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.
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.
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.
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.
For some reason the links to articles about toroidal planets in this thread don’t seem to work.
Here’s Wiki on the subject
and a nice analysis by Anders Sandberg.
http://www.aleph.se/andart/archives/2014/02/torusearth.html
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.
There are some off-the-charts spinning things out there.
PSR J1748−2446ad 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.
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.)
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?
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?
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).
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.
I mentioned the mass as a practical problem seperate from the fundamental physics reasons that a ringworld is unstable.
There is when I’m answering the question of if a ring planet can form around a star.
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.
You sound just like the contractor when I was trying to get to them to put a 3rd floor swimming pool into my home.
At the scales of a planet, all materials are liquid.
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).
I suppose that that makes sense.
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.
