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The planet has 256 days in a year, split up into eight months, each with 32 days.

My planet is a bit smaller than Earth: Think, enough space for the continents of Earth’s western hemisphere and the Pacific Ocean, only the continents are split up a bit and there are islands scattered across the other side of the planet, where there would otherwise be only water. I’m hoping to avoid any extreme world-wide climate effects on account of star type and orbital period, because I’d like for the climates across the world to be fairly Earth-like in variation.

What star type would be ideal for this planet based on the length of its year that would also give it a climate comparable to Earth’s? Could the hours in a day be the same (For instance, would midnight still be the twelfth hour?) Would there be any slight or glaring effect on climate or atmosphere? And what would this star look like in the sky? Would its journey from one horizon to another be different?

Ideally, I’d like for the differences to be slight, though I have no qualms with describing a star that is different from ours or a difference in daily hours. An additional moon or a moon that is clearly different from ours is fine if it helps accomplish what I’m looking for.

The inhabitants of this world are not space faring or remotely as technologically advanced we are; they are fairly primitive. My concern was the odd year length, which is pivotal to the story, and the idea that the planet’s rotation and star could not realistically be exact to Earth’s, which is more than fine, I’m just unsure how to figure this out on my own.

I would’ve posted this on the astronomy stack, but was led to believe by a question on meta that they disapprove of questions about imaginary planets there. However, if this question is more appropriate for that site, please let me know and I’ll remove it from here. Also, if there is any additional information that I should add to make my question easier to answer, just say the word and I’ll do my best. Thanks in advance.

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  • $\begingroup$ When you say days, which days are you referring to? The planet days, or our days? $\endgroup$ – L.Dutch - Reinstate Monica Dec 20 '19 at 4:10
  • $\begingroup$ @L.Dutch - That... is a good question. I suppose I’m referring to the planet’s days, but hoping that the number of hours in each might be comparable to ours. I started off thinking of this world as your everyday fantasy world, set with an identical sun, but not Earth, because it just can’t be, if you know what I mean. My problem arose with the 8 months thing, because it’s important to the story that stuff like that is either a multiple of or divisible by eight. So, I guess you could say I started off thinking of it as ‘our’ days, but then realised that their length might... $\endgroup$ – MooNieu Dec 20 '19 at 8:09
  • $\begingroup$ @L.Dutch - ... - might need to be different, if that makes any sense. That’s the best way I can explain it... $\endgroup$ – MooNieu Dec 20 '19 at 8:11
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You're probably looking at a K-type main sequence stars (also sometimes referred to as Orange dwarves, though astronomers apparently don't like this name much). These stars, bigger than red dwarves, but smaller than G-type main sequence stars (such as Sun), are considered the best candidates in the search for extraterrestrial life, simply because they don't suffer from many troubles of red dwarves, and because they're more common than G-type.

With a help of orbit calculator, if the star's mass is 80% of mass of the Sun (that is, the star is almost a G-type), and the distance between star and planet is around 0.7325 AU, you get 255.9 day orbit. This is well within habitable zone of such a star. Size/mass of the planet is irrelevant for this calculation.

As for features of living around such star, check out this wiki link as a starting point for your research. Overall, there are not many differences, but such "sun" would appear slightly larger than our sun, but a tiny bit dimmer and with more orange light. Days on your planet would probably be slightly longer, but this seems to not be a necessary result.

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