# Donut-shaped planet
**URL:** https://boards.straightdope.com/t/donut-shaped-planet/961249
**Category:** In My Humble Opinion
**Created:** [March 17, 2022, 3:42pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249 "2022-03-17T15:42:02Z")
**Posts on this page:** 20
**Page:** 2
### Author:  [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)
#### Post date: [March 17, 2022, 4:51pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/21 "2022-03-17T16:51:33Z")
> [@panache45](#):
>
> Where do people get the idea that in an infinite universe, ALL things MUST exist? That’s stupid.
I did not state that it must exist. This isn’t Factual Questions, it’s the forum for asking opinions. Things like this are fun to speculate on. I’m asking for opinions.
No need to be rude.
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### Author:  [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)
#### Post date: [March 17, 2022, 5:01pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/22 "2022-03-17T17:01:10Z")
> [@kanicbird](#):
>
> OK then what about the star itself? A donut star possible? If so that might be easier to find then such a planet.
A stable one that lasts billions of years? No.
But it may not be totally impossible for a star during its evolution to have a donut-phase, though it would almost certainly be short lived as it would not be stable.
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### Author:  [@Knowed\_Out](https://boards.straightdope.com/u/Knowed_Out)
#### Post date: [March 17, 2022, 5:08pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/23 "2022-03-17T17:08:29Z")
> [@Sage\_Rat](#):
>
> I’m not sure that you would experience the spinning except as a gravitation-like force. Your balance would naturally orient you to be upright and the land around you would be stable. You might notice the sun moving across the sky several times a day but that wouldn’t be enough to make you dizzy, by any sense.
I got the impression that it requires off-the-charts rotational speed to achieve the torus shape and create the donut hole. It’d at least be the equivalent of existing in a constant state of hurricane.
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### Author:  [@Knowed\_Out](https://boards.straightdope.com/u/Knowed_Out)
#### Post date: [March 17, 2022, 5:14pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/24 "2022-03-17T17:14:17Z")
> [@kanicbird](#):
>
> OK then what about the star itself? A donut star possible? If so that might be easier to find then such a planet.
There’s a Netflix series coming up based on The Three-Body Problem, which involves three suns orbiting each other. Not a donut, but definitely a cataclysm of galactic proportions.
> **[The Three-Body Problem (novel)](https://en.wikipedia.org/wiki/The_Three-Body_Problem_(novel))**
>
> The Three-Body Problem (Chinese: 三体; lit. 'Three-Body') is a novel by the Chinese science fiction author Liu Cixin, the first within the Remembrance of Earth's Past trilogy—though the series as a whole is often referred to as The Three-Body Problem, or simply as Three-Body. The series portrays a fictional past, present and future wherein Earth encounters an alien civilization from a nearby system of three sun-like stars orbiting one another, in an example of the three-body problem in orbital m...
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [March 17, 2022, 5:16pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/25 "2022-03-17T17:16:34Z")
For some reason the links to articles about toroidal planets in this thread don’t seem to work.
Here’s Wiki on the subject
> **[Toroidal planet](https://en.wikipedia.org/wiki/Toroidal_planet)**
>
> A toroidal planet is a hypothetical type of telluric exoplanet with a toroidal or doughnut shape. While no firm theoretical understanding as to how toroidal planets could form naturally is necessarily known, the shape itself is potentially quasistable, and is analogous to the physical parameters of a speculatively constructible megastructure in self-suspension, such as a Dyson Ring, ringworld, Stanford torus or Bishop Ring.
> At sufficiently large enough scales, rigid matter such as the typical si...
and a nice analysis by Anders Sandberg.
[http://www.aleph.se/andart/archives/2014/02/torusearth.html](http://www.aleph.se/andart/archives/2014/02/torusearth.html)
> [@](#):
>
> It looks like a toroid planet is not forbidden by the laws of physics. It is just darn unlikely to ever form naturally, and likely will go unstable over geological timescales because of outside disturbances. So if we decide to assume it just is there, perhaps due to an advanced civilization with more aesthetics than sanity, what are its properties?
We probably won’t find one, but we might (eventually) be able to make one, albeit with difficulty. And no, things won’t fly off the equator because of centrifugal force - although they will be somewhat lighter there.
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### Author:  [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)
#### Post date: [March 17, 2022, 5:24pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/26 "2022-03-17T17:24:58Z")
There are some off-the-charts spinning things out there.
[**PSR J1748−2446ad**](https://en.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad#:~:text=PSR%20J1748%E2%88%922446ad%20is%20the,confirmed%20on%20January%208%2C%202005.) is the fastest-spinning pulsar known.
The neutron star is assumed to contain less than two times the mass of the Sun, within the typical range of neutron stars, its radius is constrained to be less than 16 km. At its equator it is **spinning at approximately 24% of the speed of light** , or over 70,000 km per second.
No idea how things like this achieve those speeds.
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [March 17, 2022, 5:28pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/27 "2022-03-17T17:28:18Z")
> [@Sage\_Rat](#):
>
> I would lean towards the idea that any stable configuration is liable to pop up eventually but the longer and skinnier that something is the less connective power it will have against itself and the more likely that it is to get torn apart by collisions with random junk.
As mentioned, a ring planet has all the structural impossibilities of an artificial ringworld, plus the added concideration of just where is all that natural mass coming from.
Take for example Mercury. It has a diameter of around 3,150 miles and an orbital circumference of around 350 million miles. Turn that into a solid tube with the diameter of Mercury and that tube has around 1,650 times the volume of the Earth. If you take that to be 1,650 times the mass of the Earth, that’s 5 Jupiter masses of rock and iron.
(My math might be off on that, but it won’t be off by enough to make the idea more plausible.)
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### Author:  [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)
#### Post date: [March 17, 2022, 5:32pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/28 "2022-03-17T17:32:57Z")
> [@Knowed\_Out](#):
>
> I got the impression that it requires off-the-charts rotational speed to achieve the torus shape and create the donut hole. It’d at least be the equivalent of existing in a constant state of hurricane.
If there’s an atmosphere, I’m not sure how much the spinning of the planet would be affect it. The local sun could act like a constant pull, creating a thicker region of atmosphere that tries to move to stay pointed at the sun or the surface of the planet could act as such a sufficient brake on atmospheric movement that it’s not much different than Earth.
I’m not sure if it’s more or less likely for a donut to be nearer to its sun or further. But I think (?) it should be safe to say that it wouldn’t have a molten core or else it would be at risk of becoming unbalanced, breaking, and turning into a sphere. If it’s not molten and it’s more awkward to become a donut than a sphere, it’s more likely (?) to be non-smooth and imperfect than a spherical planet. So I would lean towards there being a fair amount of atmospheric friction at surface level - though I’m very far from confidence on that. Maybe a physicist has an opinion?
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### Author:  [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)
#### Post date: [March 17, 2022, 5:53pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/29 "2022-03-17T17:53:17Z")
> [@Darren\_Garrison](#):
>
> As mentioned, a ring planet has all the structural impossibilities of an artificial ringworld, plus the added concideration of just where is all that natural mass coming from.
Purely for the sake of argument (and I do mean that), let’s say that there’s sufficient material in a particular solar system for a hypergiant star. But, as it happens, only a white dwarf forms. There was 222 M☉ to be molded into shape and only 0.34 M☉ ended up becoming a sun. We have the grand majority of 222 M☉ still to build planets and whatnot with and - so long as we’re in a crazy stable, fluctuation and clutter free corner of the universe - that’s free to be allotted around into any stable arrangement that we could ever want.
It’s crazy unlikely but crazy unlikely is still not impossible and the quantities of trial cases are nigh unlimited from a practical standpoint, in the real universe.
I think the question isn’t about mass - clearly there’s enough mass in some solar systems to make a long thin ring of any size around a star - it’s more a question of exactly how clear and unperturbed a corner of the universe can ever be? Is there a theoretical minimum?
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [March 17, 2022, 6:14pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/30 "2022-03-17T18:14:30Z")
> [@Darren\_Garrison](#):
>
> As mentioned, a ring planet has all the structural impossibilities of an artificial ringworld, plus the added concideration of just where is all that natural mass coming from.
There’s no need to make the torus planet so big; one case investigated by Sandberg has 6 times the mass of Earth, and approximately the same gravity as Earth (on certain parts of the surface).
And the instability of a torus world is unrelated to the instability of a Ringworld; the main reason hoopworlds can’t exist is that they tend flow and form beads, which then coagulate into self-gravitating spheres (which will quickly collide with one another and coalesce into a single big blob).
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [March 17, 2022, 6:18pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/31 "2022-03-17T18:18:51Z")
Just to be clear, this is the sort of torus world I’m talking about, and the sort of torus world discussed in the wiki article. Some people seem to be imagining a much larger and thinner object.
[ ](https://upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Earthlike_toroidal_planet.png/640px-Earthlike_toroidal_planet.png)
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [March 17, 2022, 6:23pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/32 "2022-03-17T18:23:06Z")
> [@Sage\_Rat](#):
>
> I think the question isn’t about mass - clearly there’s enough mass in some solar systems to make a long thin ring of any size around a star - it’s more a question of exactly how clear and unperturbed a corner of the universe can ever be? Is there a theoretical minimum?
I mentioned the mass as a practical problem seperate from the fundamental physics reasons that a ringworld is unstable.
[https://boards.straightdope.com/search?context=topic&context\_id=818703&q=Ringworld%20unstable&skip\_context=true](https://boards.straightdope.com/search?context=topic&context_id=818703&q=Ringworld%20unstable&skip_context=true)
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [March 17, 2022, 6:25pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/33 "2022-03-17T18:25:05Z")
> [@eburacum45](#):
>
> There’s no need to make the torus planet so big
There is when I’m answering the question of if a ring planet can form around a star.
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [March 17, 2022, 6:42pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/34 "2022-03-17T18:42:46Z")
A ring around the star would quickly form into beads, coalescing into thousands of individual planets.
These thousands of planets would collide with each other and form larger planets, possibly flinging some of the resulting objects into wider orbits. Spectacular, but no good for habitation.
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### Author:  [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)
#### Post date: [March 17, 2022, 6:44pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/35 "2022-03-17T18:44:57Z")
> [@eburacum45](#):
>
> Spectacular, but no good for habitation.
You sound just like the contractor when I was trying to get to them to put a 3rd floor swimming pool into my home.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [March 17, 2022, 6:49pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/36 "2022-03-17T18:49:51Z")
> [@Sage\_Rat](#):
>
> But I think (?) it should be safe to say that it wouldn’t have a molten core or else it would be at risk of becoming unbalanced, breaking, and turning into a sphere.
At the scales of a planet, all materials are liquid.
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### Author:  [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)
#### Post date: [March 17, 2022, 6:57pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/37 "2022-03-17T18:57:58Z")
> [@Darren\_Garrison](#):
>
> a ringworld is unstable.
I should clarify that I’m talking about a toroid, not a ring (and I believe so was the person who I had been responding to).
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### Author:  [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)
#### Post date: [March 17, 2022, 6:59pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/38 "2022-03-17T18:59:16Z")
> [@Chronos](#):
>
> At the scales of a planet, all materials are liquid.
I suppose that that makes sense.
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### Author:  [@hogarth](https://boards.straightdope.com/u/hogarth)
#### Post date: [March 17, 2022, 7:02pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/39 "2022-03-17T19:02:11Z")
> [@Great\_Antibob](#):
>
> Look up “Ringworld”, which is basically this concept.
Note to mention “The Integral Trees” and “The Smoke Ring” (about a toroidal gaseous world).
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [March 17, 2022, 7:10pm UTC](https://boards.straightdope.com/t/donut-shaped-planet/961249/40 "2022-03-17T19:10:24Z")
> [@hogarth](#):
>
> Note to mention “The Integral Trees” and “The Smoke Ring” (about a toroidal gaseous world).
This is much closer to the toroidal planet concept. The Smoke Ring in Niven’s work includes a ‘shepherd’ planet, which smooths the ring into homogenity. If we ever make one of these worlds we will need to include some sort of shepherd mass or masses, maybe a ring of equally-spaced black holes.
[ ](https://i.stack.imgur.com/MBlBj.jpg)
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