 2 & a half month difference, which is a lot more, without causing the climate of the planet to not be earth like. Aside from the longer polar nights it has 28 hour days and is significantly larger. Preferably through the same way of having a highly elliptical orbit but if that would always cause problems regarding climate some other way of making it happen is ok.

The main problem i see is that it would likely cause the southern hemisphere as a whole to be significantly colder warmer (i didn't think about it properly) which is something i want to avoid.

Is a significantly longer polar night possible without causing the planet to stop being earth like?

Edit: messed up meaning not able to sustain a climate similar to earth year round

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    $\begingroup$ Your plan will make the northern hemisphere colder, not the southern. At present Earth is closest to the sun in early January, and you’re proposing to make the difference more extreme but in the same direction. $\endgroup$
    – Mike Scott
    Jul 22, 2023 at 8:35
  • $\begingroup$ @MikeScott i am not very smart $\endgroup$
    – OT-64 SKOT
    Jul 22, 2023 at 9:10
  • $\begingroup$ It's grim up north $\endgroup$
    – smci
    Jul 23, 2023 at 7:48

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I think it depends on what you mean exactly by "Earth like" and "messed up". I suspect that a very large measure of messing up will occur as the only way to achieve what you want is to make the orbit of the planet a lot more eccentric so that it spends less time around its parent star and more time further away.

Even with Earth's very modest orbital eccentricity there have been times when most of the Earth was covered in ice due to "minor" fluctuations, so the prospect of a five fold increase in eccentricity does not sound healthy at all.

One problem will be the amount of light and heat reaching the planet. If you want the same average level of light and heat the planet will have to get very close to the star and get very hot to make up for the long time when it's away from the star.

If it's tolerable at closest approach it will be totally frozen at furthest reach and if it's tolerable at furthest reach it will be burnt to a crisp at closest approach.

No doubt some form of life could evolve, but I doubt it would be that similar to Earth.

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  • $\begingroup$ if there was something like a brown dwarf in the system could it be possible to have it work as an earth like planet? $\endgroup$
    – OT-64 SKOT
    Jul 22, 2023 at 9:08
  • $\begingroup$ A brown dwarf is basically a really big gas giant / really small star hybrid. But it won't help. It would be impossible for life to exist on its surface and if it was the central body it wouldn't help either because the problem remains that concerning near and far distances just closer in. $\endgroup$
    – Slarty
    Jul 22, 2023 at 13:54
  • $\begingroup$ i meant c ould one orbiting the main star somewhere else in the system to p rovide heat when it's further away from the main star h elp mrem $\endgroup$
    – OT-64 SKOT
    Jul 22, 2023 at 13:58
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    $\begingroup$ Perhaps it might to some extent, although I suspect the second star probably wouldn't always be in the right place at the right time. And if somehow it was, it would probably accentuate the eccentricity of the planet each year. Why do you need the polar region to have 8.5 months of arkness? $\endgroup$
    – Slarty
    Jul 22, 2023 at 14:26
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Without changing the orbits, you can also achieve the desired effects with a big mountain range more or less circling the southern pole. They will cast it in a shadow unless the sun is high enough.

Arctic shadow

The mountains need to be high enough to cover up as much of the sky, as the declination angle of the sun. You didn't specify the axial tilt of your planet or the year length, so I'll calculate those for Earth values; see here for the formula to get it with different values: https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle

You want two-and-a-half month longer nights, so one-and-a-quarter more on each side. The declination of the sun at 41 days past the March 22 equinox, May 2, is 15 degrees.

The angle of an object in the distance is calculated with a = 2 * arctan(g / (2 * r)), where g is the object size and r the distance (in the same unit of length). Resolving for a = 15° with a reasonable mountain height of 5 km yields 19 km. So you can cover up the pole and a circle with a radius of 19 km around it. That's about the size of Paris.

More ambitious 8km mountains let you cast a circle with a radius of 30 km in shadows. That just about covers Greater London, or most of Luxembourg.

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