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So, this is an idea I am throwing around for my world, but not one I am committed to, but I am interested in it to see if I would like to do it.

Basically, my fictional world orbits a cool, boring, red-dwarf star very closely, so closely that it completes it's orbit in 4 days (it's a modified version of a real system, and I can't move the orbit out). I currently have it rotating, rapidly, along it's axis at 0 degress along with every other world in it's system; but if I were to tilt it so that it did have seasons, my question is:

What would seasons be like if they were only one day long?

Points to consider:

  • whether or not the seasons would even be noticeable
  • whether or not there is enough time for the seasons to alter the climate

The seasons are still caused by axial tilt, of course; it's just that the planet orbits its star so closely that there's only a day between the solstices and equinoxes. I am currently under the impression that these over-short seasons would not generate any weather or climate different from a 0 degree world, but do I really have the right idea?

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    $\begingroup$ Because of 'thermal mass', if seasons were very rapid temperatures would likely average out such that there were no seasons, just wind.. lots of wind. $\endgroup$
    – Richard
    Jan 23 at 1:10
  • $\begingroup$ +1 interesting question. At first glance, I agree with @Richard.. when the seasonal cycle is only 4 days, the atmosphere would not have time to move and cool off, or heat up anywhere. Maybe you would need a second star near, warming up the back side and widen the inhabitable ring, periodically ? $\endgroup$
    – Goodies
    Jan 23 at 10:47

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Assuming your world isn't tidally locked, 4 seasons, each a day long would be noticable, especially to those further from the equator.

Day 1. Vernal equinox in the south. Autumnal equinox in the north. Day vs night about the same all over.

Day 2. Summer solstice in the south. Winter solstice in the north. A very long bright day in the far south. A very long dark night in the far north.

Day 3. Autumnal equinox in the south. Vernal equinox in the north. Day vs night about the same all over.

Day 4. Winter solstice in the south. Summer solstice in the north. A very long dark night in the far south. A very long bright day in the far north.

This should be far too fast to seriously alter temperatures or plant growth.

Edit: The above description works best for those living along the longitude where the solstices/equinoxes happen at solar noon. For those living where these happen at midnight, days will be a bit weirder.

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    $\begingroup$ Ooh, I like this. Both Longitude and latitude matter. I wonder what the days would be like on the different parts of the planet. $\endgroup$
    – skout
    Jan 23 at 21:00
  • $\begingroup$ @skout - I'd love to see a simulation of what this would look like from the ground, preferably with a way to select lattutude and longitude. $\endgroup$ Jan 24 at 9:25
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Very Close

The planet is very close to its star. So (like mercury or earth's moon)

  • its Orbiting period = Rotation period.

  • It will always have same side towards its star.

  • Its side towards the star will always be bright and hot.

  • Its side away from star will always be cold and dark.

No Seasons

There are no days and nights.

There are no changes in climate therefor no seasons.

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  • $\begingroup$ Maybe you need to expand this answer a bit. Spin angle in respect to the stellar equatorial plane and an oblique orbit angle in respect to the equatorial plane would indeed disappear, with a tidal lock... However, a tidal lock planet can have an elliptical orbit. That would be not applicable here with only 4 days orbit.. but other things may count: your star could be a variable sun, or two suns could cause periodicity in sunlight, having seasons as a result. Refer to this topic: worldbuilding.stackexchange.com/questions/177231/… $\endgroup$
    – Goodies
    Jan 23 at 10:33
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    $\begingroup$ I understand the rotational speed of my world is inaccurate, but in order to tell the story I want to tell I know it needs a 24h day-night cycle. I know in reality my world would probably be tidally locked or (at best) have a 2:3 rotational resonance, but I am simply choosing to not be realistic in this area. $\endgroup$
    – skout
    Jan 23 at 20:59

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