6 ms·

This is expected to be the ultimate fate of the gas giants (Jupiter, Saturn, Uranus, and Neptune) after the Sun leaves the main sequence in about 5 billion year

This is expected to be the ultimate fate of the gas giants (Jupiter, Saturn, Uranus, and Neptune) after the Sun leaves the main sequence in about 5 billion years. Within 30 billion years of the Sun becoming a red giant, Jupiter and Saturn are predicted to fall into a 5:2 orbital resonance that destabilizes the system, eventually causing all but 1 planet to be ejected within 30 billion years. The remaining planet is expected to be ejected within another 50 billion or so years.[0] So, within about 100 billion years, all that's going to be left of our solar system is a white dwarf (which will likely survive for trillions of years[1]), and 4 rogue planets, each drifting alone in space. Somehow, I think this little story is more interesting than the posted article, perhaps because it literally hits home. --- [0]: https://arxiv.org/pdf/2009.07296.pdf https://arxiv.org/pdf/2009.07296.pdf [1]: https://en.wikipedia.org/wiki/White_dwarf#Fate https://en.wikipedia.org/wiki/White_dwarf#Fate

jcims 5y ago
Understanding there's orders of magnitude of possible scale, what's the likelihood that one of these passing through the solar system would destabilize it enough to affect Earth? What happens if it hits the sun?
- vimacs2 5y ago
  Very low but a more common and likely possibility is that it could disturb the oort cloud and cause comets to fall in system. Guess that could classify as what you are referring to depending on your definition of solar system. A passing star is more likely to do this though and we believe that they indeed have caused disturbances in our oort cloud in the past. They might be potentially less numerous than rogue planets as our universe ages but they have a far larger potential hill sphere than even a very large planet so interactions with neighboring stars' hill spheres are more likely and frequent.
  - adolph 5y ago
    I've normally seen "oort" capitalized, so here is some background if others have the same question as me. The Oort cloud (/ɔːrt, ʊərt/),[1] sometimes called the Öpik–Oort cloud,[2] first described in 1950 by Dutch astronomer Jan Oort,[3] is a theoretical[4] concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 au (0.03 to 3.2 light-years).[note 1][5] It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space.[5][6] The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud. https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud
    - alistairSH 5y ago
      It was not very long ago that I realized the outer bounds of our Oort cloud are actually closer to Alpha Centauri (4.25 light years away) than the sun. The scale of the universe never ceases to elicit feelings of existential dread.
      - actually_a_dog 5y ago
        The outer edges of the cloud seem to be at ~100K AU [0], while the α Centauri system is ~268K AU from us [1]. NASA also gives the same number [2] for the distance to the edge of the cloud. So, it looks like the Cloud extends almost halfway to α Centauri, but not that it's "closer to α Centauri than us"). As for the scale of the Universe: https://htwins.net/scale2/ https://htwins.net/scale2/ --- [0]: https://en.wikipedia.org/wiki/Oort_cloud#/media/File:PIA17046_-_Voyager_1_Goes_Interstellar.jpg https://en.wikipedia.org/wiki/Oort_cloud#/media/File:PIA1704... [1]: https://imagine.gsfc.nasa.gov/features/cosmic/nearest_star_info.html https://imagine.gsfc.nasa.gov/features/cosmic/nearest_star_i... [2]: https://solarsystem.nasa.gov/solar-system/oort-cloud/overview/ https://solarsystem.nasa.gov/solar-system/oort-cloud/overvie...
        alistairSH 5y ago
        Huh, the first paragraph of that same wikipedia says the cloud extends to 2000 AU. Either way, whenever I try to think about these things, I feel mild anxiety. Why am I here? What's the point of all this? I'M SO TINY! Aaaahhhhhhhhh! I probably need to lay off the sci-fi novels for a while.
  - actually_a_dog 5y ago
    This sounds reasonable to me, assuming Mercury didn't either fall into the Sun or hit Venus. However, from the perspective of Earth, we might not notice this much, due to the effect of Jupiter (usually) either flinging comets away from us, or actually absorbing the impact of the comets.
- actually_a_dog 5y ago
  Ejection of the gas giants doesn't even take place until after the Sun has gone into its red giant phase. The Sun will swell so much that it engulfs the inner planets (Mercury, Venus, Earth, Mars), so, Earth won't even be around to become destabilized. Interestingly, the paper I linked talks about Mercury having a 1% chance of becoming unstable before the Sun enters its red giant phase: > The mechanism forthe onset of Mercury’s instability is well understood: by virtue of locking into a linear secular resonance with theg5mode of the solar system’s secular solution, Mercury’s eccentricity can attain near-unity values, resulting in a collision with the Sun, or even Venus. Intriguingly, General Relativistic effects factor into this estimate, with ancillary apsidal precession providing a stabilizing influence on Mercury’s orbit. If Mercury collides with the Sun, not much interesting will happen. Mercury doesn't have enough mass to disrupt the center of gravity of the Solar System when it falls into the Sun, so, all that will happen is that the planet will get vaporized, and the Sun will become infinitesimally more enriched in metals. If you were around to witness the event, it might be visually spectacular, but not particularly significant with respect to the fate of the system itself. They go on to say: > Within the context of this narrative, however, the remaining planets appear unaffected and are currently expected to remain stable for a lower limit of 10^18 years, when diffusion arising from the overlapping mean motion resonance of Jupiter and Saturn are expected to decouple Uranus. This analysis, however, is reflective of older studies, which don't take into account certain factors that this paper does.
  - kjs3 5y ago
    If Mercury collides with the Sun, not much interesting will happen. Yeah...but if it hits Venus......
ketanmaheshwari 5y ago
Would time even make any sense given that we use the very system to measure time.
- klodolph 5y ago
  We stopped using the solar system to measure time a while ago, and now use atomic clocks. Civil time is periodically adjusted to match the rotation of the Earth, but the amount of adjustment necessary is measured using atomic clocks, and atomic clocks are still the basis of civil time.
- actually_a_dog 5y ago
  Yes: > The second is defined as being equal to the time duration of 9,19,26,31,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental unperturbed ground-state of the caesium-133 atom. https://en.wikipedia.org/wiki/Second https://en.wikipedia.org/wiki/Second Unless the laws of physics aren't constant over very long time periods for some reason, we could (if we were around to do it) measure time 10^18 years from now just the same as we do today.
  - lizknope 5y ago
    In Oklo, Gabon there was a natural nuclear fission reactor about 1.7 billion years ago. The concentration of uranium and groundwater was just right that nuclear fission occurred naturally. We can measure the elements left behind and we have determined that the fine structure constant was the same then as it is now. If the laws of physics have remained constant for that long then most scientists think they will remain constant in the future. https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor#Relation_to_the_atomic_fine-structure_constant https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
    - actually_a_dog 5y ago
      Oh, sure, I wasn't saying the laws of physics were likely to change, simply that if they did, the SI definition of time might not be well posed. That said, although I agree the laws of physics are likely to remain constant, 1.7 billion years is only just about 12% of the age of the Universe. And, that time period only reflects the most recent 1.7 billion years. So, there's still some theoretical wiggle room there for the fine structure constant to vary over time. After all, heat death is not expected to occur for much more 100 trillion years (if that is our ultimate fate)! [0] Edit: Come to think of it, if the laws of physics aren't constant, how would it be possible to pose a coherent definition of a unit of time at all? --- [0]: https://en.wikipedia.org/wiki/Future_of_an_expanding_universe#Degenerate_Era https://en.wikipedia.org/wiki/Future_of_an_expanding_univers...
Florin_Andrei 5y ago
Okay, so as long as you have 3 or more bodies, I understand ejection. Energy gets transferred semi-randomly such that eventually one body gains too much energy and shoots out. But when N=2, what is the ejection mechanism? That's an elliptical orbit that should be spinning round and round forever (sans the losses via gravitational waves).
- actually_a_dog 5y ago
  You mean how does the last planet get ejected? Well, that's an interesting question, actually. Because of the inherent stability of the 2 body system, the last planet gets ejected some ~50 billion years after the others. The authors' simulation takes into account the fact that a star comes close enough to the Solar System to have some tangible effect every 23M years or so. It's the cumulative effect of these stellar flybys that eventually nudges the last planet out of the system.
  - Florin_Andrei 5y ago
    Ok, external perturbation, got it. Yeah, that makes sense. Otherwise it would just very slowly spiral in, due to losses from general relativity.
    - actually_a_dog 5y ago
      Yep, and loss of angular momentum due to it being carried away by gravity waves would probably take many trillions of years, I would guess.
  - ByThyGrace 5y ago
    > the fact that a star comes close enough to the Solar System to have some tangible effect every 23M years or so Do you have a good source that expands on this? That sounds so interesting.
aquova 5y ago
Assuming the gas giants remain roughly the same as they are now, what would happen to them as they left the solar system and the heat of the sun? Would the gases condense down turning them from gas giants into rocky planets?
- Tuna-Fish 5y ago
  Eventually, but it would take much, much longer than you'd think. Jupiter, Saturn and Neptune all radiate ~2x the heat they receive from the Sun. Most of their heat is primordial, residue from the gravitational potential energy of all their component parts falling together. A gas giant flung away from it's host star will likely remain more or less as it is much longer than the star is.
  - actually_a_dog 5y ago
    Just to add on to this, NASA estimates that the internal core temperature of Jupiter could be as hot as 24,000°K [0]. For reference, the Sun's photosphere has a temperature of about 6000°K [1]. --- [0]: https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-jupiter-58.html https://www.nasa.gov/audience/forstudents/5-8/features/nasa-... [1]: https://www.scientificamerican.com/article/i-read-that-the-suns-surf/ https://www.scientificamerican.com/article/i-read-that-the-s...
    - hollerith 5y ago
      For reference the temperature at the center of the sun is about 15 million °K
    - perl4ever 5y ago
      >the Sun's photosphere has a temperature of about 6000° There was a paper that proposed that Earth's surface was about this hot for a while after the collision that formed the Moon. Even though the heat wasn't coming from nuclear fusion, for a while it was just as hot as a star, so the Moon, which was smaller and cooled faster overall, was remelted in places by "Earthshine" - therefore the discrepancy between the maria on the near side and the far side.
perl4ever 5y ago
>Within 30 billion years of the Sun becoming a red giant The Sun isn't expected to remain a red giant for 30 billion years, is it? More like a tenth of that, I thought.
temporallobe 5y ago
Please forgive me, I am not a cosmologist, merely a humble software engineer - but your timespans of 30+ billion and into “trillions” of years seem awfully askew. The age if the entire universe is estimated at “only” 13.77 billion years old, so how is this possible? Are we simply in an extremely young universe?
- jhgb 5y ago
  > Are we simply in an extremely young universe? Well, in the set of positive reals, any number you randomly pick will be very small compared to the vast majority of all the numbers in the set.
  - morpheos137 5y ago
    Yeah because the age of the universe can't be negative.
    - pieceoffeces 5y ago
      Who let you out of your cage? I thought lowlifes with enlarged brains weren't allowed out of their cells. dang, why did you give this human a pass?
      - morpheos137 5y ago
        Is this the reddit culture infecting hn the other poster was complaining about? Stop being a little brother. cf 1984.
- tbabb 5y ago
  Yes, by our current cosmological models, we are in a very young universe. We don't really know, but it may be the case that the universe is only conducive to life during this phase of its existence.
- XorNot 5y ago
  See also: it's quite likely that no red dwarf anywhere in existence has run out of fuel, yet - some are estimated to last as long as 10 trillion years.

jcims 5y ago

Understanding there's orders of magnitude of possible scale, what's the likelihood that one of these passing through the solar system would destabilize it enough to affect Earth? What happens if it hits the sun?

vimacs2 5y ago
Very low but a more common and likely possibility is that it could disturb the oort cloud and cause comets to fall in system. Guess that could classify as what you are referring to depending on your definition of solar system. A passing star is more likely to do this though and we believe that they indeed have caused disturbances in our oort cloud in the past. They might be potentially less numerous than rogue planets as our universe ages but they have a far larger potential hill sphere than even a very large planet so interactions with neighboring stars' hill spheres are more likely and frequent.
- adolph 5y ago
  I've normally seen "oort" capitalized, so here is some background if others have the same question as me. The Oort cloud (/ɔːrt, ʊərt/),[1] sometimes called the Öpik–Oort cloud,[2] first described in 1950 by Dutch astronomer Jan Oort,[3] is a theoretical[4] concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 au (0.03 to 3.2 light-years).[note 1][5] It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space.[5][6] The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud. https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud
  - alistairSH 5y ago
    It was not very long ago that I realized the outer bounds of our Oort cloud are actually closer to Alpha Centauri (4.25 light years away) than the sun. The scale of the universe never ceases to elicit feelings of existential dread.
    - actually_a_dog 5y ago
      The outer edges of the cloud seem to be at ~100K AU [0], while the α Centauri system is ~268K AU from us [1]. NASA also gives the same number [2] for the distance to the edge of the cloud. So, it looks like the Cloud extends almost halfway to α Centauri, but not that it's "closer to α Centauri than us"). As for the scale of the Universe: https://htwins.net/scale2/ https://htwins.net/scale2/ --- [0]: https://en.wikipedia.org/wiki/Oort_cloud#/media/File:PIA17046_-_Voyager_1_Goes_Interstellar.jpg https://en.wikipedia.org/wiki/Oort_cloud#/media/File:PIA1704... [1]: https://imagine.gsfc.nasa.gov/features/cosmic/nearest_star_info.html https://imagine.gsfc.nasa.gov/features/cosmic/nearest_star_i... [2]: https://solarsystem.nasa.gov/solar-system/oort-cloud/overview/ https://solarsystem.nasa.gov/solar-system/oort-cloud/overvie...
      - alistairSH 5y ago
        Huh, the first paragraph of that same wikipedia says the cloud extends to 2000 AU. Either way, whenever I try to think about these things, I feel mild anxiety. Why am I here? What's the point of all this? I'M SO TINY! Aaaahhhhhhhhh! I probably need to lay off the sci-fi novels for a while.
- actually_a_dog 5y ago
  This sounds reasonable to me, assuming Mercury didn't either fall into the Sun or hit Venus. However, from the perspective of Earth, we might not notice this much, due to the effect of Jupiter (usually) either flinging comets away from us, or actually absorbing the impact of the comets.
actually_a_dog 5y ago
Ejection of the gas giants doesn't even take place until after the Sun has gone into its red giant phase. The Sun will swell so much that it engulfs the inner planets (Mercury, Venus, Earth, Mars), so, Earth won't even be around to become destabilized. Interestingly, the paper I linked talks about Mercury having a 1% chance of becoming unstable before the Sun enters its red giant phase: > The mechanism forthe onset of Mercury’s instability is well understood: by virtue of locking into a linear secular resonance with theg5mode of the solar system’s secular solution, Mercury’s eccentricity can attain near-unity values, resulting in a collision with the Sun, or even Venus. Intriguingly, General Relativistic effects factor into this estimate, with ancillary apsidal precession providing a stabilizing influence on Mercury’s orbit. If Mercury collides with the Sun, not much interesting will happen. Mercury doesn't have enough mass to disrupt the center of gravity of the Solar System when it falls into the Sun, so, all that will happen is that the planet will get vaporized, and the Sun will become infinitesimally more enriched in metals. If you were around to witness the event, it might be visually spectacular, but not particularly significant with respect to the fate of the system itself. They go on to say: > Within the context of this narrative, however, the remaining planets appear unaffected and are currently expected to remain stable for a lower limit of 10^18 years, when diffusion arising from the overlapping mean motion resonance of Jupiter and Saturn are expected to decouple Uranus. This analysis, however, is reflective of older studies, which don't take into account certain factors that this paper does.
- kjs3 5y ago
  If Mercury collides with the Sun, not much interesting will happen. Yeah...but if it hits Venus......

ketanmaheshwari 5y ago

Would time even make any sense given that we use the very system to measure time.

klodolph 5y ago
We stopped using the solar system to measure time a while ago, and now use atomic clocks. Civil time is periodically adjusted to match the rotation of the Earth, but the amount of adjustment necessary is measured using atomic clocks, and atomic clocks are still the basis of civil time.
actually_a_dog 5y ago
Yes: > The second is defined as being equal to the time duration of 9,19,26,31,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental unperturbed ground-state of the caesium-133 atom. https://en.wikipedia.org/wiki/Second https://en.wikipedia.org/wiki/Second Unless the laws of physics aren't constant over very long time periods for some reason, we could (if we were around to do it) measure time 10^18 years from now just the same as we do today.
- lizknope 5y ago
  In Oklo, Gabon there was a natural nuclear fission reactor about 1.7 billion years ago. The concentration of uranium and groundwater was just right that nuclear fission occurred naturally. We can measure the elements left behind and we have determined that the fine structure constant was the same then as it is now. If the laws of physics have remained constant for that long then most scientists think they will remain constant in the future. https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor#Relation_to_the_atomic_fine-structure_constant https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
  - actually_a_dog 5y ago
    Oh, sure, I wasn't saying the laws of physics were likely to change, simply that if they did, the SI definition of time might not be well posed. That said, although I agree the laws of physics are likely to remain constant, 1.7 billion years is only just about 12% of the age of the Universe. And, that time period only reflects the most recent 1.7 billion years. So, there's still some theoretical wiggle room there for the fine structure constant to vary over time. After all, heat death is not expected to occur for much more 100 trillion years (if that is our ultimate fate)! [0] Edit: Come to think of it, if the laws of physics aren't constant, how would it be possible to pose a coherent definition of a unit of time at all? --- [0]: https://en.wikipedia.org/wiki/Future_of_an_expanding_universe#Degenerate_Era https://en.wikipedia.org/wiki/Future_of_an_expanding_univers...

Florin_Andrei 5y ago

Okay, so as long as you have 3 or more bodies, I understand ejection. Energy gets transferred semi-randomly such that eventually one body gains too much energy and shoots out. But when N=2, what is the ejection mechanism? That's an elliptical orbit that should be spinning round and round forever (sans the losses via gravitational waves).

actually_a_dog 5y ago
You mean how does the last planet get ejected? Well, that's an interesting question, actually. Because of the inherent stability of the 2 body system, the last planet gets ejected some ~50 billion years after the others. The authors' simulation takes into account the fact that a star comes close enough to the Solar System to have some tangible effect every 23M years or so. It's the cumulative effect of these stellar flybys that eventually nudges the last planet out of the system.
- Florin_Andrei 5y ago
  Ok, external perturbation, got it. Yeah, that makes sense. Otherwise it would just very slowly spiral in, due to losses from general relativity.
  - actually_a_dog 5y ago
    Yep, and loss of angular momentum due to it being carried away by gravity waves would probably take many trillions of years, I would guess.
- ByThyGrace 5y ago
  > the fact that a star comes close enough to the Solar System to have some tangible effect every 23M years or so Do you have a good source that expands on this? That sounds so interesting.

aquova 5y ago

Assuming the gas giants remain roughly the same as they are now, what would happen to them as they left the solar system and the heat of the sun? Would the gases condense down turning them from gas giants into rocky planets?

Tuna-Fish 5y ago
Eventually, but it would take much, much longer than you'd think. Jupiter, Saturn and Neptune all radiate ~2x the heat they receive from the Sun. Most of their heat is primordial, residue from the gravitational potential energy of all their component parts falling together. A gas giant flung away from it's host star will likely remain more or less as it is much longer than the star is.
- actually_a_dog 5y ago
  Just to add on to this, NASA estimates that the internal core temperature of Jupiter could be as hot as 24,000°K [0]. For reference, the Sun's photosphere has a temperature of about 6000°K [1]. --- [0]: https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-jupiter-58.html https://www.nasa.gov/audience/forstudents/5-8/features/nasa-... [1]: https://www.scientificamerican.com/article/i-read-that-the-suns-surf/ https://www.scientificamerican.com/article/i-read-that-the-s...
  - hollerith 5y ago
    For reference the temperature at the center of the sun is about 15 million °K
  - perl4ever 5y ago
    >the Sun's photosphere has a temperature of about 6000° There was a paper that proposed that Earth's surface was about this hot for a while after the collision that formed the Moon. Even though the heat wasn't coming from nuclear fusion, for a while it was just as hot as a star, so the Moon, which was smaller and cooled faster overall, was remelted in places by "Earthshine" - therefore the discrepancy between the maria on the near side and the far side.

perl4ever 5y ago

>Within 30 billion years of the Sun becoming a red giant The Sun isn't expected to remain a red giant for 30 billion years, is it? More like a tenth of that, I thought.

temporallobe 5y ago

Please forgive me, I am not a cosmologist, merely a humble software engineer - but your timespans of 30+ billion and into “trillions” of years seem awfully askew. The age if the entire universe is estimated at “only” 13.77 billion years old, so how is this possible? Are we simply in an extremely young universe?

jhgb 5y ago
> Are we simply in an extremely young universe? Well, in the set of positive reals, any number you randomly pick will be very small compared to the vast majority of all the numbers in the set.
- morpheos137 5y ago
  Yeah because the age of the universe can't be negative.
  - pieceoffeces 5y ago
    Who let you out of your cage? I thought lowlifes with enlarged brains weren't allowed out of their cells. dang, why did you give this human a pass?
    - morpheos137 5y ago
      Is this the reddit culture infecting hn the other poster was complaining about? Stop being a little brother. cf 1984.
tbabb 5y ago
Yes, by our current cosmological models, we are in a very young universe. We don't really know, but it may be the case that the universe is only conducive to life during this phase of its existence.
XorNot 5y ago
See also: it's quite likely that no red dwarf anywhere in existence has run out of fuel, yet - some are estimated to last as long as 10 trillion years.