"Nightfall" by Isaac Asimov (you can hear the story here on escapepod, if you need it) postulates a planet in a multi-sun system. The orbital mechanics of the 6 suns result in all of the sides of the planet being illuminated all of the time but for one short period of a single 'day', at the 5 big suns just happen to align on one side of the planet with the dimmest one blackened out by the single moon opposite to them, leaving it to rotate a full time with a considerable (half) of the planet not illuminated. This event happens all ca. 2050 years, resulting in massive fear of the dark and crumbling society.

Now... How would this Hexa-star system have to be set up, assuming there is no other planet or moon?

  • 4
    $\begingroup$ This paper seems to describe what you want: arxiv.org/ftp/arxiv/papers/1407/1407.4895.pdf I'm not going to turn that into an answer since I'd be copy-pasting what's in the paper into an answer. $\endgroup$ – Green Jun 13 '18 at 13:09
  • $\begingroup$ @Green sadly, it does only describe a short stable period, as evident in the drifting apart of the two suns, and no check was done if the period of 2049 years was kept... but a good read nontheless (and oddly enough also the one that was linked to in the very short lived link only answer) $\endgroup$ – Trish Jun 13 '18 at 13:15
  • 1
    $\begingroup$ @Trish everything I read about complicated solar systems like this is that they aren't ever stable over geological time scales. There's just too much sensitivity to initial conditions that add up over time. $\endgroup$ – Green Jun 13 '18 at 14:04
  • $\begingroup$ I added the PDF because I believe it answers your question and not everyone can see deleted answers. $\endgroup$ – Green Jun 13 '18 at 14:04

Designing a star system that has a planet with perpetual sunlight for thousands of years at a time is an almost impossible problem. Therefore I would say:

This looks like a job for Sean Raymond of the PlanetPlanet website:

And in fact he has discussed the many, many problems with designing a Kalgash system that will work as in the story, in some posts this year.



Sean decided that the Kalgash system as described in the novel wouldn't provide the necessary length of time between darkness.

so he designed a different type of solar system than in the story and novel, in order to get one where a planet could have eternal light.

And I suppose that his answers are the best you can expect to get.

| improve this answer | |
  • $\begingroup$ Thanks for the plug! And I'm happy to answer any questions about the systems I set up if anyone is interested. $\endgroup$ – Sean Raymond Jun 14 '18 at 7:40
  • $\begingroup$ you might also pick up Green's comment to add this PDF with a short resumee, because together with Sean's texts, it illuminates that Klgash might be possible as a Hexa-star system with 2 doubles and 2 singles and two planets around the single, but possibly not on the time between nightfalls as described in the story. $\endgroup$ – Trish Jun 14 '18 at 8:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.