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I have this race of space-dwarves and I need to make them homeless due to technological hubris of some kind: for plot reasons.

I think that if they were to attempt to build some kind of Dyson sphere and then it collapsed into the sun it could add enough mass to the sun to make it go nova or fizzle out or at least dramatically shorten the lifespan. Especially if the main elemental component of the Sphere was Iron, which can't be fused for energy.

  • Is this plausible?
  • How massive would the sphere-in-progress have to be to create a problem?
  • What would happen to the star?

Please bear in mind when answering

  • The dwarves in this setting are VERY co-operative
  • They follow the maxim: "If Brute Force isn't working, you're not using enough of it!".
  • Resources aren't a problem. -They have some sort of super-steel that is strong enough to be used in the construction of a Dyson Sphere, but if it would cause a more interesting result, then non-iron-based substances will be considered.
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    $\begingroup$ "If Brute Force isn't working, you're not using enough of it!" I should make that my motto as well. $\endgroup$ – Ambrose Winters Jul 16 '17 at 16:04
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    $\begingroup$ First you need Lt. Col. Samantha "You know, you blow up one sun and suddenly everyone expects you to walk on water" Carter. $\endgroup$ – Mazel Jul 16 '17 at 22:47
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    $\begingroup$ "And this switch turns off the neutron star containme...(click)...aww crap." $\endgroup$ – Spencer Jul 17 '17 at 23:59
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I really don't have the astrophysics background for a detailed calculation, but I do understand that in order to destabilize a star by throwing mass at it you must use a lot of mass. In order to get some ballpark figures, suppose the star is Sun-like and the Dwarves have managed to build a Dyson sphere of solid iron at a distance of 1 AU. The volume of iron contained in said Dyson sphere can be calculated easily:

$${{4 \pi} \over {3}}(R^3-r^3)$$

where $R$ and $r$ are the outer and inner radius, respectively. For a Dyson sphere with a thickness of 1 m, that gives $2.8\times10^{23} m^3$, which is four orders of magnitude smaller than the volume of the Sun. Any main-sequence star will be a lot less dense than iron, and anyway you could use some denser material, thus bringing the thing down to three orders of magnitude.

Or you could make the wall thicker. A Dyson sphere with a 100 m wall of osmium at 1 AU would have a mass of $6.3 \times 10^{29} kg$, about one-third of the Sun's. That should be fairly destabilizing, I think, but as I said, I have no idea what it would actually do.

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  • $\begingroup$ The sun is about 3 times denser than iron because its gas is crushed together hard. $\endgroup$ – Donald Hobson Jul 17 '17 at 22:56
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    $\begingroup$ @DonaldHobson The average density of the Sun is 1.408 g/cm³, less than a fifth of the density of iron. $\endgroup$ – pablodf76 Jul 18 '17 at 0:23
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ADDENDUM: In response to @Frostfyres comment below, here is the idea summarized: Add large quantity of fissile element to star in hopes of prolonging its life. The result is other than is intended.

ADDENDUM 2: From the comment, @Douglas looked the linked question from the astronomy stack and took away that the answer was "No". The answer there is actually "Maybe". Below is the relevant text copied from that answer. .

If you have a material inside that slows the reaction, absorbs and re-admits Neutrons you could probobly generate a sustained burn - similar to what happens inside a nuclear plant while maintaining enough gravity to keep the object in one piece and over time, That would heat up and glow like a star in time and last for a while.

In my answer the dwarf describes that this, in their pride, is what the dwarves tried to do. As regards "completely unrelated" I would plead it is not complete: the answer includes a dwarf, and a star.

ADDENDUM 3 From @MozerShmozer's comment. The link is about a large mass of fissile material. Q:Could it act like a star? A:Maybe it could. OP: The dwarves have a fusion star. They screw it up. How? My answer: With their skill they build it a fission heart, like the thing described in the link. They put it in their fusion star. It is classic hubris: supreme technological skill versus the inevitability of death. This makes for a good story because as in other cases when science opposes death, the dwarves do not need to screw up or blunder. They can be correct in their estimation of their skill, succeed in their attempt and then be horrified at the result.

It is ironic that I thought this was such a cool scifi answer, but failed so hard to convey it to an audience I thought would be right there with it. I will keep the day job.

---


“We knew that soon Grandfather would die, and burst. When he ran out of the light stuff that drives him.”

Tys watched the dwarf roll something between his fingers as he spoke – a well worn piece of some machine, she guessed. It shone like nickel. “You call your sun Grandfather?”

He nodded, the nickel piece clicking against his rings. “Because we love him, and we hide from him. And we knew he would die. We thought of a way to help him.” The dwarf flipped up the bit of metal and quickly used it to deeply scratch a perfect circle in the table top, dividing it neatly into pie shaped tenths. He blew the scratched pieces of table away and then set the metal bit down in one section. “Fusion happens only with the light stuff – the starstuff.”. He looked at the circle and back at Tys, apparently thinking that this scratching would serve as some sort of visual aid.

Tys nodded. The pie on the table did not mean much, except that they should cover it with a placemat before they left. But she did understand fusion.

The dwarf, satisfied, looked back down and rolled the metal bit over two pie slices. “When the light stuff is gone, he dies. Withers, or bursts. But we thought – could he live again, but in a different way?”. As he spoke, the dwarf looked past Tys' ear at something that was not there. “Like the ones who dive deep when they die, living in the dark tunnels on the glow of the earth?”

Tys looked at him quizzically. “Dive deep?”

He cut her off, his mind far away in a different place and time.. “We had long known the method to make energy from the heavy stuff – the fission. The second greatest energy. Some thought the first.” He moved the metal piece across the circle to rest in a different slice, and laid his thick finger beside it. “And then in space we found the burst heart of a star long dead, made only of the heavy stuff. More than any could use in a thousand thousand lifetimes. And we thought: if with our skill we could rebuild this dead heart and give it to Grandfather it could become his own heart. And in his grip that dead heart could come back to life with fission. He would gain a new youth. New life.”

The dwarf fell silent. “So?” asked Tys. “Did you give him the dead heart? Did it work?”

The dwarf scooped up the old metal piece, gripping it tightly in his palm. She could see the tendons stand up on the back of his hand. “Yes we did.” He looked at her bleakly. “And yes… it did.”

https://astronomy.stackexchange.com/questions/10294/is-a-star-powered-by-fission-possible

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    $\begingroup$ I'm not sure this qualifies as an acceptable answer. One has to follow the link and read to have any understanding of how the rest of the answer applies to this question. Users shouldn't have to leave the site to get the full answer. $\endgroup$ – Frostfyre Jul 17 '17 at 12:40
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    $\begingroup$ This doesn't answer the question. On looking at the other question you linked, the answer to that question is essentially "No". Nice prose but this is useless to me and completely unrelated to the question. $\endgroup$ – Douglas Jul 18 '17 at 10:44
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    $\begingroup$ Your link is unrelated to the current question. This question is about a fusion star, and the link is about a hypothetical fission star. Those are not the same. As such, I see no reason to believe that adding a large amount of fissile material to the core of a dying star would accomplish the stated goal. On top of that, your answer doesn't actually even explain what happened. What did the dwarves actually do to their star? How did it succeed and fail at the same time? What actually happened? $\endgroup$ – MozerShmozer Jul 18 '17 at 16:09
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    $\begingroup$ Actually you could just wrote the answer: "The dwarf tried to revive the dying sun (because of the failing fusion "heart" - it will deplete the hydrogen fuel soon), so they tried to give it a "fission heart", and in process, it explodes. I enjoy reading your story, but I think providing a direct, tl;dr answer is better. People should be able to scan your answer and find the most important part of the answer. $\endgroup$ – Vylix Jul 18 '17 at 19:24
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    $\begingroup$ Can you try to weave in the addendums (addenda?) so the way they modify the original answer makes a bit more sense? Thanks. $\endgroup$ – HDE 226868 Jul 18 '17 at 21:25
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One Thing that the space dwarves may have done is in their home system their star was reaching the end of its current stage of life and was either going to expand into a red giant (consuming most of the planets) or go super nova. The dwarves in an attempt to prolong the life of their star they attempted to remove mass from their star in a process known as star lifting. (https://en.wikipedia.org/wiki/Star_lifting) However since I think they would probably use the Centrifugal acceleration method since it's the fastest it puts anything in an equatorial orbit of their star at risk of being hit by greatly increased solar winds if the collecting device fails

Your dwarves could have been gathering mass from the star at a frightening rate when one of their collectors failed bathing their home system in strong solar winds, bleaching the surface of planets and burning stations out of the skies. The only survivors would be those on the ring around the sun which is generating the solar winds and those in the furthest reaches of the system with their homeworld destroyed. Without the support of the rest of their civilization the starlifing stations quickly succumb to their hostile environment and fall into the star with its occupants fleeing. At this point nature takes its course and the star that was going to go super nova anyway continues to do so, the dwarves having failed to remove the mass necessary to keep it alive.

I know this answer doesn't answer your question as intended but it does make your space dwarves homeless by their own hubris.

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I'm not sure on this one but it's at least in the realm of plausibility:

The dwarves really like their star system but it doesn't have enough planets. Thus they go out to other stars and find planets they like and bring them home. They have a stardrive powerful enough to boost planets to high relativistic velocities. They do not have FTL communications.

One day there's an accident. Just before deceleration was to commence a planet they were bringing home suffers a collision with a substantial body. The impact was about as much as the planet could take without being destroyed in the process. The stardrive was destroyed and the crew killed.

The dwarves were being careful in moving their planets, they always ensured that at no point in it's trajectory would a planet be dangerous if they lost control. They carefully kept the path of the planet from intersecting their star--but the impact was off center, the planet was deflected slightly. It plows into their star. Since they have no FTL capability they do not know anything is wrong until they see the flash of light and by the time they see it it's far too late for an intercept mission.

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  • $\begingroup$ It would have to be one hell of a planet to blow up a star... I think it would have to be another star being brought into the system. I remember watching a documentary once that claimed a white dwarf colliding with the sun would explode it. $\endgroup$ – ApproachingDarknessFish Jul 18 '17 at 8:15
  • $\begingroup$ @ApproachingDarknessFish No, it's not the energy delivered by the planet, but the fusion that it ignites. The idea is to ignite runaway fusion in the outer layers of the star. $\endgroup$ – Loren Pechtel Jul 19 '17 at 14:47
  • $\begingroup$ I remain unconvinced that a planet could impart enough energy/pressure to initiate fusion... but as the question doesn't call for hard science I'll refrain from downvoting. $\endgroup$ – ApproachingDarknessFish Jul 19 '17 at 20:53
  • $\begingroup$ @ApproachingDarknessFish There most certainly would be some fusion--hitting at relativistic speed is enough to cause fusion the point where the planet is hitting the star. The only question is whether the energy density is high enough to cause a powerful enough shockwave to cause fusion as it passes. $\endgroup$ – Loren Pechtel Jul 19 '17 at 23:14
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They could have a technology that was able to manipulate basic constants of physics, leading to the fusion rate of the star increasing by many orders of magnitude. Increasing fusion cross-sections would make starship fusion drives far easier to produce.. accidentally applying such a field to a star would cause problems.

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Only because I recently finished the Three Body series and this would qualify as an answer to the question asked. Also, this answer contains some details from the third book that might qualify as spoilers.

One of the highest of high-tech things a civilization in the novels can do is manipulate dimensionality. After finishing the book I thought, "hold on, if it's possible to create a 2 Dimensional space that upon coming in contact with 3 Dimensional space it sucks everything in like an unstoppable black hole (literally causing the collapse of the three dimensional universe down into two dimensions), how did a civilization test this technology?"

So there you go:

A civilization is mucking about with dimensional physics, inadvertently creates a chunk of 2D matter which then proceeds to consume their star system, collapsing everything down into an intricate 'painting.'

Oops.

Heck, it doesn't even need to be this. You could pretty much pick any technology that tries to screw with the laws of physics. FTL travel, teleportation, wormholes, time travel... (typing those out it occurred to me that they're almost indistinguishable) ...and something went Terribly Wrong and it destroyed the entire star system.

(I'm immensely amused by the idea of mucking about with time travel and inadvertently sending the whole star system a billion-billion years into the past/future)

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  • $\begingroup$ Opening a wormhole that passes through a star... $\endgroup$ – SparK Jul 18 '17 at 16:58
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The amount of material required for a Dyson Sphere is orders of magnitude more than exists in the solar system. Perhaps the simplest solution is that they were creating a rotating, habitable Dyson Ring and cannibalized the planets in their solar system, including their home world, to build it. Then a failure in the rings drift correction system, an asteroid, or a huge solar flare destroyed the Dyson Ring and left the dwarves without a planet. This leaves them homeless, even if their star still exists.

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  • $\begingroup$ They need to keep their planet. A main aspect of their story is they leave their solar system by turning their homeoworld (A moon of a gas giant) into a rocketship. $\endgroup$ – Douglas Jul 19 '17 at 6:15
  • $\begingroup$ But that's a good idea. $\endgroup$ – Douglas Jul 19 '17 at 6:16
  • $\begingroup$ Ah, I didn't catch that from the question. To stick with you're current plan then, the answer is yes, but I'd go with a tiny star. A brown dwarf can be no bigger than jupiter and yet provide enough light and energy during it's early life for a nearby moon to be habitable. It would quickly fizzle out though and fusion would no longer take place rendering the moon uninhabitable which would provide good incentive for your dwarves to attempt to prolong it's life. $\endgroup$ – wackozacko Jul 19 '17 at 17:29
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The space-dwarves are using super-steel to build their Dyson sphere. Since resources are no limit, they decided gather iron and the other elements needed for their super-steel from systems out to, say, one thousand light years. Their super-steel is mainly iron in the form of steel compressed to the density of white-dwarf matter. One ton in the cubic volume of a match box.

If the space-dwarves can turn their home-planet into a spaceship, this should be trivial exercise in alloy production and fabrication.

They tend the mass of their Dyson sphere to provide gravitation to enable the space-dwarves to live in comfort on the surface of the sphere. "Resources aren't the problem." the mass of their sphere will be approximately ten percent or more of the mass of their primary star. They will also import atmosphere for their sphere. Now the ideal method for transporting super-steel and atmosphere via long-range teleportation.

Unfortunately, the space-dwarves lack the facility and subtlety in navigation and guidance to ensure their teleported goods arrive precisely and accurately. This is to be expected if their maxim is: "If Brute Force isn't working, you're not using enough of it!". The result is ten percent the mass of their primary star in form of super-steel Dyson sphere components are accidentally dumped into their star.

The space-dwarves' star will be contaminated with excess iron. Iron is the least fusionable of the elements. Thermonuclear fusion will come to a halt in the poisoned star. A large amount of the star's thermal energy will be lost in melting and vaporizing the white-dwarf dense super-steel. There will be disruptions to the star that could lead to a nova. It is expected there will be massive disequilibria in the star. This could result in flare activity and excessive coronal mass ejections.

The space-dwarves will have no choice, but to head for deep space in their home-planet converted into a spacecraft.

Astrophysicists from nearby technical civilizations will arrive in droves to study the effects of iron pollution in the star.

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  • $\begingroup$ But you think if this happened a nova would be the result? $\endgroup$ – Douglas Jul 20 '17 at 18:24
  • $\begingroup$ Because my answer assumes large pieces of white-dwarf dense super-steel is dumped inside the star, it results will be chaotic and unpredictable. Normal flows of energy will be disrupted. A nova is possible outcome. If the pieces are large enough they could puncture parts of the star like a bubble and radiant energy could erupt. Basically, that's a nova. $\endgroup$ – a4android Jul 21 '17 at 7:25
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Self aware bombs with faulty logic.

From John Carpenter's early work Dark Star we know of at least one way to accidentally blow up a star. The star bomb was at least somewhat self-aware and goal driven. Its purpose was to blow up stars, and by George, it contrived logic needed to accomplish its purpose.

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