In 2010: The Year We Make Contact, the climax of the film is quite bizarre. Jupiter's mass is replaced by billions of black monoliths, eventually collapsing in on itself and becoming a star.

Europa becomes a vibrant planet full of life, although humans are forbidden to go there; the other new planets (the former moons of Jupiter) are given to humanity, for us to use in peace and goodwill.

However, it seems like a planet suddenly turning into a second star within our own solar system would have catastrophic consequences for the earth and everyone on it, and would probably cause all kinds of other problems for the rest of the solar system as well.

Why didn't terrible things happen when Jupiter became a star?

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    I didn't see the film, only read the book recently. I thought it was turned into a starlet ("Lucifer") with a mass equal to Jupiter. So from a gravity/orbit perspective, it's business as usual.
    – Oliphaunt
    Commented Jun 24, 2015 at 20:46
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    @calccrypto : Our solar system is a 10-body problem (I'm counting Pluto here). Replacing one of the masses or dramatically altering one of the masses will have effects for the short- and long-term dynamics of the solar system.
    – Praxis
    Commented Jun 24, 2015 at 20:47
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    I have never heard of a "starlet" (aside from the "Hollywood Starlet" variety), and it appeared to me that the mass of Jupiter was drastically increased. The monoliths replaced the substance of Jupiter, making it far more massive, and causing it to collapse on itself, which is how it became a star.
    – Wad Cheber
    Commented Jun 24, 2015 at 20:49
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    A species that can Kickstart evolution and astroform planets into stars, who essentially created humanity and wants to keep us around, will be smart enough to plan their technology to not willy nilly throw entire systems out of alignment. That said, Jupiter already exerts a pull on us and on the sun. And any changes to its mass would take astronomical time spans to affect other planets in the system.
    – user16696
    Commented Jun 24, 2015 at 21:45
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    @Wad I feel like you have the assumption that things orbit the sun because it's a star. In reality everything in the solar system orbits the center of mass of the solar system, including the sun. Include that with the other answer that the mass didn't change means the orbits will be unaffected. Commented Jun 25, 2015 at 14:22

4 Answers 4


This is explained in the novel 2010: Odyssey Two. Jupiter's mass hasn't changed.

It follows that there's no need to reconfigure the solar system to accommodate it:

Do you have any idea what happened?’
‘Only that Jupiter’s turned into a sun.’
‘I always thought it was much too small for that. Didn’t someone once call Jupiter “the sun that failed”?’
‘That’s true,’ said Vasili, ‘Jupiter is too small for fusion to start - unaided.’
‘You mean, we’ve just seen an example of astronomical engineering?’
‘Undoubtedly. Now we know what Zagadka was up to.’
‘How did it do the trick? If you were given the contract, Vasili, how would you ignite Jupiter?’
Vasili thought for a minute, then shrugged wryly. ‘I’m only a theoretical astronomer - I don’t have much experience in this line of business. But let’s see… Well, if I’m not allowed to add about ten Jupiter masses, or change the gravitational constant, I suppose I’ll have to make the planet denser - hmm, that’s an idea…’
His voice trailed off into silence; everyone waited patiently, eyes flickering from time to time to the viewing screens.
The star that had been Jupiter seemed to have settled down after its explosive birth; it was now a dazzling point of light, almost equal to the real Sun in apparent brilliance. ‘I’m just thinking out loud - but it might be done this way. Jupiter is - was - mostly hydrogen. If a large percentage could be converted into much denser material - who knows, even neutron matter? - that would drop down to the core. Maybe that’s what the billions of Zagadkas were doing with all the gas they were sucking in. Nucleosynthesis - building up higher elements from pure hydrogen. That would be a trick worth knowing! No more shortage of any metal - gold as cheap as aluminium!’

There are some consequences on Earth though, mostly relating to the addition of an extra small sun to the sky:

the end of night had vastly extended the scope of human activity, especially in the less-developed countries. Everywhere, the need for artificial lighting had been substantially reduced, with resulting huge savings in electrical power.


Many nocturnal creatures had been seriously affected, while others had managed to adapt. The Pacific grunion, whose celebrated mating pattern was locked to high tides and moonless nights, was in grave trouble, and seemed to be heading for rapid extinction.

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    @WadCheber - You can't really get any better that the author writing "it didn't change, so ner".
    – Valorum
    Commented Jun 24, 2015 at 21:15
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    Out of universe it's not feasible. Just making the same amount of mass "more dense" won't suddenly give it enough gravity to kick-start fusion. OTOH, a star the size of Jupiter in Jupiter's place would dump a tiny, tiny fraction of a percent of extra energy on us -- less than the seasonal variation we already get from the sun, so we'd barely notice. At best, it would be a few dozen times brighter than the moon if the orbits lined up right.
    – KutuluMike
    Commented Jun 25, 2015 at 0:33
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    @Michael Edenfield - Are you sure making it more dense wouldn't kick-start fusion? Attempts to create a fusion reactor on Earth rely on confining nuclei to a very high density and temperature, not changing gravity. And if you chose a small radius from the center of the Sun, of just the right size so that the mass within that radius was equal to the mass of Jupiter, then it would be much denser than Jupiter due to the pressure from above, but by the shell theorem it wouldn't feel gravity from the matter above.
    – Hypnosifl
    Commented Jun 25, 2015 at 2:48
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    (but maybe you meant that if the monoliths ever stopped exerting their influence on it, the gravity wouldn't be enough to hold it at that density, and it would just expand back out and fusion would stop--if so I agree the situation would be "unnatural" in that sense, the monoliths would have to continually be there creating a force field or whatever other magic they do to keep it compressed)
    – Hypnosifl
    Commented Jun 25, 2015 at 2:51
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    @Hypnosifl - The light from Lucifer only lasts a few thousand years, if I recall correctly.
    – Valorum
    Commented Jun 25, 2015 at 5:03

I meant catastrophic in the sense that the orbits would be thrown into chaos. Everything would want to orbit both the sun and the new star

No, they wouldn't.

Planets orbit a star because the star is much bigger, not because it is a star. Replace our sun with 2^30 kg of caramel pudding and absolutely nothing will change (other than getting colder). Jupiter is too far away from us (and too small) to provide significant heat; the only effect is extra illumination for half the year. The results are well explained in the book.

Igniting Jupiter was done by manipulating its density. Increasing its mass would have pulled the Jovian satellites into it, which would more-or-less defeat the purpose of the experiment.

In-universe, the responsible entity appears to be an omnipotent expert in astronomical engineering - we can assume that they have done the math correctly.

In-between-universe, the book goes into a lot more detail. The movie doesn't have an extra hour to devote to the hard science.

Out of universe, Arthur C. Clarke was one of the (if not the) leading authors of hard sci-fi. The whole thing has been thought through very carefully.

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    @WadCheber The answer is relevant, as it is addressing your question. The quoted comment (which clarifies your statment "However, it seems like a planet suddenly turning into a second star within our own solar system would have catastrophic consequences ..." does a good job of setting up the answer.
    – Trisped
    Commented Jun 25, 2015 at 0:05
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    The quoted comment did a better job of phrasing the question than the question itself. Read both, compare...
    – paul
    Commented Jun 25, 2015 at 3:26
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    “Replace our sun with 2^30 kg of caramel pudding and absolutely nothing will change (other than getting colder)” Excellent engineer statement :) Commented Jun 25, 2015 at 8:25
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    @PaulD.Waite I'm rather curious if the pudding would have enough density in the core to ignite. And if yes, would it stabilise as a crème brûlée instead of continuing down the fusion chain.
    – paul
    Commented Jun 25, 2015 at 10:17
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    @paul: there aren’t enough upvotes in the world for that comment. Commented Jun 25, 2015 at 10:21

The mass of Jupiter remained the same; the black monoliths increased its density until it began fusing hydrogen. Since its mass did not change, the orbits of our solar system would not be affected.

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    This doesn't make sense to me, volume would have to decrease for density to increase without also increasing mass.
    – onewho
    Commented Jun 24, 2015 at 20:57
  • Thanks. I'm not sure if that makes scientific sense, but it does explain the problem according to the internal logic of the story. +1
    – Wad Cheber
    Commented Jun 24, 2015 at 20:58
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    I agree with @onewho. The volume must be decreasing. Is Jupiter also contracting in on itself in the story?
    – Praxis
    Commented Jun 24, 2015 at 21:10
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    @Praxis - it does collapse in on itself.
    – Wad Cheber
    Commented Jun 24, 2015 at 21:23
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    reading richards post it does appear that the volume is decreasing. which would fit into onewho's idea.
    – Himarm
    Commented Jun 24, 2015 at 21:29

Scientifically in order for Jupiter to become the smallest type of standard star star (red dwarf) you would need 79 more jupiters to condense together. However a red dwarf doesn't emit the same kind of energy as our sun, it is far more radioactive.

Creating a star the size Jupiter is now that emits the same kind of light and heat as the sun does is impossible based on the laws of physics as we know them today

Now when Arthur C Clarke wrote 2010 the failed sun theory was an accepted theory. Given that Clarke always tried to base his stories on science I think he would write this whole section very differently today given we now know the above.

If jupiters mass was increased then the solar system would become a binary system with the center positioned somewhere between the 2 stars. This would change the orbit of every planet in the solar system (or destroy them all).

Basically with the scientific facts of the time Clarke kept the mass equal. If he wrote it today I imagine he would change the ending of that story.

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    " in order for Jupiter to become the smallest type of standard star" Note the word standard. In the novels, Jupiter was being manipulated by ridiculously advanced entities using incomprehensibly advanced technology, so comparing what they did with standard stellar evolution would be like comparing how tall an engineered structure could be versus how tall a tree can grow. Same physical laws in effect, very different results. Commented Mar 8, 2019 at 20:45

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