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Options for a Red Giant Future

Planetary engineering on the largest scale might one day reveal itself to us through the observation of a Dyson sphere or other vast object created by an advanced civilization. But it’s interesting to think about alternative strategies for using celestial energies, strategies that assume vast powers at the disposal of mankind as projected into the distant future. Thus an interesting proposal from the Swiss theorists M. Taube and W. Seifritz, who consider what to do about the Sun’s eventual evolution into a planet-swallowing red giant.

A Sunshade and a Planetary Shift

Considering the possibilities of preserving the Earth during the Sun’s transition into a brighter and much larger object, the authors discuss alternatives like raising the Earth’s orbit to a safer distance or using a parasol to shield the planet from its rays. That might tide us over for a few billion years beyond the point where an unprotected Earth could survive as a habitable place. But the paper only begins here. After the sunshade, the authors go on to discuss their plan to create an artificial sun in the Kuiper Belt, where an Earth slowly moved into an outer orbit by gravitational swing-by techniques can eventually find its new home in a stable orbit around a life-giving source of heat and light. Call it an ArtSun, as they do, and ponder how much science fiction it might inspire.

Imagine, for example, an Earth gradually being shifted to a new orbit over a period of perhaps tens of millions of years as the Sun begins its inexorable growth to engulf the inner planets. And imagine our world, as the authors do, illuminated for the duration of the journey by a ring of fusion power stations encircling the planet at an orbital distance of 350,000 kilometers. This ring of whatever materials are best suited for the job is inescapably reminiscent of Larry Niven’s Dyson-esque Ringworld, though on a much smaller scale, and suggests a level of planetary engineering as beyond our present capabilities as the Large Hadron Collider would have been beyond the imaginings of Greek philosophers.

Given the changes in technology that make even a thousand years from now a vista too remote to analyze, it’s hard to know what might have transpired in a billion years, much less the five billion the authors contemplate during which the parasol might shield the Earth, or the billions beyond that it could survive around the new star. But the question is worth pondering from the standpoint of SETI, I think, where we might think about what an advanced civilization might do given enough time and powerful enough tools. And Taube and Seifritz’ ArtSun is a marvelous creation in any case, made up of gas giants culled from other stars. Surely that would throw an interesting astronomical signature?

Creating Sol II

The idea here is that within twenty light years of the Solar System there ought to exist enough planetary systems with gas giants, many of them much larger than our own Jupiter, to cull for use in the new stellar creation. Here’s the plan:

Some hundreds of such ‘gas giants’ will be transported to the Kuiper Belt by means of the ‘swing-by’ technique and fused together to form an ‘ArtSun’ which will ignite when its mass passes over a certain value. Unmanned spacecraft under fully autonomous control will explore those planetary systems and will find the corresponding asteroids for the ‘swing-by’ technique to accelerate the suited ‘gas giants’ out of their planetary systems. DD-fusion will be the source of energy for all these enterprises whereby deuterium will be separated out from the atmosphere of the ‘gas giant’. Although we do not know how to ignite a DD-explosive reaction for a Dyson-like space ship without the help of fissionable material we proceed on the assumption that we will have found a method in the far future.

Coincidentally, Adam Crowl just sent me links to two papers by Friedwardt Winterberg discussing DD fusion — creating propulsion solely through the non-fission ignition of pure deuterium — and thus opening up manned exploration of the entire Solar System. But more on this another day, because I’m not ready to leave Taube and Seifritz without a few more details about creating new stars. The duo discuss fusing twenty imported gas giants to create an M-class star, with the potential of using up to 100 such planets to create a G5 star not so different from the Sun. The M-dwarf would seem to be easier but a bit more problematic:

Under the assumption we let rotate Earth around such a Red Dwarf illuminated with the same ‘solar constant’ as today, we find a sidereal period for Earth being only 6.91% of a year, i.e. only 25.2 days but the not yet answered question is whether the photosynthesis will work satisfactorily under the red light.

Yes, and we’d best keep photosynthesis fully operational. On the other hand, an M-dwarf offers a tremendously increased lifetime over a G-class star. The authors go on to consider how to power up the fusion devices that will keep the Earth illuminated during its long orbit-shifting journey to 50 AU. All the deuterium to run these and the planet-shifting operations around other stars will come from a familiar source (familiar, at least, if you know the history of Project Daedalus, the British Interplanetary Society’s starship design) — the atmosphere of Jupiter and perhaps Saturn. Given the future technologies we’re discussing here, mining outer system atmospheres for fuel would doubtless be a trivial operation.

Moving a Planet, or Moving Off-Planet?

Would an advanced civilization ever embark on such a task? If it did, would the astronomical signature of planetary re-location be something today’s astronomers in our own Solar System could flag as the likely sign of extraterrestrial engineering? My own guess, from a parochial 21st Century perspective, is that a civilization with the ability to travel to another solar system to move a gas giant to ours probably has the ability to consider massive re-location of population as needed to the nearest available habitable planet, or indeed, moving into vast space-based habitats that could survive a red giant’s depredations.

The authors choose planetary migration because they believe only a small number of Earth’s inhabitants could be evacuated via the creation of a starship. But their model is Freeman Dyson’s upgraded Project Orion vehicle from a classic 1968 paper, one that would carry a 10,000 ton payload at 10,000 kilometers per second via Orion-like nuclear bomb detonations. It’s hard to believe that a civilization that might survive billions of years into the future would be limited by 1968 starship design (a design that Dyson himself later gave up on as being unworkable). If anyone is around in five billion years, protected by Taube and Seifritz’ sunshade and hoping to avoid a swelling Sun, I think they’ll be opting for interstellar transport away from a soon to be devastated Earth.

But it’s fascinating to speculate on alternatives. Take a look at the discussion of planetary orbit changing using asteroid swing-bys, and ponder the risks of setting a large asteroid on a near-miss trajectory that, given the slightest mistake, could end all life on the planet anyway. One thing you can say about Taube and Seifritz — they’re not at all afraid to think big. And it’s worth your time looking this one up for the imaginative tinkering with the future that gets us thinking ultra-long-term, not to mention prompting those good SF story ideas. The paper is Taube and Seifritz, “The search for a strategy for mankind to survive the solar Red Giant catastrophe,” available online. That Dyson paper, by the way, is “Interstellar transport,” Physics Today 21, (October, 1968), pp. 41-45. And have a look at Crowlspace for other options for red giant survival.

Comments on this entry are closed.

  • andy December 3, 2008, 17:44

    Even if we do all this fancy planetary pinball, there’s still have the problem of the geophysics conspiring to kill the Earth: cooling of the interior puts the magnetic field and the plate tectonics under threat. Nothing’s replenishing the Earth’s slowly decaying inventory of radioactive material. Even if you replace the radioactives with tidal heating by putting the Earth into an eccentric orbit around a gas giant (and then you’d have to maintain that orbital eccentricity against tidal circularisation), you’ve still got to deal with the production of non-subductable continental crust which could cause tectonics to seize up anyway.

    Meanwhile, the ability to move gas giants around at will leads to some aesthetically-interesting possibilities: for starters, how about a system with three gas giants in the habitable zone (the less massive two in the Trojan points of the most massive one), each with a system of multiple Earthlike moons?

  • Colin Weaver December 3, 2008, 21:43

    This article brings up a couple of questions for me:

    1. If it is feasible to move Earth while supporting life via a ring of fusion plants, why go to the trouble of moving a bunch of Jovians to the remains of Sol system? Wouldn’t it be better to just support the Earth for the millions of years needed to move it to a suitable M class system.

    2. If sufficient Jovians can be “harvested” to build an M5 star, why go to the trouble of making a star which will radiate most of its energy into interstellar space? Why not just keep the ring of fusion power plants around the Earth and use your Jovians as a fuel supply, thereby wasting much less energy and obtaining several of orders of magnitude more life span? If we take the approach of harvesting Jovians directly, billions of years of additional energy should be available just from the gas giants in our own system.

    I’m assuming that any society advanced enough to consider moving the Earth, or building its own stars, will have technology able to keep the Earth’s geology & biosphere running for as long as energy is available. I’m also assuming that any problems with the different spectrum of an M5 primary will be dealt with either by genetic engineering of the plant life, or by collecting solar power and re-radiating with a spectrum more like a G class star.

    I think we can discount any idea of building more G class stars, except possibly for artistic purposes. It may be viable to move the Earth to new G stars while they continue to be born for the next hundred billion or so years. But, building an artificial star of much over 30% of Sol mass, strikes me as wasteful and unlikely to be considered by an advanced society other than for aesthetic purposes.


  • Adam December 4, 2008, 0:27

    Good point Colin. Unless Earth is only one planet amongst many at that late stage that its inhabitants will want preserved. With all the mass available in the system several more Earths could be made and orbitted around Jupiter or Saturn or in some kind of multi-planet ring around the Sun. If the inhabitants so desired both Jupiter and Saturn could be converted into habitable planets via fusing their atmospheres into more useful elements, and probably deconstructing them for bulk mass. In 5.5 billion years there’s time enough to do any of a hundred different scenarios and utterly remake the Solar System.

    Some scenarios of planet formation mean there’s about 35 Earth masses of “small” bodies unaccounted for this side of the Oort Cloud – imagine thousands of Triton sized bodies, or hundreds of Mars. All will want to have a say in how best to survive the Sun’s evolution.

  • David December 4, 2008, 1:02

    This is fun.Newton had a picture of an orbiting cannonball in Principia Did he see that in 300 years we would be sending spacecraft out of the Solar system?
    If you want ultimate you still cant beat Tipler colonizing the whole universe by consuming the dark energy –

    But back to the present I really fear we may need the sunshade sooner rather than later

  • Benjamin December 4, 2008, 1:14

    What would worry me most is the effect of throwing Jupiter-sized chunks of mass at great velocity into the Solar System – not because I’m afraid you’d hit anything, but because you would have to deal with the chaotic dynamics of the orbits – especially if you’re doing this in the outer solar system, further from the sun’s gravitational well.

    I’d hesitate to do this for fear that you’d end up irreversibly changing the orbits of the outer planets, asteroid belt, even more; an infinitesimally small error could, in theory, lead to drastically different results, and doing this a hundred times is a scary thought.

    I’m also somewhat skeptical about the advanced technologies posited for large, manned interstellar journeys: I’ll grant you arbitrarily good materials from nanotech, I’ll grant you DD-fusion, but energy is something you simply can’t get around. For the energy cost of such a population relocation to another system, let alone the cost of terraforming, I don’t doubt that you could construct an enormously more satisfactory habitat in our solar system.

    If we’re talking about really, really deep time, where there isn’t any usable energy in the solar system – if the sun is dead – then, and only then, does the idea of making a second sun seem sensible – but I’d still ship out to another solar system and save myself the effort. In that case I wouldn’t expect to be a biological human – if anyone’s read Diaspora by Greg Egan, the Gleisner robots and the polises seem more sensible.

  • Darren Williams December 4, 2008, 6:47

    I think things need to be put in a sharper contrast, to see how even seemingly visionary ideas can be primitive to the super-science of a profoundly more advanced species.

    In the five billion years you mentioned that the authors envisage, the evolutionary distance between us and them is, quite literally, greater than the time it took terrestrial single celled organisms to evolve into us.

    What might such a civilization – as removed from us as we are from an amoeba – what might they be capable of?

    You may answer that they would still be constrained by the laws of physics – maybe so, but our understanding of quantum and relativistic physics is, to put it very mildly indeed, incomplete.

    As with any field of science, in astrophysics, we don’t know what we don’t know.

    I haven’t read the paper yet (just going by what this post says) but I think another possibility might not have been considered?

    Our distant successors may find a may to rejuvenate the nuclear fuel of our own sun, bringing it back on to the main line of a yellow dwarf again, without the need to move our planet. Knowing that this is coming millions of years before it is even a remote threat, means that this could even be a slow process.

    The same applies to Andy’s comment about interior cooling.

    But, why bother, if we could indeed move elsewhere? Millions or even billions of years from now, we may well be spread across the galaxy with no need to preserve our world. But we may still do it.

    Why? Well, I think it may still be human nature, no matter how changed we may be. Earth is our cradle. Our sun gave us life. Perhaps it’ll be the sentimentality of preserving the motherworld, the place that gave birth to us.

    If by then, we have evolved into something that no longer loves its mother, then perhaps we won’t deserve to survive anyway.

    While this would be an enormous undertaking, you can’t even use the analogy of what the channel tunnel project would seem to a cave man, because, again, even a billion year old civilisation may be able to do things that many today might consider the province of the gods.

  • James M. Essig December 4, 2008, 12:08

    Hi Paul;

    This is a most excellent article and a fascinating topic.

    One can imagine a very massive space ship with powerful fusion rockets whose net thrust induces the craft to pull the gas giant planets forward, a sort of gravitational tractor beam. The fusion rocket thrust could be directed away from the planet being towed so that the rocket exaust stream does not degrade or wipe away the planets atmosphere.

    Assuming that such a planet might have a mass of 2 x 10 EXP 24 metric tons and that it is desired to impart a motion to the planet of 100 kilometers/second, the total energy imparted to the planet to bring it up to speed would need to be the equivalent of (2 x 10 EXP 24)(10 EXP 3) metric tons of TNT or 2 x 10 EXP 27 metric tons of TNT. The best fusion fuels yeild about 175 megatons per metric ton of fuel, and taking into account ineficiencies in the rocket thrust mechanism, we can assume that each ton of DD fuel has an effective yield of 100 megatons. Thus, the amount of fuel required to accelerate the planet to 100 kilometers/second would be (2 x 10 EXP 27)/(10 EXP 8) metric tons or (2 x 10 EXP 19) metric tons of DD fuel assuming 80 percent or greater rocket thrust to planet kinetic energy conversion efficiency. This is roughly equivalent to the mass of the Earth’s moon. This seems highly doable for a several billion year old civilization.

    Regarding photosynthesis using red light, from a Red Dwarf, I have read in a recent issue of Popular Science Magazine that lettuce grows most efficiently under red light (of a certain frequency).



  • Ronald December 4, 2008, 12:20

    I don’t like to use the word ‘ridiculous’ for people’s brain-children, but in this case I find it hard to avoid.
    I agree with the previous commentors (andy, Colin) and with what Paul is saying.

    It all boils down to the same basic thing: certain things will most probably never be done, even if theoretically possible, because they are so terribly inefficient and/or ineffective.

    It would always be *vastly* easier and cheaper (in terms of energy expenditure and otherwise) to settle and, where necessary and fesaible, terraform planets near other stars than to perform the outlandish proposals by Taube and Seifritz.

    Furthermore, if you really want to create a more or less sunlike star, such as the proposed G5 star, from something different but common, it would probably be a lot better to start with a M dwarf and bombard that with the mentioned gas giants. Or even better: merge two M dwarfs, that are already in a close binary.
    If anything like it, I could imagine a (distant) future or an (very) advanced civilization re-engineering unsuitable stars into more suitable ones: ‘astraforming’.

  • Alexander December 4, 2008, 16:10

    Although I’ve read that it would be easier to stream gases back to the solar system than to send humans out in colony ships. This makes sense at first glance—after all, sending gas through space seems a lot easier than sending a bunch of people in an artificial environment, though who knows just what we’d be capable of (or be) in a few billion years’ time. Those were more near-scale (less than a millennium) speculations though, and by the time the sun turns into a red giant I’d hope that humanity/humanity’s successor is able to do both.

    Even though ArtSun stands for “artificial sun,” I could also stand for “art sun”—I feel like there’s a great aesthetic impulse in this work, and in the speculations it’s inspired (I particularly liked imagining andy’s three gas giants with earth-like moons). It’s the sublime on a scale that rarely has been thought of before.

    David’s also right about needing the sunshade sooner rather than later—even if we can get global warming under control, the sun’s still going to be warming over the next few hundred million years.

  • tacitus December 4, 2008, 16:57

    First, excellent comments from Colin.

    Second, if humanity is around in a million years, let alone a billion, then we will have almost certainly have spread out through a good portion of the Milky Way by then, inhabiting perhaps hundreds of different worlds and artificial habitats in dozens of different solar systems.

    Earth will still be important has our original home world, sure, but after a million years, what’s the difference between having a recorded history 1 million years long, and one which is, say, 980,000 years long, which is what other human settlements on other worlds will likely have by then?

    Once the Earth is finally in danger of being consumed by the Sun, I can certainly see the possibility that an “Earth Preservation Society” might undertake the task of moving it out of harm’s way. I would agree, however, that creating whole new sun in the same system seems a little excessive. A combination of artificial suns (i.e. humungous spotlights) in orbit around Earth along with the relocation of the planet to the nearest stable G-class star is probably the most you can expect, though it would be even more efficient simply to transfer the surface features deemed worth saving — monuments, cities, even regions — from one planet to another.

    99.9% of what makes up the Earth — i.e. below the surface — is just plain old boring rock (molten and solid) and of no interest to anyone.

  • tacitus December 4, 2008, 17:13

    Iain M. Banks’ Culture novels are set in the far distant future of humanity, at a time when there are virtually no limits to the resources available — i.e. there is enough for everyone to have what they want without having to fight to get it.

    As a result the Culture is a decadent place, where most things imaginable are available at a mere whim. One such whim is living space, and while inhabitable planets remain a finite resource, the construction of artificial living spaces is not. Thus massive, constructed habitats populate the Culture universe, configured into all kinds of shapes and sizes at the whim of their designers. Cities of glass, hundred mile high waterfalls, floating castles — you name it, if the technology allows it, it’s yours.

    I suspect something like this is in the future of a successful human civilization — certainly on the million year long timeframe (if we haven’t all become post-human AIs inhabiting our own virtual worlds by then, of course). As for living on planets? How passé!

  • Colin Weaver December 4, 2008, 21:33

    To my previous comments, I’d add that assuming we survive the immediate challenges we’re facing, I hardly expect us to be stuck with anything so prosaic as carbon based biology and the need to farm plants and animals under a warm yellow sun.

    By the time time the sun starts moving off the main sequence, our post-human remote descendants are unlikely to be resemble us. Consequently, imagining deep future scenarios where we attempt to preserve the Earth as it is now is almost certainly an exercise in irrelevance.

    The true challenges facing us are the diaspora of our descendants across the entire universe, and then survival far into the heat death.

    But first, we have to avoid extinction within the next thousand or so years, or worse still the trap of a post-technological society stuck on a resource depleted world.


  • Didac December 5, 2008, 6:25

    Colin Weaver is right. If we are to “survive” in the next few thousands of years, we need impressive changes both in technology and social management. However, preserving the Earth both from internal changes (andy) and Sun “degeneration”, although of no practical use for our hypothetical post-trans-post-transhuman descendants, may be defended for the same reason we preserve ruins from Rome or Athens (i.e. tourism).

  • andy December 5, 2008, 8:02

    You may answer that they would still be constrained by the laws of physics – maybe so, but our understanding of quantum and relativistic physics is, to put it very mildly indeed, incomplete.

    Yes, I totally agree that our lack of a complete theory of everything means that in the future all have magic pixie dust so we never need to worry about conservation of energy and momentum or tedious distractions like the second law of thermodynamics while we’re larking around the cosmos like gods.

  • hiro December 5, 2008, 15:35

    I assume that we can do everything to save the Earth and its environment in the next trillion years. However, nothing can last forever, I just wonder what we will do when the time-scale is 10^33 years or beyond, does anyone still try to save something in that far distance period of time?

  • James M. Essig December 5, 2008, 18:24

    Hi hiro;

    It is interesting to speculate on what we might do to survive on the time scale of 10 EXP 33 years. 10 EXP 33 years is only a few orders of magnitude removed from the least lower experimentally determined bounding value for proton decay.

    Eventually, CMBR capture mechanisms may be needed to power accelerators to produce protons by particle collsions. The CMBR by that time will have a super low frequency, and so perhaps some sort of grid that collects the background radiation by magnetic induction may be required.

    If humans ever want the opportuinity to time travel 10 EXP 33, or perhaps even 10 EXP 100 years into the future, maintaining a stable orbit around an ultra massive black hole just outside of the blackholes photosphere at extremely high gamma factors might permit such time travel into the future when coupled with proton, neutron, and electron generation and collection mechanisms in order to maintain the structure of the orbiting satelites and the crew menbers bodies.

    Note ultra massive blackholes are a new taxonomic class of blackholes recently proposed to exist with a mass of between about 13 billion solar masses to 60 billion solar masses and perhaps greater. Also, note that as long as the rate of power capture by the blackholes, of background radiation, other photon, and massive particles , etc, is greater than the power radiated by the blackholes in the form of Hawking radiation, the black holes will continue to grow.

    I had a strange idea just now as I was composing these comments to the effect that perhaps blackholes beyond a certain size limit will continue to grow for eternity if the rate of general zero point virtual particle capture or zero point energy capture becomes greater than the rate of Hawking Radiation release by the zero point particle pair production mechanism responsible for Hawking Radiation. Thus, the net energy outflow rate of blackholes based on the interaction of such blackholes with the zero point virtual particle fields may be more complex than simply the existence of a Hawking Radiation term. There may be other mechanisms such as net energy influx wherein the term(s) of the(se) mechanism(s) become dominant for stupedously massive blackholes.

    Regardless of how we prolong human civilization, perhaps into physical eternity, the mere fact that we at Tau Zero, especially all of the contibutors of this thread, are intellegibly discussing the duration of the human race into cosmically remote future epochs, and defining some of the technological issues and problems needed to be overcome for a perpetual human civilization gives me great hope. Afterall, we have been a technologically advanced civilization for only about 1 1/2 centuries and the fact that very high quality forums such as Tau Zero are spawing such contributions gives one hope in what we humans can accomplish in a trillion years, perhaps even in 10 EXP 33 years.



  • Bryan Derksen December 6, 2008, 14:19

    I don’t imagine there’ll be any practical need to “save” Earth in the far distant future, aside from perhaps some sort of nostalgia or religious reason or whatnot that’s impossible to predict. Assuming humanity develops significant space travel and colonization capabilities most of us would probably be living in artificial habitats elsewhere in the solar system. Possibly we’d have already taken Earth apart for raw materials by then. Our descendants that far down the road might not even be organic.

    But still, there’s an alternative method for managing the Sun’s evolution into a red giant that provides other inherent benefits; “mining” it for materials and reducing its mass via star lifting (http://en.wikipedia.org/wiki/Star_lifting). If we were to pull off enough of the Sun’s outer envelope in a controlled manner it would lengthen the period where Earth remains in a habitable zone. And if you’re really a fan of building new stars you could get plenty of long-lasting M dwarfs out of the excess hydrogen and helium you’d wind up with.

  • Ronald December 8, 2008, 7:20

    Further to my previous comment about ‘astraforming’: a significant proportion of double and triple star systems consist of M dwarfs and late K stars (i.e. red and orange-red dwarfs), some of them being very close components. Dim, but very long-lived.

    One could imagine that these could theoretically function as a kind of ‘solar reserve’ for a very advanced (Kardashev III) civilization in a very distant future (when the universe is roughly on the order of 100 gy): spare stars to be merged into new solar type stars, as the galaxies are running out of natural solar type stars (F, G, early K). Since total brightness (energy output) relates to the triple (cubed) power of mass, two early M stars, or three later M stars, or an M star and a (late) K star, could create a sunlike star.

    Provided, of course, that mentioned civilization would still have a need for solar type stars. This is often being questioned, also here, but, as I believe, injustified.
    First of all, because an advanced civilization at 100 gy of age of the universe would not necessarily be nearly as old itself (this would even be extremely unlikely), on the contrary, might well be a (relatively speaking) very recent appearance in the cosmos, still having the basic needs (or chosen pathways) of carbon-based life, water and sunlight.
    Secondly, because precisely an advanced civilization might be expected to have moved beyond merely spending its energy on survival and self-perpetuation and instead occupying itself with the more creative and estethic sides of life, such as spreading life and beauty across the cosmos.

  • ljk December 10, 2008, 1:06

    Ten Ways the World Could End

    CBC Dec. 6, 2008


    Nine prominent Canadian scientists and one science fiction writer were asked to imagine how they think the world might end….


  • andy December 13, 2008, 14:14

    Regarding the kinds of planets that could be habitable when their star goes red giant, see Habitability of Super-Earth Planets around Other Suns: Models including Red Giant Branch Evolution by von Bloh et al, which considers geological factors. The habitability of Earth-mass planets is expected to end at 6.5 Gyr even for optimal placement in the habitable zone. The best bet is a massive water world.

  • Dmetros Yatsenko February 5, 2009, 22:49

    I think it would be much easier for us to just move to another planetary system, rather than steal planets from other stars to have them migrate to our own system to create a star. That just sounds unrealistic. And of course, we cannot live in the Solar System forever. Our Earth is likely to be knocked out of orbit by the masses of gas cast off by the dead Sun (planetary nebula), though I’m not ceratin about that. If our Sun was bigger, the supernova explosion would undoubtly blast all the planets out of the system. I would not recommend landing on a planet in orbit around a blue giant, even if the planet’s surface temperature is just right. Primary life would not be able to evolve on such a planet because a blue giant lives too little. And if we populate such a planet and live there until the blue giant explodes, it would be too late. Earth and its Moon (if the pair won’t get separated) would turn into rogue planets. If we try to alter Earth’s trajectory slightly, this will change it entirely. The Earth would be orbiting another star at the right distance, if we calculate how to alter its path. The easiest way is just to leave Earth, of course bringing all of its life with us, and go in spaceships to another planetary system. If there are no terrestrial planets, then the potential moons of giant planets can do for us to live on them. I am especially exited about finding extrasolar dwarf planets and moons. For the first time we would see other Solar Systems as clearly as our own! I can’t believe that we still did not find any aliens! It seems impossible – only one small planet in an entire universe has life?!