In my story, I have a fairly advanced human race who is at the point they want to start terraforming planets. Of course, all of the materials necessary have to come from somewhere, and the proposed solution is simple. In solar systems devoid of life and livable planets, mine the sun for use in atmospheres and planets for increasing the mass of other ones.

One thing I noted would be that the sun is made up of mostly hydrogen and helium, so while a sun would provide a good amount of hydrogen, it wouldn't work very well for other atmospheric components (as in more fusion would be required to produce a reasonable amount of oxygen or carbon).

My question is how technologically advanced would a civilization have to be to do this? What would be some of the difficulties facing this method? If this isn't really feasible, is there another way to find atmospheric components and water for terraforming?

  • $\begingroup$ Actually there's just 1 star which is called Sun, the other one (it's illegitimate twin) is called Nemesis was nowhere to be found! $\endgroup$
    – user6760
    Dec 25, 2016 at 1:39
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    $\begingroup$ @user6760: Uncounted SF stories, and much else, say you're wrong. If you're on a planet that orbits a star (or several stars) then that star is the planet's sun. $\endgroup$
    – jamesqf
    Dec 25, 2016 at 3:40
  • $\begingroup$ @user6760 Sorry, but I don't think I get your joke. $\endgroup$ Dec 25, 2016 at 3:45
  • $\begingroup$ Hi merry xmas BTW I wasn't joking. $\endgroup$
    – user6760
    Dec 25, 2016 at 4:02
  • $\begingroup$ @user6760 Then what is that stuff about an illegitimate twin? $\endgroup$ Dec 25, 2016 at 4:06

6 Answers 6


Gas giants are cheaper and require less handwaving

  • Stars are made of plasma. If you harvest the material from the outer layers of a star - or even from ejected matter - you will need a way to cool it down. Space is devoid of the gases needed to move this heat elsewhere, so it will require enormous space radiators. This is very, very inefficient. Meanwhile, gas giants are composed of gas and small particles! No large-scale cooling necessary.
  • Stars have more gravity. It takes much more work to orbit a star safely than it does to orbit a gas giant. For large-scale loads of matter, you will want to save energy.
  • Stars are hot. Unless you use an unfathomably large magnetic field to move the plasma toward your ships (which would require so much energy that the magnets would melt), you will want to come in contact with the surface of the sun in some way. For reference, the surface of the sun is 5,777 K, while iron vaporizes at 3135 K: without handwavium, it's extremely difficult to collect any material.
  • Stars have the wrong compositions. While gas giants may mostly be made of hydrogen and helium, they are theorized to have solid cores of more useful elements. In addition, stars have significantly more internal pressure - that will crush even the strongest apparatus. They literally function by ripping apart and smashing together subatomic particles - there is no plausible way to put anything deep into a star to harvest useful elements.

Even if you opt to fuse hydrogen to make heavier elements (as opposed to mining them) it is easier to acquire that hydrogen from gas giants. It's easiest to opt for the cheaper option.

To mine a sun

You need to have the energy to escape a star's gravity at virtually any distance; to construct materials impervious to heat that will normally turn any element into a plasma and tear it to shreds; to withstand some of the most extreme pressures in existance; and to cool a plasma to a gas en masse. Sounds like a Kardashev 2.9

To mine a gas giant

You need to have the energy to escape the mass of a gas giant; to siphon gas in large quantities and transport it, and to withstand a fraction of the pressure that a star would contain. Sounds relatively close to a Kardashev 2.

  • 1
    $\begingroup$ Surely you don't think that "mining the sun" involves building physical objects which enter the sun and move matter out with pipes, right? Right? See the video linked in Thucydides' answer. By definition, the Kardashev scale is a measure of size, not technology level. Since a Kardashev 2 civilisation can harvest the entire energy of its parent star, it is, by definition, already past the point where it cares about mining gas giants for raw materials. Basic star lifting is a considerably smaller scale project than getting to a full Kardashev 2 energy consumption. $\endgroup$
    – Yurgen
    Dec 25, 2016 at 11:28
  • $\begingroup$ @Yurgen Being able to build a giant sphere out of solar panels does not translate to "not caring about mining gas giants" but "only caring about stars" in any way shape or form! Even if they have the power to do both, which is incredibly difficult to achieve, gas giants are significantly cheaper and will always remain so. $\endgroup$
    – Zxyrra
    Dec 25, 2016 at 13:32
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    $\begingroup$ Jupiter, the largest gas giant in our solar system, has about 0.1% of the mass of the Sun. To claim that it will always remain cheaper than extracting mass from the Sun is taking a very short-sighted view of things. Jupiter will be mined out long before any significant change in the mass of the Sun is achieved. Furthermore, the methods of extracting matter from the Sun use solar energy to do so. Do you have calculations to show that the additional cost of transporting that energy to Jupiter are less than the savings from a shallower gravity well? $\endgroup$
    – Yurgen
    Dec 25, 2016 at 15:34
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    $\begingroup$ Um, just wait? Space is cold and the Sun's photosphere is an incredibly rarified gas by atmospheric standards. Some rough calculations (hyperphysics.phy-astr.gsu.edu/hbase/thermo/cootime.html#c2) suggest that a thousand-kilometre column (tiny, by astroengineering standards) can support a mass flow rate of over a billion tons per hour and still passively cool the plasma to room temperature. I didn't say "not pump". Stop putting words into my mouth. I said "not pipe". As in, not dropping a metal pipe into the Sun and trying to suck stuff up it, because that would be stupid. $\endgroup$
    – Yurgen
    Dec 25, 2016 at 17:12
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    $\begingroup$ You also seem to have a strange idea of how magnets work. If you're using superconducting magnets, (almost) no work is done by the magnets on the plasma, and no work is done by the plasma on the magnets. All the energy for extraction is supplied by the reflectors. Tokamaks wouldn't be a thing if curving charged particles with magnets inherently transferred energy between them. $\endgroup$
    – Yurgen
    Dec 25, 2016 at 17:32

The technology to take matter from a star is called Star Lifting, and it is a feat of mega engineering which allows the engineers to take plasma from a star and store it or move it for use elsewhere.

As has been noted in other answers, the primary results of Star Lifting is the accumulation of large quantities of hydrogen and helium, which isn't directly useful in terraforming. You could use nuclear fusion to transmute the elements into heavier elements, and generate lots of energy at the same time, but perhaps a better potential use is to move planets around the solar system.

The plasma, as it radiates away its energy and cools, should be collected and stored. The best way to do so is simply pump it into a small area until self gravitation takes over and you build small "gas giant" planets about the size of Uranus or Neptune.

Now we already understand that planets can be moved over long periods of time through the mechanism of momentum exchange. Spacecraft do this routinely, slingshotting past Jupiter and picking up speed, while Jupiter loses exactly the same amount of energy. IT would take millions of spacecraft dong moment um exchange with Jupiter for millions of years before we see any appreciable change in Jupiter's orbit, and it is possible that Earth could be moved more quickly transferring momentum between Earth and millions of asteroid flypasts. Paul Birch proposed moving Venus or Mars even more quickly by making a stream of extremely high energy projectiles rounding the Sun and transferring their momentum to the planet in question.

An artificial Uranus sized planet created in the right place could do the same thing far more quickly, transferring orbital energy to the planet being terraformed in one pass due to the much greater amount of mass and changing the terraformed planet's orbit so it travels towards the centre of the "Goldilocks zone". With the planet in the right part of the zone, creating a liquid hydrosphere becomes much easier, and terraforming can proceed with one of the largest issues solved. The artificial gas giant might have to be placed in an eccentric elliptical orbit to prevent it from closing with the terraformed planet until just the right time, so the engineers will need to plan and calculate this long in advance of the actual movement taking place.


The funny part of them all is the following - The Universe is made mostly of Hydrogen and Helium, Abundance in the Universe of the elements, but we still have planets and expect them to be not only in our star system.

The question is not how low is a percentage of elements we need, but how big is the thing where they are. The Sun, Sun Fact Sheet, is relatively big, 333'000 times mass of the Earth.

Photosphere Composition:
Major elements: H - 90.965%, He - 8.889%
Minor elements (ppm): O - 774, C - 330, Ne - 112, N - 102, Fe - 43, Mg - 35, Si - 32, S - 15

In fact, sun composition contains more than just 330ppm of carbon, but this concentration is on top of the sun, in upper layers (carbon is relatively heavy and it sinks to the core, but still some of it floats in upper layers).

This concentration is relatively big actually, it is 0.396% by mass, so to made one planet like Earth but made of pure carbon, you need to purify matter of about 250 mass of earth from upper layers of the sun. As a byproduct, you will get about 2 earth mass planets made of oxygen, about half mass pure neon planet, 0.6 mass from Fe etc.

If you combine those 2 oxygen planets with a proper amount of hydrogen - you will get about 2+ planets made of pure water.

And that all can be done just by barely scratching the sun, all you need it 0.1% of the sun.

Gas giants like in our system (we are lucky to have cold ones) are basically a small fragment of the star, and they have very similar composition.
Jupiter(Jupiter Fact Sheet), as an example, have the mass about 317.83 of the Earth, so basically it is a bit more than 250 masses you need to create a few planets made of pure elements.

In my the longest answer on WB.SE I began to describe the initial phase of the process, but answer limitation had effectively prevented to disclose all the details about the process. But it has some description how it can be done.

The main point is that to lift the matter from the star, you need a lot of energy, even by having all the energy of the star, but any matter which orbits the sun, may be effectively exchanged with the matter from the sun, because it already have all needed energy you may need to lift the matter from the star into the orbit around the star. Namely, it means all mass of the Jupiter(its hydrogen and helium) may be exchanged to heavier elements from the sun, and it will be enough to make about 300 planets like the earth.

But as you talking about tuning of a planet, you probably do not need the same scale of operation as in my longest answer on WB.SE

Water is not a problem at all because rocks are oxides of mostly silica, so any rocky planet can be made an ocean planet with the proper amount of hydrogen reacting with those rocks. (you better have space lift or space ring for that types of reaction, to not overheat the planet, and do the reaction in space). It may be a hardcore way of doing it, as there is a lot of water in asteroids, and it is guaranteed a lot of water in any system as Oxygen and Hydrogen are most abundant elements, and freezing point of water is pretty high. Water will form during the system formation and there will be a lot of water ice in a typical system(nearby supernovae blast may change the thing, not in favor of water ices but you always may go the hard way, making it from rocks and hydrogen from a star or gas giant).

Basically, all problems from your answer do not need - super intergalactic civilizations, elements transmutations, etc.

Would we have manufacturing in space and the wish to do so, we could do it ourselves, with technologies we already have. Maybe not from the sun but from gas giants for sure, with the sun we need a bit more advanced technology.

But really, you do not need terraforming's, build space habitats they are more efficient.


A civilization capable of this would have to be a Level 2 civilization (intergalactic), so I doubt that converting stellar-mass into heavier elements through fusion would be a problem for them. In fact, they may probably already be using fusion as an energy source, so the effort may be partially self-sustaining. Using their possible transporter tech (particle entanglement-based), they could actually "beam" the matter directly into the vicinity of the planet. Because of its density, it couldn't be too close, or maybe more than a few hundred tons at a time, too prevent massive decompression-based explosions from making the planet unlivable. Artificial magnetic fields to direct the plasma would also be useful to control the dispersion, as it will initially exist as high-energy plasma. If they're not quite this advanced, they can go about it the more conventional way and use flora and fauna from their home planets that can survive in the new environment initially, such as using plants to convert CO2 to O2 or bacteria to break down hydrogen sulfide to release oxygen. The drawback to this is that it takes a long time, as does enriching a planet through breaking down small asteroids and transporting them to a planets surface without causing a meteor shower.


The purpose is not to get hydrogen or helium, but heavy metals, which are only produced in stellar cores.

This was a feature of the astonishing Quantum Thief Trilogy written by real-life mathematical physicist Hannu Rajaneimi.

In Rajaneimi's book, it required only a the technology of a post-singularity civilization, still restricted to our own solar system. (The idea is that the mechanics are well within the bounds of a civilization approaching Type II on the Kardashev scale.


you mean star lifting?


this is not a common sci-fi device ,mainly because you would need to already have fusion and if you need hidrogen you can get away easier in jupiter and the asteroid belt and have ridiculously advance technology ,but it is possible

  • $\begingroup$ Hi, as links can get outdated occasionally, it's a good idea to explain what it is that the link is talking about in your answer, so would you be able to edit your answer to explain what starlifting is and why this answers the question (if it's not obvious from the explanation)? Thanks $\endgroup$ Aug 11, 2017 at 18:42

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