Donut planet

Could a planet-sized object be donut shaped? From the definition of the planet, it's:

-is in orbit around the Sun,
-has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round) shape, and
-has "cleared the neighbourhood" around its orbit

If there however was a way for donut-shaped planet to exist, would it be able to hold atmosphere?

I really can't think of an way to have such a shape be  stable.
I suppose you could drill a really small hole straight through earth and claim it's topologically a donut.
In fact, it doesn't even have to be straight through, which means that either earth is already far too full of holes to be merely donut shaped, or topologists are crazy.

halo did it

how the hell could a donut-shaped planet form naturally?that would take some seriously fucked-up gravity.

Are you talking about a Niven ring, like in Halo or Larry Niven's novel Ringworld?

The math has been done.  A stable orbit is not possible, it would have to have massive engines all around the outer perimeter and it would have to compensate constantly for things as small as tiny unevenness of solar output.

If we magically put a ring around a star at a habitable distance it's like an egg balanced on one end, or a pencil balanced on its point.  Any instability causes positive feedback and it accelerates away from the center.  The egg tips over.  The pencil tips over.  The ring crashes into the sun.

Never played Halo, and, what I'm little ashamed, never read Ringworld. I mean any toroidal shape.

*ashamed of

and also, thanks for the answer.

What if we put that 'planet' out of orbit, cruisin through the space? Would it collapse or not? Would it be able to hold any atmosphere? Heating problems aside, only from gravitational POV.

I think halo is a pretty cool guy eh kills alins and doesnt afraid of anyhting.

It would need to have structural integrity capable of negating the gravity pulling opposite sides together otherwise it will collapse.

>>9
Unless the opposite sides were far away enough from eachother that the gravity between them was negligible compared to the gravity of the adjacent parts.

>>10
Then the gravity as seen from a small part of the torus would look similar to that of a infinite rod-like planet, except for a bias to one side due to curvature, right? There'd be a tendency to contract. You could spin it to counter that, but that'd bring other destructive forces.

I'm going to eschew calculations, simulations and the scientific method, and just pull an answer out of my ass; You can't have a stable torus-shape that is massive enough that the tube is held together primarily by gravitational forces.

>>10

The planet would have to be composed of some strong-ass material to withstand a collapse. Arches only work on earth precisely because the gravitational acceleration is less on a stationary surface.

Guys I think a planet with the curvature of a Moebius strip would sustain itself because if there is only one side how can the inside collapse inward when it is actually expanding outward??

>>10
The Earth isn't solid, it's like very very slow setting honey. Parts of Europe are still rising 10000 years after the ice cap's weight melted away.

>>1 I would have to say No, based on the assumption that an interstellar body must maintain an equal mass through out it's circumfrince. I hope that helps... 

>>13

wait a second
has anyone tried this???

Surely there must exist some kind of simulator where we could plug in the shape and orbital speed, and watch the spectacular collapse?

When considering feasibility of existance, one should also take into account the intermediate stages. It helps little if you find some peculiar theoretically stable form if you can't get to it via continua of other stable forms, with jumps where necessary. It's like... Oh, I don't know. Like building a stellarator, but you have to keep it running while you're assembling it?

Anything with as much mass at the Earth will collapse under its own gravity until it's a sphere.  You may recall that one of the components of the definition of "planet" is that it's large enough to become round under its own gravity.  The Earth is way bigger than the minimum size necessary to become rounded.

The only way around this is to make the object small enough that its gravity isn't strong enough to overcome its own structural forces.  One way is by making it small so that the gravity is small.  The other way is to make it out of some sort of undiscovered superstrong material.  Ringworld was made of such a material.  This is a completely separate issue from the question of whether it could have a stable orbit.  The issue here is whether the thing will collapse like a crumpled kleenex.

not the OP, but thank you ALL

>>19
He's stealing the mobius strip idea!

HEY I THOUGHT AND THEORIZED LONG AND HARD TO APPLY A MATHEMATIC MANIFOLD TO SPACE TIME
DO NOT FUCK THIS UP FOR ME!!!!

>>11, you may be on to something but you're falling a tiny bit short of grasping it.

We see torus-shaped planetary bodies all the times.  They're called RINGS or BELTS.  Saturn has a ring and our system itself has a belt.

Sure, these "objects" are too discontinuous to qualify as a planetary torus.  But good SciFi is made from how we think about how such a thing could happen.  Niven thought about how you could have a planet and have ZERO gravity; he came up with a gas torus around a neutron star, called the "Smoke Ring".

So, can we postulate a physical phenomena that has the end result of a rapidly spinning torus of asteroidal material that is so massive that the material crunches itself eventually into a torus-like shape?  Sure, there would be huge problems of surface instability, but that didn't stop Robert Forward when he wrote "Dragon's Egg" (about life ON a neutron star).  Why couldn't the surface be fairly trubulent, like having an Earth with fairly constant 6.0 earthquakes everywhere?

(Note also Forward wrote of a double planet, in "Rocheworld".  That guy blazed quite a trail for us to follow, huh?)

THINK IT THROUGH.  Math tards, get out your slide rules and see if it's possible for matter on a planetary scale to spin with such speed that it can form a "stable enough" torus of material about the diameter of the Earth.  The material should remain collected into the torus.  I'm particularly concerned about what happens to matter along the inner portion of the torus.  Will attraction by the rest of the torus fatally pull material from the inner surface?

Naturally, the atmosphere of such an object would be far more fluid, and it's certain that there would be a bulging disk of atmosphere in the donut hole.

ETHEREAL

Swift shimmering shadow steps silently; saddened, still softly severing serenities, slicing sympathy staggering sturdily; suffering sarcastic solace. Never noticing naïve naiads nor narrows nor necrotic nethers nestled nearby; naughty neutral nocturnal nexus nevertheless normally nostalgic notions; noteworthy nemesis neo neurotic neuralgia. Exceptional effervescing elemental ephemeral entity experiencing euphoria everlasting eternally eschew evermore, Ethereal