(first post from a writer drafting a sci-fi novel, so please forgive any ignorance or missteps and TIA!)

Let's say Alpha Centauri Cb is habitable, under these conditions:

  • Air quality capable of sustaining human life, but only 14% oxygen

  • Gravity is 10% more than Earth

  • Robust atmosphere; however does not fully shield from cosmic storms (solar flares etc.)

  • Dwarf red star (Proxima Centauri) has only 70% of Earth's sun power, which allows for necessary infrared (heat) light but not lethal UV levels

  • A powerfully strong magnetic field (separate question to follow)

  • An 11-day orbit, with each day/night period lasting 59.86 Earth hours; roughly 30 hours' daylight, followed by 30 hours' darkness

  • An aside, in case any are curious about how I might propose a work/life schedule for a 60-hour day:

    • Light

      • 0-5 hours work
      • 5-6 hours lunch
      • 6-10 hours work
      • 10-11 dinner
      • 12–15 hours play
      • 15-24 hours sleep
      • 24-30 hours work
    • Dark

      • 30-31 lunch
      • 31-36 work
      • 36-37 dinner
      • 37-42 play/sleep
      • 42-43 secondses
      • 43-48 work
      • 48-49 last supper
      • 49-60 rest/sleep

My story plot requires an "expected" period of increased cosmic activity (a summer solstice of sorts), and also a colder, darker period (winter). These seasons would obviously affect the work/play life balance, and factor into the plot. Planet tilt, or other more physics-related necessities, are beyond my scope of figuring. Given these parameters...

Does it work to assume an 11-day orbit would experience a progression of these seasons, much like a year in Earth's Northern Hemisphere? What kind of weather might occur within such rapidly progressing seasons?

Tangential suppositions/requirements:

  • I cannot permit Alpha Centauri Cb to be tidally locked to Proxima Centauri, otherwise I fear the living conditions would be too permanently bright and hot for human flourishing.
  • And yet, if Cb is not tidally locked, then I reach my limit in visualizing how its rotation and orbit around Proxima Centauri will produce what kind of seasons.
  • Geographically, my plot requires one large fertile, habitable valley, with the rest of the planet rather stark and primitive, with frozen seas and massive glaciers rich in precious resources. Some inhabitants have settled in the valley, while a few others conduct remote "off-road" trips for mining, exploration, etc.

(I would not be at all surprised if some of my conditions proved contradictory, as my brain has considerable computational limits in the realms of science.)

  • $\begingroup$ As an alternative, you can also delete this question and post it to our Sandbox which would give people the opportunity to help you with question writing skills. $\endgroup$
    – elemtilas
    Dec 14, 2023 at 21:05
  • 1
    $\begingroup$ Thank you @elemtilas! I will split into two. Not sure what VTC is, but hoping you'll see when I've edited it. TY again. $\endgroup$ Dec 14, 2023 at 21:50
  • $\begingroup$ VTC means Vote to Close. Questions that don't meet the site's criteria are put on hold while edits are made to resolve the reason for closure. There's a similar review and voting process for reopening closed questions. This site functions differently from forums, or other Q&A sites. You can read more about how the site works by visiting the help center or taking the tour for a quick overview. $\endgroup$
    – sphennings
    Dec 14, 2023 at 22:06
  • 1
    $\begingroup$ Hello! Your question looks much better now! I'm going to withdraw my Vote to Close as you have (very timely!) fixed the issue. Please feel free to ask other questions about your world --- focused on a single problem like this one now is. Also, please link any subsequent questions back to this one so people can get a better understanding of your world! $\endgroup$
    – elemtilas
    Dec 14, 2023 at 23:57
  • 2
    $\begingroup$ Wonderful, thank you so much @elemtilas! Will make sure I link subsequent questions back to this one. $\endgroup$ Dec 15, 2023 at 3:06

1 Answer 1


You’re spot-on with the 60-hour day. Note that this is a little under two days per orbit - the planet’s orbital period is a little over 11 Earth days.

So, to answer, a 60-hour day would certainly produce seasons, with one season happening one day and the other season happening the other days (on a 50/50 alternation). This can be justified in a cool way:

The planet’s orbit is a little more eccentric than Earth’s.

What this means is that it gets closer to the star at one end of its orbit and farther away at the other. The eccentricity doesn’t have to be high; the orbit might appear circular at a distance, but a difference between highest-point and lowest-point of a few thousand kilometers makes some days hotter than others. Paired with a tilt on the planet, this makes some areas hotter (because they’re more exposed in the “summer” season and less exposed in the “winter” season) and some areas colder (because they’re more exposed in the “winter” season and less exposed in the “summer” season).

Right in between you’ll find a happy little medium, where there’s a valley that has just the right temperature and atmospheric characteristics and that goes through a balanced summer/winter cycle, whereas the other regions will be either baking hot all the time because they don’t experience winter or freezing cold (glaciers with useful minerals!) because they don’t experience summer.

What kind of weather might this one-day-summer, one-day-winter produce? Well, first off, if there’s a lot of water on the planet (perhaps by terraforming, or maybe it was there naturally), there would be alternating snow and rain: water would be quickly evaporated in the summer and then, the next day, it would rain back down in the cooler winter temperatures (or snow in the colder regions). Floods might be an issue if there’s too much water on the planet, and in the more extreme latitudes, extreme snowfall might be an issue too. Imagine having to snowplow a solid quarter of the planet every other day!

All in all, the eccentricity of the planet’s orbit adds quite a bit of flavor to the weather, and provides the nice summer/winter cycle that is present in the habitable regions of the planet.

  • $\begingroup$ TY very much for your detailed answer. You've made sense of what I was struggling to picture in my head. I will edit my question above, as I think the math works a bit better if Alpha Centauri Cb orbits Proxima Centauri in 10 Earth days: that is, ~240 hours, which would mean Alpha Centauri makes 1 orbit, 1 "year" only four 60-hour day/night periods! That's pretty handy, to have: Day 1 = spring Day 2 = summer Day 3 = fall Day 4 = winter, and repeat. $\endgroup$ Feb 3 at 17:43

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