Q: How close is Jupiter to being a star? What would happen to us if it were?

The original question was: I have heard Jupiter referred to as a failed star.  That if the cosmic chaos of the early solar system had worked out a little different, and Jupiter had gotten a bit more mass, it might have been able to light the fusion engine and become a star.

Two questions.

How close was Jupiter to becoming a star?

If something really big slammed into Jupiter today, could it trigger nuclear fusion?

Ok and a third question.  If Jupiter did in fact get slammed with something big enough to trigger nuclear fusion, and it became a star, how long would it take to substantially alter the ability for earth to sustain life as we know it?


Physicist: That is a really cool question!

I heard the same thing a while ago, but Jupiter is a long way from being a star.  That estimate was based on some old nuclear physics (like 1980′s old).  By being awesome, and building neutrino detectors and big computers, we’ve managed to refine our understanding of stellar fusion a lot in the last few decades.

Although the material involved (how much hydrogen, how much helium, etc.) can change the details, most physicists (who work on this stuff) estimate that you’d need at least 75-85 Jupiter masses to get fusion started.  By the time a planet is that large the lines between planet, brown dwarf (failed star), and star gets a little fuzzy.

So, for Jupiter to become a star you’d need to slam so much additional mass into it, that it would be more like Jupiter slamming into the additional mass.

If you were to replace Jupiter with the smallest possible star it would have very little impact here on Earth.

There’s some debate over which star is the smallest star (seen so far).  OGLE-TR-122b, Gliese 623b, and AB Doradus C are among the top contenders (why is every other culture better at naming stars?), and all weigh in around 100 Jupiters.  They are estimated to be no more than 1/300th, 1/60,000th, and 1/1,000th as bright as the Sun respectively.  So, lets say that Jupiter suddenly became “OGLupiter” (replaced by OGLE-TR-122b, the brightest of the bunch, and then given the worst possible name).  It would be a hundred times more massive, 20% bigger, a hell of a lot denser, and about 0.3% as bright as the Sun.

At it’s closest Jupiter is still about 4 times farther away from us than the Sun, so OGLupiter would increase the total energy we receive by no more than about 1 part in 5 thousand (about 0.02%).  This, by the way, is much smaller than the 6.5% yearly variation we get because of the eccentricity of Earth’s orbit (moving closer and farther away from the Sun over the course of a year).  There would be effectively zero impact on Earth’s life.

There are examples of creatures on Earth that use the moon for navigation, so maybe things would eventually evolve to use OGLupiter for navigation or timing or something.  But it’s very unlikely that anything would die.

OGLupiter would be around 80 times brighter than a full moon at its brightest, so for a good chunk of every year, you’d be able to read clearly at night.  It would be very distinctively red (being substantially colder than the Sun), and it would be clearly visible even during the day.

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94 Responses to Q: How close is Jupiter to being a star? What would happen to us if it were?

  1. Javier C says:

    What if all of the outer planets were collide with jupiter. Would that be enough to start the fusion process or is it that far away from becoming a star?

  2. The Physicist The Physicist says:

    It’s that far away. Even with the other planets Jupiter’s mass wouldn’t even double.

  3. CJ says:

    would OGLupiter have an effect on Mars and Saturn? if so what type of changes would we possibly see?

  4. Susan says:

    I read that Gliese 710, an Orange Dwarf star, is on course to arrive at our Solar System in 1.5 million years, at its closest approach. Since Orange Dwarf stars are the most coveted of all stars for sustaining life in habitable zones, will it provide the mass needed to turn Neptune, Jupiter, etc. into Stars? Could their satellite moons become unlocked and begin rotating around the new star, forming mini-Solar Systems in our Galaxy? For example, Saturn and Uranus would become mini-Solar Systems, possibly breaking away from our Solar System? Vadim Bobylev, 2010.

    Thank you.

  5. The Physicist The Physicist says:

    It’s expected to pass well outside the solar system, but even if it passed well inside of our solar system it wouldn’t add mass to anything. Instead, it would just muck things up and throw things around.

  6. Silent says:

    Wouldn’t OGLupiter’s increased gravitational field mess with our orbit, eather pulling us farther away from the sun thus shifting our climate or causing orbital resonance between the sun, us and OGLupiter? Also what about OGLupiter’s magnetic fields, what effects would those have?

    Thanks

  7. The Physicist The Physicist says:

    That’s something I forgot to consider in the post, but that got brought up pretty early in the comment thread. Jupiter being 10 times more massive would put the solar system’s center of mass neatly between the Sun and the Earth’s orbit, which would make our present orbit very unstable.
    It’s pretty unlikely that OGLupiter’s magnetic field would change much here on Earth. Both the Sun and Jupiter already have mammoth magnetic fields, and they don’t affect us too much.

  8. Am doing a study on Jupiter and some of my finding give the impression of what is on course to our solar system in respect to history and future of the celestial bodies within our solar system. Jupiter is not dwarfed or retarded as some opinions suggest, but what is actually seen is an advanced level of cooling to which our own sun is heading to. Now this may sound absurd but one needs to do a lot of research on many things not only in cosmology or astronomy. Nature exists in family pertains. Decerning this will certainly take quiet some sacrifice.

  9. Mike Rosoft says:

    I remember seeing an interesting scenario in a Czech TV popular astronomy series, “Okna vesmíru dokořán” (Windows of the Universe Wide Open). When the Sun becomes a red giant, it would expand so much that it would destroy the inner planets of the solar system, including the Earth and Mars, but Jupiter might actually collect enough matter from the expanding Sun by moving through the Sun’s atmosphere that it would become a red dwarf star.

    Do you think this could be possible (perhaps if Jupiter were closer to the Sun, where Mars or the Earth is now)?

  10. The Physicist The Physicist says:

    Probably not. Jupiter is a long way from stardom.

  11. William says:

    I would like to start out by saying, outstanding work on understand they parts to all of this. It is good to see someone else with a similar understand as me. But, I would also like to say that even though Jupiter is no where near nuclear fusion, it is, (in my mind) around the possibility of it being a brown dwarf star. Tell me what you think of this and maybe sometime we could discuss this further, I would very much enjoy a conversation with someone else with similar knowledge.

  12. Tim says:

    What is the potential for our solar system to encounter pockets of hydrogen that Jupiter could gravitationally capture as our solar system moves through the milky way?

  13. Yves says:

    So Jupiter needs to be much more weighty to give it a chance to become a star – let’s keep Jupiter as it is:
    what about alternative scenarii that would make Jupiter a burning planet? I.e. igniting in some way the planet so that it emits a great deal of light/heat? Does the current “air” composition of Jupiter allows that kind of “burning digression”?

  14. The Physicist The Physicist says:

    Nope! The only place in the known universe that can support an open flame is the atmosphere here on Earth.

  15. Beau says:

    What would happen if we were to launch a nuke into jupiter (granted we have the technology for it). Would it be able to ignite anything?

  16. The Physicist The Physicist says:

    Nope!
    We can definitely nuke Jupiter (this is not a new idea!), but we might not even be able to detect the “pop”. Jupiter is crazy big.

  17. Rory says:

    Hello! Unrelated but you seem like a cleaver person and no one else seems to be able to shed light on my question!! I was wondering if it would be in theory possible to fuse two dissimilar atoms together in a nuclear reaction?? Could this be the origin of dark matter? Don’t laugh!

  18. The Physicist The Physicist says:

    Unmatched elements can fuse, it’s just that we usually only hear about hydrogen (which is the most commonly fused, and the most common element period). While the math is more difficult, there’s nothing particularly special about “mixed fusion” (seems like a good name for it). This is very unlikely to be a good place to look for dark matter.

  19. PT says:

    Earlier you mentioned that OGLupiter’s increased gravitational field could have the effect of making our present orbit very unstable. How severe would this destabilization be? What kind of effects could it have on the Earth?

  20. Starkhead says:

    “Physicist: That is a really cool question!”
    Sounds like Alexei V. Filippenko, lol.

    BTW thanks for the details !

  21. Jared says:

    What if we were able to somehow artificially increase Jupiter’s gravity without increasing it’s size. Would it then change into a star?
    (possibly a stupid question)

  22. The Physicist The Physicist says:

    @Jared
    That would probably do the trick. Unfortunately, outside of lots of matter, there’s no good way to increase gravity.

  23. Shane says:

    But if OGLupiter were big enough to become a star wouldn’t the gravity of it pull other planets out of alignment? Also I don’t believe Jupiter could become a star even if it was big enough due to the fact that according to hypothesis it contains a rocky core that may contain iron which by all accounts is a star killer.

  24. Kody says:

    If the additional mass would be greater than that of jupiter, what about additional ENERGY instead? would the equivalent energy be posible to create here on earth and couold we use it on jupiter to convert it into a posible star?

  25. Reaz H says:

    Very interesting and easy to read analysis. Well done. However, it seems the effect of increased light on animal life is neglected. While the additional amount of energy transmitted from Jupiter is minimal, the comment about Jupiter being 80 times brighter than the moon (at night) is slightly worrisome. I wonder how it would affect photosynthesis and sleep cycle in animals.

  26. Parvin Desai says:

    I have a question ,, Could stars fuse without gravity ?

  27. Khan says:

    If Jupiter did become a star would it stop its revolution around the sun and affect the revolution of Earth and other planets revolving around the sun?

  28. Khan says:

    (A Science-Fiction Question for current technology) If we were able to say strap an antimatter engine to the core of Jupiter and accelerate the rotation of the planet perhaps exponentially could that create gravity and pull the celestial body together and into a star or something of the sort?

  29. Shane says:

    Why would jupiter stop orbiting? All celestial bodies orbit other celestial bodies. Jupiter becoming a star wouldn’t stop that. I would be worried that it would disrupt the orbits of everything else in our solar system but the sun and OGlupiter would most likely become a binary star system. Which are pretty common in the universe

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  31. How much longer could we make our sun burn using Jupiter as fuel?

  32. The Physicist The Physicist says:

    Not a lot longer. The Sun is 99.85% of the mass of the solar system, so Jupiter is just a drop in the bucket.

  33. Kevin says:

    I recall hearing somewhere several years ago that Jupiter’s gravity or orbital resonance might be responsible for causing or limiting Earth’s axial tilt. Like it has helped create seasons. I know it seems unlikely, but we do have 4 billion years to work with, and turtles are pretty unlikely too. It might have been an article in Griffith Observer. I’d like to believe it, I hope it wasn’t by John Gribben.

  34. Evan says:

    Fantastic post and great responses!

    Are there any scenarios with solar systems where this type of dynamic plays out? Eg star creation within an existing solar system? I’m not sure of the scenario but maybe a collision with a large just cloud? And assuming this occurs would it result in the eventual collapse of planetary orbits?

  35. margaret prentice says:

    Is a nuclear plant melt down equivelant to the birth of a new star. And are the four new molecules that outcrop through the melt down procedure possible what is foreseen and described as wormwood?

  36. cire says:

    why nt pull the other jovian planets to collid with jupiter in orda to increase jupiters mass?

  37. nonburiguy says:

    Can human just trigger a fusion on Jupiter without the needs of massive mass,
    Since it doesn’t need that much of mass in fusion power plant or bomb.
    Maybe with a next 1000 years technology.

  38. Shane says:

    Even if you could trigger a fusion reaction without adding the mass I don’t think there’s enough fuel to keep it burning for very long

  39. Ajay says:

    When the sun dies after 4.5billion years, it ejects most of its mass throughout the solar system. Will that mass be sufficient to feed Jupiter, to become a star, or in other words, will Jupiter becomes the successor of sun, with all its moons as planets.

  40. The Physicist The Physicist says:

    @Ajay
    Pretty unlikely, although that would be pretty cool.

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  43. Stephen says:

    This is probably asilly question, and might have already been asked, but everyone is talking about “Jupiter ALMOST being a star”, but what if it already WAS a star? is that a possibility or am I WAY out of my head?

  44. SteveA says:

    Okay, this is as far as I know about 15 million years plus into the future, but wouldn’t launching enough hydrogen antimatter into Jupiter cause fusion?

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