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Destroying Stars?

  1. Nov 13, 2005 #1
    Hello, all. This isn't entirely a real-life question, but I'd like to know your opinion. I'm a science fiction writer/astronomy lover trying for a "hard sci-fi" approach to the astronomy in my tale -- using as much real science as I can.

    So, I have a dilemma. Stars naturally die after fusing the hydrogen in their cores, unless they are massive enough and begin to burn helium (several possible elements later, they die anyway), and become white dwarfs, neutron stars, or black holes. That's the typical routine at the very basics, as I understand it. But, if one wanted to, how could one conceivably destroy a star before the end of its natural "life span" through technological means? Could it be "damaged" in any conceivable way?

    Any wild speculation is welcome, because I'm writing a futuristic universe where a lot more is possible than we can do today. Preferably, this technology needs to be quickly moved about and deployed, rather like a weapon of some kind than a complex setup that takes years to construct.

    And if somehow, this thread is in the wrong area, please feel free to move it. :)
     
  2. jcsd
  3. Nov 13, 2005 #2
    we could find some a way to decrease the hydorgen or acclerate the reacations but probally don't have the technology yet.I think we shouldn't find out so Terroist won't get any Idea's.
     
  4. Nov 14, 2005 #3
    Create an artificial black hole and fire it into the Sun. The black hole will then eat up the Sun from within, until there's nothing left but the black hole itself.
     
  5. Nov 14, 2005 #4
    learn how to control time, and fast forward the star 'till it's death.
     
  6. Nov 14, 2005 #5
    shoot it with a high powered particle beam coming from a source/laser head the radius of the earth... put a hole in it, and it will collapse on itself or defuse.
     
  7. Nov 14, 2005 #6
    alter some other larger bodies course nearby, and make them collide.
     
  8. Nov 14, 2005 #7
    pour a giant bucket of water on it.
     
  9. Nov 14, 2005 #8

    Danger

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    If you could manage to divert enough iron-rich bodies into the core (and it would take one hell of a lot of them), the fusion could theoretically be put out. Iron absorbs heat and neutrons without fusing. (Double-check me on that, Space Tiger.)
     
  10. Nov 14, 2005 #9

    SpaceTiger

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    I know some of these suggestions weren't meant to be taken seriously, but for fun, let's discuss a little of their astrophysics...

    One might be able to accelerate the nuclear reactions by introducing vast quantities of some mediator isotope, but that wouldn't destroy the sun, it would just cause it to expand and reach a new equilibrium. If the reactions increased the energy production extremely quickly, one might be able to blow the sun apart before it could equilibrate, but I'm pretty sure there aren't any known isotopes that could do this.

    Decreasing the hydrogen content is another option, but since the sun is made mostly of hydrogen, this would be practically equivalent to pulling it apart, piece by piece. The gravitational binding energy of the sun is

    [tex]E \sim \frac{GM^2}{R} \sim 10^{48}~ergs[/tex]

    so we won't be fulfilling these energy requirements anytime soon.

    If we were somehow able to make the sun inert (i.e. stop fusion), then it would seem to have no way to replenish the energy radiated away. Thus, it would cool, the pressure would fall, and the sun would begin to contract. However, this contraction is itself a source of energy -- in fact, they used to think that this was what powered the sun. This means that the sun will live for a while even after burning ceases...about 10 million years.


    This one's kinda tricky. A very low mass black hole would have no noticeable effect on the sun, while a very large one (of order the sun's mass) would gravitationally disrupt it -- but we couldn't create such a beast artificially. In the intermediate range, a black hole at the center of the sun might even make it live longer. The reason for this is that the lifetime of the sun depends on the efficiency of its energy source; that is, the more effectively it can turn matter into energy, the longer it can keep itself up from the pull of gravity. Other than matter-antimatter annihilation, accretion onto a black hole is the most efficient source of energy that we know of, converting of order 10% of the rest mass of its fuel into energy. If the star reached a stable equilibrium with the black hole at its center, then slow accretion onto the black hole could maintain the star for a very long time.

    There a lot of "ifs" in this one, however. It's not clear what kind of equilibrium (if any) the star would reach with a sizable black hole at its center. The efficiency of an accreting black hole is also extremely uncertain. Finally, depending on the initial mass of the black hole, it may be a problem even getting it to the center without seriously disturbing the star's structure.


    Shooting it with a laser beam wouldn't put a hole in it, but it would heat it up. Unfortunately (or fortunately), to have a noticable impact, you'd need an extremely powerful laser beam, powerful enough to provide an energy comparable to the gravitational binding energy I quoted above.


    This may be the easiest way to seriously disturb the sun, but it would be difficult to destroy it completely. Any close gravitational interaction with an object of comparable mass would likely strip a significant portion of the sun's envelope. After this, however, the sun would just settle into the main sequence configuration for a star of lower mass.


    It you pour on enough of anything, onto the sun, you can shorten its lifespan (water would boil before even reaching the surface and have no special effect). However, to shorten the lifespan to anything less than a million years, you would have to add on the order of 100 times the sun's current mass.


    Unless you remove the hydrogen, I wouldn't expect the addition of iron to have more than an order unity consequence for the burning rates. If this were the case, you could refer to my response to the first idea. If you added enough (many times the mass of the sun), then you'd be reduced to my last response to dgoodpasture2005.

    Really, I can't think of any remotely feasible methods of destroying the sun. Even if we were to somehow remove its source of pressure, its total mass doesn't exceed the Chandrasekhar limit, so it would form a stable white dwarf. We could hurl it at a supermassive black hole, but the nearest one is 30,000 light years away.

    For better or for worse, I think we're stuck with the sun. :smile:
     
  11. Nov 14, 2005 #10
    A white dwarf is fine. It doesn't have to be blown apart altogether, just without fusion in some way, shape, or form.

    Would draining away some of the mass work? I know stars are incredibly massive, but if there were a way to take a large chunk of mass out of the outer layers, perhaps it would cause the star to expand due to less gravity. After all, the core would remain untouched. I'm not quite sure what that would do to the structure, and if it would eliminate fusion or at least slow it down or decrease it in some way.

    Antimatter? Perhaps if some of the core could be neutralized, that would do something.

    And just out of curiosity, if rotation could somehow be stopped in any conceivable way, would that do anything?
     
  12. Nov 14, 2005 #11

    Danger

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    Thanks for the analysis of my post, Tiger. As always, I enjoy having new information from you.
    As to the original question, I've come up with a different approach that's guaranteed to work. Put the sun on the Maury show. It won't physically destroy it, but it will destroy its credibility.
     
  13. Nov 14, 2005 #12

    SpaceTiger

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    Draining the mass would just cause it to settle into a longer-lived main sequence configuration. Low-mass stars live longer because their equilibrium luminosities are lower and they exhaust their energy at a much slower rate.


    If you could get a hold of vast quantities of antimatter, that would do the trick. However, I would expect this to be even more difficult than taking the star apart, bit by bit.


    Not sure what you mean. I already explained what happens if fusion is stopped.


    The rotation of the sun is very slow (~25 days), so its structure wouldn't be changed much if it stopped.

    Keep in mind that all of these responses are to the question of destroying the sun. If all you want to do is wipe out civilization as we know it, only an order unity change in the sun's energy output would be sufficient.
     
  14. Nov 14, 2005 #13

    SpaceTiger

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    I think your best bet is to have your civilization arrange for a precision rerouting of another object's orbit, perhaps a nearby star or white dwarf. Of the methods mentioned so far, I think this has the least demanding energy requirements.
     
    Last edited: Nov 14, 2005
  15. Nov 15, 2005 #14
    okay...that was..yea...
    cd
     
    Last edited: Nov 16, 2005
  16. Nov 16, 2005 #15
    OK, what if a giant Dyson sphere was constructed around the Sun with perfect reflecting material on the inside, so that all radiation released by the sun was reflected back onto it? Wouldn't it heat up until it went nova?

    Also, what about the possibility of constructing or redirecting an otherwise existing wormhole that would suck the Sun away into another universe, or at least somewhere very far away in this visible universe?
     
  17. Nov 17, 2005 #16

    SpaceTiger

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    If you reflect all of the emitted energy back into the sun, then what you have, basically, is a non-cooling star. If it's not cooling, then the energy generated will go into increasing its pressure and, therefore, causing it to expand. However, when it expands, the energy generation rate goes down (nuclear fusion requires high densities), so this whole process will likely just make the star steadily larger at a rate that decreases with time. Even with a perfectly reflecting sphere, the process would be very slow -- I would guess the Kelvin-Helmholtz timescale, which is around one to ten million years. Also, there would still be some energy losses by neutrino emission and stellar winds, so in practice, you couldn't return all of the energy to the sun.


    Wormholes are always an easy out for science fiction, but it may not even be possible to create them, given the apparent violation of the laws of thermodynamics.
     
  18. Nov 17, 2005 #17

    Hurkyl

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    I understand that it takes a very long time for the energy produced by fusion to reach the surface of a star anyways -- no matter what you did to the star, wouldn't you still have to find something to do with the thousands of years worth of photons beneath its surface trying to get out? (or is it millions?)
     
  19. Nov 17, 2005 #18

    SpaceTiger

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    There are a variety of timescales on which changes in the sun can take place. Some of the most important ones are:

    Nuclear timescale - The approximate time it takes for the sun to burn the available nuclear fuel. This timescale is obviously relevant for the evolution of the sun, since this is the sun's energy source. In general, you'll see major changes in its position on the Hertzsprung-Russel diagram on the nuclear timescale. For hydrogen burning in the sun, it comes out to about 10 billion years.

    Kelvin-Helmholtz timescale - The time it takes for the sun to radiate away its gravitational binding energy. If nuclear burning were to stop or become insufficient for compensating the energy losses, this would be the approximate lifetime of the sun. It comes out to around 10 million years.

    Thermal timescale - This is the time on which the temperature profile of the sun changes. The virial theorem makes it so that the gravitational and thermal energies of the sun are about the same, so this timescale turns out to be approximately equivalent to the Kelvin-Helmholtz timescale.

    Diffusion timescale - The average time it takes for a photon to undergo a random walk from the core to the surface. I'm guessing this is the one you were referring to. I've seen estimates that range from 50,000 to 10 million years, but to my knowledge, this timescale doesn't play a big role in calculating changes in the sun, so the precise time isn't very important.

    Dynamical timescale - The time on which gravitational perturbations are communicated across the sun. It turns out to be comparable to the sound-crossing time, the free-fall time, and the hydrostatic time. For the sun, all of these come out to about 30 minutes.

    If we wanted the sun to be "destroyed" on any timescale that was relevant for a science fiction novel, the process would pretty much have to be occurring on the dynamical timescale. Most of the things suggested so far would change the sun on one of the first three timescales. The one exception (which I noted as being the most promising) was the one that involved a collision with another object. When the sun and the object collided, the sun would be disrupted on the dynamical timescale.

    Another process that's known to occur on the dynamical timescale is stellar pulsation. When a star is unstable to hydrostatic perturbations, it can pulsate. If the amplitude of these pulsations were large enough, presumably the star could be blown apart. Perhaps if there was some contraption that created gravitational perturbations at one of the sun's resonant frequencies, a futuristic society could succeed in causing the sun to pulsate itself to pieces. It's a bit far-fetched, but then science fiction usually is...
     
    Last edited: Nov 17, 2005
  20. Nov 18, 2005 #19
    I was about to suggest resonance. Is it possible to create as SpaceTiger suggested some sort of gravitational resonance in the Sun. I recall Nikola Tesla talking about how the Earth could be destroyed in under 2 years if the correct resonant frequency was achieved through explosive devices (I don't recall if they were in the kiloton or megaton range) set off with each recurring resonant wave. I believe that an explosion on this magnitude would have to be set off every 45 minutes for 2 years to destroy the Earth. However, after only a few weeks Tesla claimed that any surface topology of the Earth would be drastically destroyed as the surface rose and fell several hundred feet. I don't remember the exact setup for this scenario but hopefully everyone gets the idea. Granted this is not gravitational resonance, but if a similar effect could be employed on the Sun would this technique be possible? :confused:
     
  21. Nov 18, 2005 #20

    JesseM

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    Ha, that's awesome that Tesla was thinking about ways to destroy the earth. Doesn't sound plausible though--there's no getting around the fact that you need a huge input of energy to get all the mass of the earth up to escape velocity, and the energy generated by some explosions won't come close (the energy needed is estimated at between 2.2 * 10^32 and 3.7 * 10^32 joules on this star wars page written by an engineer). Resonance can't generate more energy than is put in by the external driver, can it? I suppose the stretching and compression of bonds between molecules that make up the object would be converting potential energy to kinetic energy at times, but at other times kinetic energy would be converted back to potential (like an object bouncing up and down on a spring) so there shouldn't be any net increase in energy over time, aside from the energy put in externally by the explosions.
     
  22. Dec 2, 2005 #21

    Art

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    How about artificially creating fusion points in other parts of the sun using the suns own material to feed the process thus causing a cascade effect to destabilize it?
     
    Last edited by a moderator: Dec 2, 2005
  23. Dec 2, 2005 #22

    SpaceTiger

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    To induce fusion, you'd have to artificially increased the temperature and/or density at some arbitrary point in the star. As soon as you did this, however, you'd increase the pressure surrounding that point, causing your enhancement to expand. This would quickly halt fusion. Even if you did this at a large number of points throughout the star, all you would be doing, effectively, is heating and/or increasing the mass of the star. The process would produce pressure waves, so if you tried to coordinate those waves, you might get some interesting results, but the required energy input would still be quite large.

    In real astrophysical situations, the best way to produce a nuclear runaway is with degenerate gas. In this case, the star is using degeneracy pressure (instead of gas pressure) to support itself from gravity. If you keep increasing the temperature in a degenerate gas, you can induce fusion reactions. In this case, however, the temperature enhancement won't spread out because the pressure mechanism is dependent only on the density of the gas. The fusion reactions will heat the surrounding gas, causing it to fuse even more. This will continue until the gas becomes so hot that gas pressure overcomes degeneracy pressure and the enhancement is able to expand. Examples of runaways like this are novae (on the surface of accreting white dwarfs) and the "helium flash" (in the cores of moderate-mass stars).
     
  24. Dec 2, 2005 #23

    Art

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    Hi ST,
    From your post above it sounds like you are saying this would work for some kinds of stars??

    What about a sort of fusion 'missile' rather than fixed points? Using this new super duper technology that will be available in the future if several fusion missiles were fired one after another into the star towards it's core on the same heading using the star's own material en route, much as a jet engine uses oxygen in the air, to power the fusion missiles would it perhaps then fuse a lot more material? Also would penetrating the shell of the core allow pressurised material from within to escape back up the 'tunnel' drilled by the missiles? It sounds like something that would make a big bang at least. :-) BTW as obviously ordinary matter would melt, the shell of the missile would be a containment field rather than solid matter.
     
    Last edited by a moderator: Dec 2, 2005
  25. Dec 2, 2005 #24

    SpaceTiger

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    None of the processes I described above actually destroy the star -- novae occur multiple times and the helium flash just leads to another phase in the star's evolution. If the object were degenerate, however, then the energy requirements for destroying it would be even larger than for the sun because its gravitational binding energy is much larger. The best way to destroy a degenerate object is to give it mass until it passes the Chandrasekhar Limit. When you do this to a white dwarf, you get a Type Ia supernova.


    What do you intend to put in this missile? Increasing the rate of fusion in the core was already suggested, so you may want to look at my response to that.

    The most efficient missile I can imagine would operate on matter-antimatter annihilation. The amount of antimatter that you would need is given by half the mass equivalent of the binding energy I cited earlier (~1048 ergs). Turns out you'd need about 10% of an earth mass. Forget about making/finding that much antimatter, imagine trying to contain it!


    Even if it's possible to create a containment field like you suggest, you have to keep in mind that the sun is made of gas. Even if you evacuate a region within the sun, the surrounding gas will quickly diffuse to fill it.
     
  26. Dec 4, 2005 #25

    Art

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    I bow to your greater knowledge as I know next to nothing about the subject but this surprised me. I'd have thought that towards the centre at the pressures involved the hydrogen would have been in liquid form or does the high temperatures prevent that?

    Also out of interest presumably the sun and it's planets formed out of the same raw material gas cloud and so was the earth's composition originally the same as the sun's and if so why has it changed so much and how long did the changes take?
     
    Last edited by a moderator: Dec 4, 2005
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