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Karagin-

Darkness is a friend of mine. Sometimes I have to beat it back, or it would overwhelm me. Shirley Meier

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The Wookiee, he's not wearing any pants!

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a donut-shaped planet with a moon on the central axis?

the gravitation would make the planet collapse and go ball-shaped before it can solidify in the process of its creation.
the moon inside of the planet is so close that tides would be devastating, it would also create earthquakes when it is that near.

I would also ask the question how the field of gravity around the planet is shaped, and if that might lead to the atmosphere flowing into the hole, wich would mean too little atmosphere on the planet-surface to breathe, and the moon would be slowed to a standstill.

then the system would probably orbit a sun, when the axis of the moons orbit is not vertical to the direction to the sun it might change its speed when changing its distance to the sun, im not sure if that would destroy the balance and let it crash into the planet

the gravity would pull on the planets structure and try to collapse the ring, if the planet has a glowing/semi liquid inside it would have to rotate rather fast to not collapse. im not sure if there is a shape in wich the rotation and gravity let the donut be stable, but a moving moon inside the hole makes it extremely unlikely that such a structure could exist.

it is still an interesting idea for a world for a novel.

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typos and spelling-mistakes are property of the finder. english is not my mother-tongue.

No sillier than Discworld...

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Yeah, not possible in nature. Laws of physics, hydrostatic equilibrium, and all that sort of thing.

Theoretically, it IS possible for a planet to spin so fast that it becomes visibly oblate; Earth is slightly oblate but not enough to notice with the naked eye. There are stars (Achernar being one) that are highly oblate due to their super fast spin, but they have a lot more mass and gravity to hold them together against the spin. Planets with very high spin rates are possible, but their structure would probably be relatively unstable, assuming they could form at all, and they most likely wouldn't be habitable.

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Be careful what you wish for. I might let you have it.

Actually, I'd say it COULD be possible, but there's a LOT of factors that would have to go JUST right, and the "planet" part certainly wouldn't be a perfect toroid.

BUT IF the period of rotation of the ring was so high that it counteracted the gravity of the opposing mass, you could probably get something similar, but it would more likely be a flattened disk like the rings of a planet, just solid. The material of the ring would have to be super-dense, and it would have to be spinning like a SOB making it highly unlikely to be habitable.

... and the wake of that moon bouncing back and forth would cause horrible quake-like effects in the structure. The materials of said world would also have the issue of likely being "sifted" by density, so less dense materials like water would end up on the inside and heavy metals on the outer diameter.

Such a structure could probably be MADE, but the odds of it being a natural occurrence are astronomically low... admittedly people say the same thing about life.

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