Is this habitable moon possible?
I've already asked a similar question but i'd like more details.
This moon would be orbiting around a saturn like planet without rings. The host planet would be located in the habitable zone, allowing few of its moon to sustain life.
The moon would be 12000 kilometers wide, so it is big enough to have its own small magnetosphere. Thanks to that, it can orbit far away from its host planet.
I now want this moon to have a tilted orbit in such a way that when it orbits around the host planet, it will always receive light from the star because the light won't be blocked by the host planet when the moon is behind it.
Now I would like the moon to be non tidally locked so that it takes a few month to orbit around the host planet, but it would rotate on itself like earth would do in 24 hours, to have a day and night system.
how can this moon be non tidally locked? how can it be stable? I don't want the planet to be at the beginning non tidally locked and then become tidally locked after a certain amount of time, like normal moons would do. Phoebes or hyperion also are non tidally locked moons, but they are located far enough from saturn and are very small, therefore, my moon is 12000km wide!
How could it be a stable non tidally locked moon, that would rotate on itself in 24 hours? can it be caused by an asteroid that is orbiting around the moon and that's dragging it, causing it's rotation? Or a nearby other moon that is pulling the moon with it and causing also it's rotation?
I don't know how a moon like this could be stable and complete all these criterias so I would like a solution and details. Thank you!
This post was sourced from https://worldbuilding.stackexchange.com/q/86734. It is licensed under CC BY-SA 3.0.
1 answer
Let's break this down into the individual requirements.
The moon would be 12000 kilometers wide, so it is big enough to have its own small magnetosphere.
That's nearly twice the diameter of the largest known planetary moon, but it's not out of the realm of plausibility, so sure. You could say it's a captured planet or something.
Thanks to that, it can orbit far away from its host planet.
This is where you might run into problems. Going by the answer to your previous question, your moon would be orbiting at a distance of around 2 million km, so its distance from the Sun is going to vary quite a lot over the course of its orbit. And that's not taking orbital eccentricities into account. Depending on how quickly it orbits the planet, you might get some rapid fluctuations in temperature.
Fortunately, your next requirement makes this slightly less of a problem:
I now want this moon to have a tilted orbit in such a way that when it orbits around the host planet, it will always receive light from the star because the light won't be blocked by the host planet when the moon is behind it.
I can't think off the top of my head how much you'd have to tilt the orbit in order to avoid this, but a safe bet would be to give it the same tilt as the Earth's axis: about 23.4° As noted in the comments (thanks @pablodf76 and @bendl), you can achieve this with a tilt as small as 1.7° (even smaller if the orbit is further out). The larger the orbital inclination, the less distance there'll be between your minimum and maximum distance from the sun, but you'll start running into problems with parts of the planet being permanently light/dark.
Now I would like the moon to be non tidally locked so that it takes a few month to orbit around the host planet, but it would rotate on itself like earth would do in 24 hours, to have a day and night system.
You've answered your own question here. As you note, Phoebe and Hyperion are non-tidally locked moons, so this is entirely possible. Indeed, the answer to your previous question notes that larger moons will resist becoming tidally-locked for much longer, so your supermoon can very easily sustain its own axial rotation.
How could it be a stable non tidally locked moon, that would rotate on itself in 24 hours? can it be caused by an asteroid that is orbiting around the moon and that's dragging it, causing it's rotation?
Again, refer to your previous question. It must have already been spinning that fast (or faster) when it was captured by your gas giant. An asteroid isn't going to have enough mass to pull your planet round in circles like that.
Or a nearby other moon that is pulling the moon with it and causing also it's rotation?
Another nearby moon might affect its rotation around the planet (this is called an orbital resonance, and can be seen in the Galilean moons of Jupiter), and would also cause tidal flexing that would increase the moon's geological activity (again, see Io), but it wouldn't affect the planet's rotation around its own axis.
TL;DR: Can you have a habitable moon orbiting a gas giant, with an inclined orbit and its own day/night cycle? Yes, yes you can.
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