I have noticed that the planet will have a perpetual day zone, a perpetual night zone, and a ring, in its equator, with different grades of perpetual "twilight".

Am I right?

If I am, how will be those zones? An eternal desert and an eternal icezone?

What about the "twilight ring"? Which biomes will better fit there?

Thank you very much in advance.

  • 1
    $\begingroup$ There are many questions about this issue already. $\endgroup$
    – Vincent
    Dec 5, 2017 at 20:41
  • $\begingroup$ In this case, the planet will have a day equal to it's year. Although the zones will be there, it will still change like seasons. $\endgroup$ Dec 5, 2017 at 20:43
  • 2
    $\begingroup$ This cannot happen due to conservation of angular momentum. Effectively a spinning planet is a giant gyroscope and the poles remain pointed in the same direction at least over the short term. $\endgroup$
    – Slarty
    Dec 5, 2017 at 20:53
  • $\begingroup$ In case you actually just need those eternal daylight/shadow hemispheres, use "tidal locking". $\endgroup$ Dec 6, 2017 at 20:26

1 Answer 1


What you say is impossible: if the rotation axis is contained into the plane of the orbit, it will point to the main star only twice during the planet year. Therefore the cycle of day and night will last about half an year on each hemisphere.

This is more or less the situation on Uranus.

If the axis would be constantly pointing to the star, the planet would be locked and the rotation axis would then be perpendicular to the orbit plane.


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