The admiral of a space fleet that belongs to a Type 3 civilization has been given orders to obliterate all planets within the habitable zone of a Sun like star.

Some of the planets have been identified as nests for the larvae stage of swarm of the star eating Space Locus. Death Star type destruction of the planets won't kill the larvae.

The weapon of choice: seed missile

The technology:

  • The "seed" of a seed missile is a microscopic black hole.

  • The initial size is due to safety reasons. The black hole will evaporate via Hawking Radiation if the containment field is compromised; no secondary explosions possible.

  • Because the initial size is useless, the missile has to charge the weapon while in-flight.

  • To charge the black hole, the missile taps into Dark Matter and grows the black hole like a crystal.

  • The missile can cause the essence of the black hole to precipitate into electrons, protons, neutrons, and elements. example: Uranium or a small Neutron Star. This is done with handwavy physics.

What does the missile need to do to cause the star to obliterate the planets? Would this be a Nova or Super Nova? How far out could the star obliteration stellar objects? asteroid belt? kuiper belt?


I'm editing this because I feel that I had describe the seed missile poorly. Instead of setting the describing of how it works at the beginning, let me first describe its effect.

The missile is a white hole weapon that can generate a maximum amount of mass - say 0.01 solar mass. This is a rewording of point 5 of the original description along with a new description of the upper limit of its capabilities.

  • This is done by causing a black hole to operate like a white hole.
  • The black hole doesn't have all the mass, the Dark Matter does - point 4 of the original description
  • The black hole is just there as an intermediate step for the Dark Matter -> Normal Matter conversion - clarification of points 2,3, and 4 of the original description
  • The size of the black hole determines the rate of the conversion. - new information
  • At launch, the size of the black hole is microscopic - ~27 micrograms. - point 1 of the original description
  • This allows the missile to maneuver normally at first and become a door stop if compromised. - point 2 of the original description

If this was a chemical reaction, it would be written similar to this:

dark matter -> black hole -> white hole -> normal matter

example usage place a stealth variant of the seed missile in an orbit almost parallel to a dyson-ring star defense system and crank it up to 0.011 solar mass.

other usage throw the seed missile into a star, have it create ?????? type normal matter, and watch the star "go BOOM". This question is about filling in that unknown.

Additional information on the situation

It is estimated that 0.000001% of the star systems in the one galaxy are infected. Each of those star systems need to be 99.44% cleansed within a 1 year time frame. That's 2500 star systems in 365 days. No, you can't split the fleet.

  • 8
    $\begingroup$ If "Death Star type destruction" is not bad enough to kill the larvae, then there's no guarantee that collapsing the system's star, even in supernova-type explosion, would do the job. Your "seed missiles" would have to strike every planet individually. $\endgroup$
    – Alexander
    Commented Jan 10, 2018 at 22:45
  • 1
    $\begingroup$ A type III civilization should be able to make Kugelblitz black holes and it's hard to see anything not being effectively destroyed by using a black hole. And handwavy physics does not mean you should invent something like "the essence of a black hole" - there just isn't such a thing and it sounds ridiculous. $\endgroup$ Commented Jan 10, 2018 at 22:55
  • 8
    $\begingroup$ "the missile taps into Dark Matter and grows the black hole like a crystal." — after handwave this big pretty much any outcome can go. $\endgroup$
    – Mołot
    Commented Jan 10, 2018 at 23:06
  • $\begingroup$ @Mołot Very true. That step is literally black magic, and sidesteps all sorts of issues, like what happens when the black hole starts spaghettifying your missile around it! $\endgroup$
    – Cort Ammon
    Commented Jan 10, 2018 at 23:38
  • $\begingroup$ The matter density within the sun is such that your blackhole would probably just be absorbed and do almost nothing. Even if it forms an event horizon the sun is still way more massive and will simply suck back in any ejected matter. I read some where the bigger mass wins, and there is no practical way you will be able to form a relevantly massive blackhole with your black hole missile. $\endgroup$
    – cybernard
    Commented Jan 11, 2018 at 3:42

9 Answers 9


As others said, if the larvae can survive the destruction of a planet by Death Star-type laser, blowing the star up won't help, and may even make things worse.

Fortunately, you are from a Type III civilisation, so you have better tools than crude star-blowers at your disposition.

Star flamethrower

If your resources at hand are limited, a cheap option is to use some local stellar engineering: dismantle a few planets to build a magnetic field controller around the star, and use it to push the plasma away, make a big hole and unveil the core of the star. While the surface of the star is at a frigid few thousand K, the core of the star is at millions of K, and it is under gargantuan pressures. This is where the actual fusion happens, but energy moves outwards through the layers of the stars ever so slowly, as it is, at this scale, incredibly opaque and insulating.

Once unveiled, with the sudden absence of pressure, it will violently expand. The effect will be akin to a solar flare, expect much, much bigger. Or, if you prefer, a star flamethrower.

This will roast any planet you are pointing it at, but it won't be enough to kill the larvae, or even blow the planet up, in fact. But you can use one device per planet and keep them firing for a long, long time. At some point, the star will start dimming as the now punctured core cannot sustain enough pressure to keep the same fusion rate. Decreasing the rate or pausing for some time should fix it, though. The star will also end up loosing mass, which may also be mitigated by dropping interstellar hydrogen or even recycling escaped hydrogen back into it, but the loss rate will still probably be too big to fully balance.

The idea is that maybe the larvae can survive an instant, violent event but not a continuous burning for a long time. The planet will slowly evaporate (be careful to not let spores escape in its tail), though it would probably be too long to evaporate them completely that way.

Even if it doesn't kill the spores, it should still work as a short-term, stopgap option, giving you a few thousand or million years to work on actual solutions.

Be careful though, this de-orbit the planets by pushing them away. Again, you can impact them with other celestial bodies, or more elegantly use those bodies as gravity tractors to pull them back in closer orbit. In any case, it is recommended to start building a Dyson Sphere around the non-holed parts of the star for powering local facilities.

Nicoll-Dyson Beams

As was mentioned already, Nicoll-Dyson Beams are useful tools in this case. As a Type III civ, you should have a few of those in range, or be able to build them if it happens to be an undeveloped sector, or they are all busy with more important projects. You can even use the aforementioned local Dyson sphere you are probably already building around the star.

Now, you could use those to cook the target planets, similarly to the flamethrower option but with more power. You should be able to end up evaporating the planet given enough time, though again be careful with flying spores.

Another option is to use them to move the target planets, either with direct localised evaporation and radiation pressure (as in a rocket or a laser sail), or by moving other celestial bodies and use them as gravity tractors. That way, you can drop the planets right in the star's core, and slow their fall down enough that they stay there. Again, make sure no spore escape into the star's atmosphere, but after long enough, it should be entirely sterilised.

The advantage here is fast response time, and once it is in the star core, light surveillance should be enough to make sure nothing escaped, freeing your time and resources for other projects.

Dead star billiard

If you fear that dropping it into the star won't be effective enough, I recommend sending a star remnant to the system and hitting the planets with it. While it may be tempting to hit them as fast as possible, and this should normally be enough, those larvae are good at surviving brief, violent events and may escape with the debris. In additions, relativistic debris spraying around are messy to clean up, and local sector population may complain, with good reason.

A better solution is to slow the remnant down as it arrives, and hit the planets with it in such a way that all will fall and stay into the star core. This can be seen as an upgrade of the previous option in that regard. The advantage is that the star mass will, to some extent, help keeping debris from flying around.

Be especially careful, though, as even a slow, controlled approach will have the planets breaking apart due to tidal forces, and the larvae may use the occasion to try and escape with great velocity by using varied tricks with the debris and the immense gravity of the remnant.

Note that if your star is not massive enough, you may want to feed it local interstellar matter, or merge it with another star. Keeping the planetary system in order can be a bit tricky, but nothing unfeasible.

Note however that merging two stars, in particular here when one is a remnant, cause a violent, energetic burst that you will want to plan for. Again, stellar manipulators like those used in the flamethrower option should help.

There are basically three types of remnants you can use, depending on what is lying around:

White dwarfs are the most abundant. They should be similarly sized as the target planet, but with a thousand times the gravity. This makes it the easiest to use, and the default choice if you are certain the larvae won't survive it. Honestly, I don't think anything like that could, but just in case...

Neutron stars are tiny and with an absurdly high magnetic field. Magnetars are a type of neutron star with an even more absurdly high magnetic field, be careful with those. The magnetic field can play both for and against you or the larvae, depending on the details. However, once the star and the planet are in contact, the planet should be crushed in short order at the neutron star's surface, releasing lots of energy in the process, including in exotically strong forms. (Again, be careful that the larvae don't use it to help or help concealing their escape) Honestly, I can't even imagine any spore type to be able to survive it, but if you really want to be sure...

Black holes are even tinier than neutron stars, and anything that enters will exit in a long, long time as scrambled Hawking radiation. Otherwise, it should be used pretty much like a neutron star, with less of a magnetic field. Easier or harder to work with, depending on the details.

Big black holes, depending on local availability

Depending on where the star system is, there may be a supermassive black hole in the vicinity. Even an intermediate black hole should work, as long as the event horizon is wide enough.

In this case, an efficient solution may be to simply drop the planets in it. For this, build a Skhadov thruster around the star. The simplest design is a partial Dyson sphere letting light out in the opposite direction of the movement (similar to a photon rocket). Using the flamethrower system may have better thrust, if less range (similar to a nuclear fusion rocket), but you only need to go as far as the target black hole anyway.

Once you are there, you simply have to move the target planet on a direct collision course - this time, the faster the better. The bigger the black hole, the less tidal effects, so the planet shouldn't make too much debris when crossing the Roche limit and starting to break apart. As always, of course, be careful of tricks from the larvae at this point, but once it has crossed the event horizon, you should be fine.

Whether to let the star pas the black hole by, put it in orbit or drop it with the entire system in the black hole just in case it would still be infected is up to you. If you do choose to drop the star an it is an intermediate black hole, though, be careful. The event horizon is probably too small for the entire star, so use your stellar manipulators to siphon it until there is only the core left. The core is more or less a white dwarf, and should be small enough that you can simply drop it.

  • $\begingroup$ From the Death Star link "It fragments in gobs of varied sizes and shapes, from dust grains to, possibly, some as big as the Moon or Mars." - the size of the chunks is exactly why I don't want to attack the planet directly with a Death Star or Kinetic Energy weapon. $\endgroup$ Commented Jan 11, 2018 at 22:55
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    $\begingroup$ I would use a low mass white dwarf. The higher bodies are much smaller than the targets, there's always the risk that some pieces are thrown clear when the planet crashes down on them at relativistic velocity. It's the easiest to handle and the biggest object. (Yes--white dwarfs get smaller as they get heavier!) If the pests can survive that then drop the white dwarf into orbit about a neutron star. Lower it's periapsis until it touches and is gobbled up. $\endgroup$ Commented Jan 13, 2018 at 5:22

Targeting the star is a mistake. It's too inefficient.

Consider Earth. Orbital distance: 149,600,000km. Radius: 6371km.

If the sun were to explode, sending energy in all directions evenly, by the time the energy to to the Earth's orbit, it would be spread across $2.8 \times 10^{17} km^2$. The Earth's silhouette is about $1.28\times10^8 km^2$, so the Earth will receive a $\frac{1}{(2.2\times10^9)}$ fraction of the entire explosion. 99.999999954% of the energy of the sun's explosion will go elsewhere, wasted.

The sun has $1.2 \times 10^{44}J$ of energy in it (total lifespan). With those numbers, about $10^{35}J$ of energy will hit the Earth. This is on par with the energy that strikes the Earth in one year. That's all. Compared to a Death Star that's not all that impressive. A minimum bound on the Death Star is $10^{32}J$, so this strike is a mere 1000 fold more powerful than the minimum bound for the Death star.

Worse occurs if the infestation is on other planets. The power of this strike falls off with the square of the distance from the planet to the sun. Mars's orbit is 1.52 times the distance, so it receives about 43% of what Earth receives. Jupiter will only see about 3.7% of the intensity that Earth does, so now we're starting to talk about striking these planets with just a little more than that minimum Death Star bound.

This just won't do.

So what can we do?

Well, one option is to just keep hand waving. Invent some new physics which permits access to far more energy than mere nuclear fusion would permit, but which only functions in the heart of a star (probably because it needs the gravitational pull to do its mumbo-jumbo). Make this star-killer weapon 1000x more deadly than the star itself.

Another option would be to handwave the ability to focus the direction of the energy. If we don't waste the majority of the energy on empty space, the sun is a lot scarier. If your weapon could do some handwave trick which permits ejecting energy like a firehouse directly at the infested planet, all those annoying knockdown factors can go away, and you can truly focus the intensity of the star onto the job.

The final option is to change the story. It's almost always better to strike the thing that needs striking, rather than striking some nearby innocent star. I'm assuming that's not an easy option for you, but it's always a good idea to remember that these worldbuilding ideas are not set in stone. There's always room to make changes.

  • $\begingroup$ I'm having trouble reconciling the statement that the Sun will provide 1.2e44 J over its lifetime (about 1e10 years) and that about 1e35 J reaches the Earth in one year, with the Earth covering about 1.3e-9 of a sphere centered at the Sun at radius 1AU. It seems to me that to a first order approximation, the Sun's energy output would be spread roughly evenly over the Sun's lifetime, so 1.2e44 J total over its lifetime becomes 1.2e34 J (1e-10) total output per year. Of this, about 1.6e26 J (1.3e-9) would reach the Earth. Your result seems off by nine orders of magnitude. Am I missing something? $\endgroup$
    – user
    Commented Feb 17, 2018 at 21:30
  • $\begingroup$ For whatever that's worth, the claims made in the linked Wikipedia article have varying degrees of citations, but it does have a cited claim that "Total energy from the Sun that strikes the face of the Earth each year" is 5.5e24 J, which is pretty close to my crude estimate of 1.6e26 J and quite far from your estimate of around 1e35 J. $\endgroup$
    – user
    Commented Feb 17, 2018 at 21:32
  • $\begingroup$ @MichaelKjörling Ahh, I think I see it. I mixed up "energy that hits the earth in a year" with "energy the sun emits in a year" The latter number is 1.2e34, which is close to the number I was looking at. $\endgroup$
    – Cort Ammon
    Commented Feb 17, 2018 at 21:51
  • $\begingroup$ I think the rest of the numbers hold up, just not my claim that it's relatable to the amount of energy that hits the Earth per year? $\endgroup$
    – Cort Ammon
    Commented Feb 17, 2018 at 21:53
  • $\begingroup$ I haven't double-checked your other numbers; it was the relationship between the claimed 1.2e44 J total over the Sun's lifetime and 1e35 J received by Earth in one year that seemed to not match. $\endgroup$
    – user
    Commented Feb 17, 2018 at 23:00

There are several reasons why firing your missile into the sun (instead of the individual planets) is a very bad idea.

For one, not all stars will form black holes after they die, but some will. If you consume all the mass of even a small star with a black hole, you now have a black hole that won't dissipate via Hawking radiation for some time; it's a navigational hazard if nothing else.

Second, you lose the ability to harness the energy of that star for other purposes and build your own strategic installations in that star system.

Third, you may not even get a nova or super nova effect. What we know about such processes is that they are a final release of energy by the star after it's expended it's nuclear fuel and the balance between its mass and its energy release is broken in favour of mass. Add a small singularity to the centre of it and the core (which is where the bulk of the nuclear reaction is taking place) may get consumed first, meaning that the energy can't escape the gravity the way it does when the collapse is natural. (This is admittedly scientific speculation)

Finally, if your larvae can survive the cold, the planets are now likely still orbiting a singularity with the same mass as the original star, so with the exception of no sun, are probably unaffected in orbits, etc. meaning that they'll just keep doing what they were doing.

Far better to aim your missile at the planet. It gets eaten by the small black hole, and that means that you now have a singularity with the mass of a planet orbiting the star, but Hawking radiation should take care of this reasonably quickly by comparison to a star mass (I don't have exact numbers) and in terms of navigation hazard, it only applies to in-system travel.

This is (more or less) the principle behind the red-matter detonations used by the Romulan mining crew in the first of the new Star Trek movies, where Vulcan is destroyed. Create a small black hole at the centre of a planet, and the black hole eats the planet but does virtually no other damage. The star is safe because the black hole is already in orbit of the sun, so to speak and the mass of the resulting black hole will almost perfectly match that of the planet it consumes, meaning that your system is still useable, just less one planet which in time will evaporate via Hawking radiation.


A micro black hole does not work as a weapon

This is demonstrated by Joe Kissling. For a very small black hole, in the range of a billion kilograms, the radiation pressure from the evaporation of the black hole will actually prevent anything from falling into it. Thus, it will evaporate faster than it can accrete additional material.

Now this is a reasonably useful weapon on its own, since it is putting out about a petawatt of power; about 10 times as much energy released by a hurricane. But it isn't really going to be sucking anything in to it. If you stuck one in the sun, again nothing would happen. It would no accrete matter and its petawatt power output would be something like 11 orders of magnitude less than what the sun is putting off anyways.


If you want to blow up a star for your story, just blow up a star. Don't justify it with some mumbo-jumbo about black holes.


"It's not the size that matters..."

Throwing more energy at a problem sometimes simply might not help. What matters are the means to do it, which would go into sci-fi and require some (or a lot) of handwaving to make it palatable to present-day readers.

Some examples:

  • TV series "Stargate SG-1" explained it away with removing enough mass from a star to offset the gravitational/fusion balance so that the star blows up. Question is, wouldn't you have to remove that much mass that the fusion reaction stops?

  • TV series "Star Trek: The Next Generation" features a device to "halt a star's fusion reaction". Now imagine it the other way round, to make the star burn up fuel for thousands or millions of years in a fraction of a second.


Blowing up the star would not help. Rather it would make matters even worse. If your 'larvae' are resilient enough to survive their planet being blown into its consituent parts, follow me through the following scenario:

  1. By whatever means, the central star of the system goes boom.
  2. The shockwave of the explosion expands with fractional-c, reaching the planet in the habitable zone any time between ten minutes or a hour
  3. The neutrino emissions may alert the beings if they're sentient and developed enough. Since they don't seem to be a localized threat, they may very well be - so some could leave in time.
  4. The shockwave would first strip away the atmosphere, then ablate the outer crust, the mantle, the core, and then blow the remains (the far side of the planet) to pieces.
  5. And that could mean that parts of the crust which had been the shadowed side of the planet may still be in pieces large enough for the larvae to survive, if they can survive the rigors of space.

Now that gives me an idea for a spore-like lifeform that actually uses this as a means to spread out through the galaxy. Develop on a planet, 'do something' to blow up the sun, then ride out the shockwaves to another solar system.

  • $\begingroup$ I'm trying to figure out Step 1 - How to make the star go BOOM? The other steps you have mentioned actually verify what I was thinking would happen when the star does go BOOM. $\endgroup$ Commented Jan 11, 2018 at 23:01
  • $\begingroup$ Two possible ways of 'how' I did list in the first section, sure. Though I was concerned that if 'blowing up the star in order to eradicate the pest' was an integral plot device - as in, they have to be all gone -, the blowing-up part may fall a bit short of what is desired. $\endgroup$
    – Anonymous
    Commented Jan 12, 2018 at 12:14
  • $\begingroup$ Part of the story is about the futility of trying to fight Mother Nature, even for an extremely advanced civilization. Although they can identify the star systems infected with the larvae, they can't identify the star systems infected with the eggs. $\endgroup$ Commented Jan 13, 2018 at 14:40

Starting from what you say it can be done...

example usage place a stealth variant of the seed missile in an orbit almost parallel to a dyson-ring star defense system and crank it up to 0.011 solar mass.

...you already have a more efficient solution than a nova.

If an Alderaan-style annihilation is not enough to get rid of the larvae, a nova will very probably also not be enough; rather it will scatter the critters all over the Universe, which is exactly the opposite of what we need.

Rather, you place a seed missile next to the planet to be killed and "crank it up to 0.011 solar masses". Then you send it in a close orbit around the planet. Or rather the other way round, since 0.011 solar masses is about 3600 times the mass of the Earth. This is also massive enough that Hawking radiation is no longer a concern (black holes above the size of the Moon are stable).

Roche's limit does not apply to a black hole, but it does apply to the planet, which will be shattered into an accretion ring around the black hole. The radiation intensity alone should be enough to kill off the larvae. If it isn't, they'll be taken care of by spaghettification. And if even that is not enough, once they're past the event horizon they'll no longer matter.

Once locked by a Schwarzschild black hole, neither the planet nor the larvae have realistic possibilities of ever escaping. You get 100% clearance.


A K2 level civilization should be able to harness the power of their home star (or any star they control) and create a Nicoll-Dyson Beam. A very interesting video is here as well.

enter image description here

with enough energy, anything is possible

Essentially, you will be sending so much energy into the system planets will ablate away (which should solve your pest control problem) and the extra energy impacting the star will upset the rate of fusion reaction, triggering giant flares as a minimum, and possibly evaporating the outer surface of the star as well. Mad scientist Alexander Bolonkin even believes that adding extra energy to the star's outer layers could trigger a runaway fusion reaction, although the science is not....settled.

Outside of massive beam generators, the energy could be harnessed to deliver RKKV's. Even a very small mass moving at relativistic velocity can deliver massive amounts of energy. The Atomic Rockets "Boom Table" suggests you could generate 11kt of energy on impact with a single gram moving at .75 c, and 29kt if the same gram was accelerated to .9 c

enter image description here

man, that had to hurt

Sending a swarm of pellets moving at .9 c could cover the entire solar system and strike every planetary body, asteroid, comet and icy body that could conceivably hold an enemy object. Follow up swarms can be sent for good measure. And all that energy suddenly being deposited into the star will have similar effects to a Nicoll-Dyson beam weapon as well.


Plain and simple: tap enough dark matter into your microscopic black hole to turn it into a regular-sized black hole with typical lifetime comparable to lifetime of a universe and rely upon relativistic effects to confine larvae in the singularity indefinitely long.


Here is an idea: use a micro black hole to trigger an orbital instability in the planetary system. Planetary systems tend to form on the edge of stability, such that relatively small perturbations can destabilize them. What happens is this: small kicks change the planets' orbits and make them cross. In systems with just rocky planets, this would lead to giant collisions between the planets. Bad for any life on those planets.

enter image description here

In systems with gas giant planets, something like this animation can happen: https://youtu.be/gT2_3NcL8UM It's from a real N-body simulation I published a few years back; the inner colored bodies that are in the process of forming terrestrial planets all end up falling onto the star. The same would happen to any already-formed planets.

The basic idea is to use the mass in a black hole to trip up a planetary system to make it gravitationally self-destruct.

The upside: this is an efficient use of mass.

The downside: it can take time (like, thousands to millions of years) for the planets to be destroyed. Although if you planned it really precisely I imagine this could be sped up.


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