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One of the defining moments in the book and film 2001 A Space Oddesey is when Jupiter is converted into a star, thus bringing its various moons into play as habitable worlds.

Arthur C Clarke was a great author and researched deeply to know what he was writing about to make it realistic, but it was written a long time ago now, and our knowledge of astronomy and physics has evolved enormously since then.

I know (as did Clarke) that Jupiter is much too small to be a star, and will need the help of the monoliths (or some other plot device) adding mass in order to achieve fusion. I'm fine with that as a fictional necessity to achieve the goal, but I'm concerned that the end result wouldn't be as good for creating new real-estate as Clarke made it out to be.

So my question is: Does the basic idea of igniting Jupiter into a mini star still hold up, given our more modern understanding of physics? What did Clarke miss or simply not know about that would make this idea a non-starter? What would the effects be on Earth? And would the Jovian moons really become habitable?

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marked as duplicate by a CVn, Simba, sphennings, Frostfyre, L.Dutch Aug 11 '17 at 12:21

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Idea #1 (doesn't work)

The Jupiter can't be a star, because it requires at least around 70 Jupiter masses, hidrogen to burn. Below that, there is not enough pressure and temperature in the stellar core to start fusion.

Idea #2 (doesn't work)

But, there is always a "nearest" thing, a "most reasonable" thing what seems to most realistic.

The first idea would be to use some different isotope. The best fusable isotope is Deuterium. On some estimations, a star purely from deuterium could be as small as only 13 Jupiter masses.

Unfortunately,

  • it is still too high
  • Jupiter contains only a negligible Deuterium
  • which is a quite rare thing in the Universe, even because it fuses so easily. The few deuterium produced by different stellar processes, fuses quickly further to Helium.

Thus, also this idea fails.

So, the simple "just ignite it" solution from Clarke doesn't work.

Idea #3 (maybe... once)

enter image description here

What could work: most of the Jupiter mass is still hidrogen, which is fusable. Not easily, but it can. The hardest thing in the fusion is to "ignite" hidrogen into deuterium. Deuterium fuses (in multiple steps) to Helium4 already much quicker.

The current fusion projects try to ignite deuterium and tritium, even this seems very hard, but possible in industrial size. Likely it will be possible also with pure deuterium, although it would require probably larger reactors (to make it effective).

After that, there will be yet another, very big step needed: the way to fuse hidrogen. Just as comparison, in the Sun, a protons wait around a billion years to ignite to deuterium. After that, the deuterium nuclei fuse in seconds to helium.

On the current technology, fusing hidrogen would require probably fusion reactors not in the size of ten meters, rather in km size. Alternatively, some accelerator-driven solution could work.

Thus, the proposal is:

  • Building very large, km-sized baloon cities to fly in the upper athmosphere of the Jupiter and contain the km-sized reactors.
  • Build from them a lot.
  • They should heat the Jupiter athmosphere to a reasonable temperature (for example, 500C would be already enough to give heat to te Jupiter moons).

Of course, no humanity will ever build so many machines. Likely their mass would be many million times of the current, yearly steel production of the Earth.

But, our current industry doesn't use very heavily robots. Maybe these reactors could be once built by large, automatized robotic factories on the moons of the Jupiter.

Also the robotic factories could be built by robots.

Idea #4 (it could work, but it is a very different solution)

Large (planetary size) solar sail could be used to reflect the heat of the Sun to the Jupiter, or more easily, to the Moons of the Jupiter. This image does it with our Moon, but the idea is the same also for the Jupiter.

enter image description here

(this image shows a Sun-Earth solar sail, but the same could be done also for the Jupiter)

The sails should be in the L2 Lagrange point of the Sun-Jupiter system, which is unstable, but maybe in the case of such a big size, a stable configuration can be found.

enter image description here

(this image shows a Sun-Earth solar sail, but the same could be done also for the Jupiter)

Although the sail should be in the Sun-Jupiter system, it could be focused to any of the Jupiter-Moons.

Although it should be very big, it shouldn't be very thick. A micron thick aluminium is already enough to reflect sunlight. Thus, its mass shouldn't be very big, what makes the idea the most realistic one, although it is very far from Clarke's original idea.

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  • $\begingroup$ On #1 if you don't mind the extremely long timeline and energy expenditure, you could pull all the Hydrogen from Uranus and Neptune to Jupiter and also divert a distinct portion of the solar wind to Jupiter eventually getting to the 70 Jupiter masses for ignition. Of course you'd likely have to watch for the effects to other planets, asteroids, and Jupiters moons would likely need to be moved further out. On #3 you could also put the fusion reactors, either type, in direct orbit around Jupiter's moons. $\endgroup$ – Brooks Nelson Aug 11 '17 at 12:25
  • $\begingroup$ @BrooksNelson I don't know how long the Sun radiates away 70 Jupiter-mass Hidrogen, it would be likely a very long time, maybe in the order of billion years. It is around 7% of the total mass of the Sun. $\endgroup$ – Gray Sheep Aug 11 '17 at 13:12
  • $\begingroup$ Agreed, hence the 'extremely long timeline' I mentioned, though if we do starlifting to extend the life of the Sun the solar wind output would increase significantly. $\endgroup$ – Brooks Nelson Aug 11 '17 at 13:55

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