Earth ejected from solar system

[Xibalba]

Hi.

For a science-fiction-based fantasy story, the Earth has been ejected from the solar system by interacting with a roaming planet from outer space. Eventually, it ends orbiting the last star, which is a red dwarf, because of the entropy of the universe. So that's quite far in the future.

I've got some questions, though.

Will the Earth keep its atmosphere in outer space? Or what are the odds it does/doesn't?

Will the Earth keep its moon?

Will the Earth's magnetic field still be up, and will the convections happening in the Earth still be happening?

Thanks!

[danscope]

The Earth would simply get mighty cold. And since the nearest star is 4 light years away and likely to stay there, it doesn't look like Earth will be in the viscinity of a new home star any time soon. (It would take some extraordinary motion and influence to
eject Earth from it's orbit and direct it out of system ).

[Swift]

Most of the atmosophere would like freeze out onto the surface.

I suspect that a close enough pass from a roaming planet, close enough to eject the Earth, would also eject the Moon, and I suspect the Moon would go off in a different direction, but I'm not sure. I think such an event would be pretty chaotic.

The Earth would keep its magnetic field. I suspect that in intergalactic space it would loss a little more heat, and the core would freeze out a little faster, but until that time it would keep its field. Once the core froze, there would probably continue to be a residual magnetic field, though probably of much weaker strength.

[Noclevername]

Will the Earth's magnetic field still be up, and will the convections happening in the Earth still be happening?

If we're talking far enough in the future that one red dwarf is the only star, then no, the core will have used up all radioactive isotopes. No more volcanic or tectonic activity, and only residual magnetism. The continents will probably have continued to shift during the early billions of years of the journey though, as the heat that drives that process was internal.

[Noclevername]

Once the Earth gets re-illuminated and all that atmosphere and ice melts, there would be some rebound upwards from the remaining land surface*. The oceans would take far longer to thaw all the way through, and as they melted would slowly withdraw from the land as well, leading to further rebound.


*Edit: Frozen atmosphere = low erosion = still some continental land

[utesfan100]

The Earth would simply get mighty cold. And since the nearest star is 4 light years away and likely to stay there, it doesn't look like Earth will be in the viscinity of a new home star any time soon. (It would take some extraordinary motion and influence to
eject Earth from it's orbit and direct it out of system ).

The mighty cold would be after it gets mighty hot from the tidal forces on the crust. With forces strong enough to eject Earth, enough tidal heating to liquifying the crust seems reasonable.

[Xibalba]

If it gets to orbit another star, is it possible (although one in a trillion chance) that it becomes habitable once again, given it orbits at the correct distance from the star, even if this means it becomes tidally locked (because it's a dwarf star)?

It would probably not reawaken by itself, however, so let's say our own advanced civilization, at the point of the event (Earth's ejection), has crafted some plan with bio-bunkers and all to spread life once again, automatically, when (and if) the conditions are okay. Then, although terraforming Earth from zero to how it was before would be incredibly complicate, let's say computers and an army of biologists, ecologists, etc, did the programming (along with programmers, duh).

Given all this... would this still have a one in a trillion chance of being possible?

[Noclevername]

To make it sound plausible, don't go into too much detail about the specifics of the bio-bunkers. The more technobabbling you do, the more you can get wrong (a writing lesson I learned the hard way). If this is all just setting the background, you can pretty easily handwave it with "but humans had planted the seeds for their world to reawaken someday" or a similar line. If it's part of the plot, that makes it more difficult; perhaps you can get away with invoking nanotech as long as you wash your hands afterwards.

As you say it's going to be a fantasy, I don't know what if any level of the supernatural will be involved, but if you have a system of magic then that too could play a role in restoring life or balancing the still-adapting ecosystem. Or perhaps leftover nanotech is your magic...

[Swift]

Actually, I don't think you have to assume your "bio-bunkers". If it kept the "raw materials" (water, atmospheric components) and if it took up an appropriate orbit around a new star, I don't see why life couldn't start anew. Of course, this new life might not resemble the life on the Earth as we know it.

And I would guess the odds of all of that happening are very, very long. For one thing, the mechanism of capture around a new star would be difficult.

[IsaacKuo]

For the purposes of this story, the last "star" would not be a red dwarf. It would be a white dwarf. Red dwarfs evolve into white dwarfs when they run out of fusion fuel.

A white dwarf might not be a "star" by some specific definitions, because it has no active fusion powering it. However, it does glow, and it can glow with the same visible frequency spectrum peak as our own sun. In fact, a white dwarf at the right distance could look pretty much like our own Sun, producing much the same spectrum and illumination, and appearing the same size.

Now, by this era any technological civilizations will have moved on from using stars for energy. Long after the last white dwarf has cooled down, there will still be plenty of energy available around black hole systems.

[publiusr]

Gilese 710/ DM 61 366 is about as good as it gets: http://cosmoquest.org/forum/showthre...0128-DM-61-366

It was to get within .29 of one light year--but with a one light year margin of error.

[Nick Theodorakis]

This thread makes me think of the story "A Pail of Air" by Fritz Leiber.

Nick

[Noclevername]

This thread makes me think of the story "A Pail of Air" by Fritz Leiber.

Nick

Heh, I remember that one. Just don't put the bucket too close to the fire!

[Xibalba]

Noclevername : Yup, it's just to set the background of the story, so nothing really clear about this, I just want to know for myself how it was done, vaguely. Then, there's no magic or supernatural powers, because I try to stay into our reality, but the mood is kinda fantastic. Then, the civilization has rose again from some bunkers, but some others led to autocrats, dictators and monarchies, mostly violent and power-hungry, so the peaceful "scientific" populations quickly became enslaved. Then, a kind of "plague" or virus went on and killed like 99% of the people. I have to tell you that these people that awoke from the bunkers do not age, they are theoretically immortal, despite being subject to new illnesses and physical damage. Their children, however, aren't immortal, since they didn't have the medical treatment required, that doesn't exist anymore given the loss of the scientific advanced civilization. That's the background. Some scarce survivors of the plague are scattered around the Earth, and some will suicide because they think they are the only one left, but there are a few pregnant women who survived, and then gave birth to micro-tribes. These mothers being immortals, they are worshipped by their children. In the story, there is one guy who survived and didnt go insane (to some degree), he is a scientist and believes humanity must be taken to a new level, and that this can be achieved only if they melt with technology, becoming cyborgs I guess, or transhumans. He is also immortal, but realizes he must hurry since the star shows signs of exhaustion, and is indeed dying at the very beginning of the story.

IsaacKuo : I chose red dwarves because they die smoothly, which is something required for my story. If white dwarfs can also die without exploding and all, it's okay for that. If not, well I'll just say it isn't the LAST ONE star, but one of the lasts... Oh, and in a perfect world, it wouldn't go out progressively, as in diminishing the output heat and luminosity on thousands or millions of years until extinction, but rather just like stop emitting in one day. I know this might not be possible though :/ Is there any kind of star that does that?

[slang]

This thread makes me think of the story "A Pail of Air" by Fritz Leiber.

Which is available through Baen Books for free, if/when they fix their webserver. "A Pail of Air"

[IsaacKuo]

IsaacKuo : I chose red dwarves because they die smoothly, which is something required for my story. If white dwarfs can also die without exploding and all, it's okay for that.

Red dwarfs turn into white dwarfs when they "die". White dwarfs are, in a sense, already dead. They have no more fusion adding new energy into them. They just slowly get cooler and cooler as they radiate away their remaining heat. They don't explode, they just very slowly and gradually fizzle out.

An important exception is if a white dwarf is in a close binary star system, and it either collides with the other star or accumulates mass by drawing matter away from it. If a white dwarf accumulates enough mass, it can undergo a runaway carbon fusion reaction, producing a supernova.

But an isolated white dwarf will just sit there glowing like a hot coal, cooling down as it radiates away its heat.

All red dwarfs will turn into white dwarfs, unless something else external is done to them. (Like being swallowed up by a black hole, or destroyed by space aliens, or something.)

If not, well I'll just say it isn't the LAST ONE star, but one of the lasts... Oh, and in a perfect world, it wouldn't go out progressively, as in diminishing the output heat and luminosity on thousands or millions of years until extinction, but rather just like stop emitting in one day. I know this might not be possible though :/ Is there any kind of star that does that?

No.

[Jens]

For a science-fiction-based fantasy story, the Earth has been ejected from the solar system by interacting with a roaming planet from outer space. Eventually, it ends orbiting the last star, which is a red dwarf, because of the entropy of the universe. So that's quite far in the future.

One other thing is that it is in practice quite unusual for the earth to be able to go into orbit around another star, because it will start its trajectory outside of orbit, so it will normally not enter an orbit. It would probably require something like an encounter with another planet within that new system. Or giant retrothrusters, which the earth doesn't possess.

[ravens_cry]

Which is available through Baen Books for free, if/when they fix their webserver. "A Pail of Air"

Thanks for sharing; that was a beautiful story.

[kzb]

The last red dwarf star will be something in the region of 100 trillion years in the future. This is because they can last up to 10 trillion years, and many further generations are possible before all the hydrogen in the universe is consumed. Even after that, as Isaac kuo says, there are white dwarfs lasting for many billion years. If you believe current cosmology, the Big Rip will probably occur long before we are in a "last star" scenario.

On the 100 trillion-year timescale, I can only think that Earth's core would have long since cooled. The uranium and thorium would have decayed away, but there should still be deuterium available for fusion power plants.

The Pail of Air story - yes this is one of those that you read as a child or teenager, and you remember it for life. If you're going to write your new story I think you should definitely credit this in your intro.

Question: anyone know of any good papers on the "interaction probability" between stars? Around here is is evidently very small, but I do wonder about the inner galaxy. Also it should be possible to update any study with new data on brown dwarf/rogue Jovian population frequencies.

[Xibalba]

Well, seems like I'll have to read the Pail of Air thing...

Yup, it might be around a white dwarf cooling down, and yup it probably had some planets still around it for the Earth to fall into an habitable orbit, and yup the star might cool down and fade away progressively, slowly starving the plants on Eath to death.

But will the habitable region around a white dwarf will tide-lock the Earth to it? And if so, can this heat the interior of the Earth to some degree? Because before falling into tidal locking, it will probably spin a little and forces will be stretching it before it eventually stop spinning (or when revolution = rotation).

[DancesWithFruitBats]

A planet ejected from its system would stand little chance of ever falling into the pull of another. It would sail through interstellar space like a ghost ship and if near the edge of a galaxy might head into the intergalactic void with only the decay of its component atoms to look forward to.

[Xibalba]

A planet ejected from its system would stand little chance of ever falling into the pull of another. It would sail through interstellar space like a ghost ship and if near the edge of a galaxy might head into the intergalactic void with only the decay of its component atoms to look forward to.

Indeed, the chances of this happening are infinitesimal, but you will understand that sometimes, for the story's sake, chance must be manipulated to give something interesting, unlikely, but possible.

[Noclevername]

How about this: Instead of the "sun" going out, say that another body is rapidly approaching and will yank the Earth again from its new orbital home. After all, if one coincidence can happen, why not two?

Or maybe it's not a coincidence at all, maybe this is the same object that flung Eath away to begin with, and has been following the same path for all this time, loosely gravitationally bound to Earth. When Earth got caught by the white dwarf, the object got flung away, but after a long orbit now it's back and still dangerous.

[kzb]

Here's an idea: the merger of MW and M31 about a billion years in the future could end up with the solar system being flung into intergalactic space.

A solar system in intergalactic space, after many more billions of years, will eventually see all galaxies going beyond the light horizon. Cosmology as we know it will become impossible.

So here we have a scenario with Earth circling a dimming white dwarf, wandering through empty space, and the inhabitants having no clue there is anything else in the universe besides the solar system (unless they have retained knowledge from earlier epochs).

But after many billions of years, the solar system could, by chance, come within range of another out-flung system. This could be a long-lived red dwarf system.

There are two flies in this scenario (1) the inhabitants would have to survive the red giant stage of solar evolution (perhaps by moving further out in the solar system) and (2) the Big Rip could happen first.

[potoole]

This Earth being ejected from this solar system, traveling through space for hundreds of trillions of years, then being recaptured by a dying red dwarf, then being revived to life (which would probably be highly unlikely). Well, I don't get the point.

What would be the purpose of the story? Would it be so that humans, or some intelligence, would be around to witness the end of the universe? But, even at that, there would still be trillions of years left until universe's end. If it would be possible for any kind of intelligence to witness such an event.

Put a group of humans aboard a spaceship that continuously, and out of control, approaches the speed of light. As they approach that speed, universal time progesses faster and faster, with trillions of years passing by, until the humans bring the spacecraft under control. By then they have reached the end times of the universe, and have witnessed its dying. Oh, but that story has already been written bu Poul Anderson.

Sorry, I had no intention of being criticle or sarcastic.

PO'T

[Noclevername]

This Earth being ejected from this solar system, traveling through space for hundreds of trillions of years, then being recaptured by a dying red dwarf, then being revived to life (which would probably be highly unlikely). Well, I don't get the point.

Xibalba hasn't described the plot, that's just the setting so far.

[Drunk Vegan]

I don't have much to add beyond what others have already said, but I just thought you should know that many of your themes are similar or related to ones that Vernor Vinge has explored in his books, and I think you would benefit greatly from reading his work if you haven't had a chance to yet. He's one of the few contemporary science fiction authors that I can honestly say produces masterpieces almost every time.

[Xibalba]

This Earth being ejected from this solar system, traveling through space for hundreds of trillions of years, then being recaptured by a dying red dwarf, then being revived to life (which would probably be highly unlikely). Well, I don't get the point.

What would be the purpose of the story? Would it be so that humans, or some intelligence, would be around to witness the end of the universe? But, even at that, there would still be trillions of years left until universe's end. If it would be possible for any kind of intelligence to witness such an event.

Put a group of humans aboard a spaceship that continuously, and out of control, approaches the speed of light. As they approach that speed, universal time progesses faster and faster, with trillions of years passing by, until the humans bring the spacecraft under control. By then they have reached the end times of the universe, and have witnessed its dying. Oh, but that story has already been written bu Poul Anderson.

Sorry, I had no intention of being criticle or sarcastic.

PO'T

Well the plot is not about the universe's end at all... in some way. Because the civilization has regressed to a state where writing in "fantasy mode" is correct, even if the story is way in the future, there will be no direct talk about the ending of the universe.

Also, in the background plot, I imply that the universe will not "die" by Big Rip, but by Entropy... Then, being the last star, or practically the last one, the last scientist remaining on Earth, living outside the now-middle-ageian civilization, hopes to outlive the universe by "crystalianizing" his own brain, so that, like in a recent article on UT, the crystal can live and function actually after the universe death. Of course, he isn't experimenting on himself, but on "scientific prisoners" he abducts from local "tribes" or villages... Many die, and those who survive aren't successful realizations either...

But one of them, after its release, proves to be THE working formula, so he lures him into coming back so he can further analyze him and all and all...

At this point, the sun has dimmed to a point where photosynthesis isn't working anymore, and that is the end of the viable universe... He wants to outlive the universe, being truly immortal... but [SPOILER]doesn't succeed.[/SPOILER]

You have to take into account that there are remaining immortal humans... they got medically treated when the civilization was at its best, but a pandemy of some sort eradicated like 99% of the humans, and there was the fall of the civilization, its degeneration into medievalism, and the cult of the immortal men who were worshipped as Gods... The previous goal of our last scientist was to banish the cult of those false Gods, as, for him, only science is worthy, and so he went into a crusade to kill the Gods, and his person was feared by all humans on the Earth. Note that the humans that were born after the fall of the civilization didn't benefit the medical advantages and hence are subject to the effects of aging... Then, when he noticed the sun was dimming (yeah, on thousands and thousands of years but hey he's immortal!) he promptly made researches on the crytalization of the human brain... there is our storyline

Everything told in a musical un-comedy format.

Hope you enjoy

[IsaacKuo]

In such a science-poor society, it's more plausible for the end to come from some sort of disaster or some boring typical reason for species extinction, long before the gradual dimming of a white dwarf. The timescale of this dimming--many billions of years--is far longer than the lifespan of the typical Earth species. (Heck, it's far longer than the existence of Earth life in general.)

[onomatomanic]

But will the habitable region around a white dwarf will tide-lock the Earth to it? And if so, can this heat the interior of the Earth to some degree? Because before falling into tidal locking, it will probably spin a little and forces will be stretching it before it eventually stop spinning (or when revolution = rotation).

Interesting case. From the wikipedia article, an average white dwarf has a mass of ~0.6 M_sun and a radius of ~0.015 R_sun. If we want it to have the same effective temperature as the Sun, and Earth to end up with the same insolation, then the size a of the orbit is determined by the scaling relation

R_sun^2 / (1 AU)^2 ~ (0.015 R_sun)^2 / a^2 ===> a ~ 0.015 AU ~ 2*10^9 m

which is only five times the distance to the Moon. Tidal forces depend on mass and the inverse cube of distance, which gives us in terms of the lunar tidals:

F_tidal ~ ((1.2*10^30 kg)/(7*10^22 kg)) / 5^3 F_tidal|lunar ~ 1.5*10^5 F_tidal|lunar

Instead of a tidal bulge on the order of a metre, it would be on the order of 100 km. Meaning that until tidal lock is achieved, the only permanent bodies of water would be lakes with sufficiently steep sides. Anything with shallow sides, including the oceans, would lose its water to two big blobs which would do their best to remain stationary with respect to the new sun while the planet rotates along underneath them. I guess life better stays in those sealed bunkers for the duration. The ordinary scaling law for time to tidal lock is something like

T_lock ~ (10^10 years) / ((T_rot in days) (F_tidal/F_tidal|lunar)^2) ~ (1 year) / (T_rot in days)

where T_rot is the original (unlocked) day-length with respect to the tide-inducing body. Unless Earth spins a lot faster upon capture than it does now, the result is on the order of 1 year. If, on the other hand, Earth spins a lot slower, which seems like the more likely scenario to me, then the day-length would be mainly determined by the year-length, which works out on the order of 1 day (as in 24 hours), funnily enough.

Mind you, I'm not sure if this situation might not be too extraordinary for the scaling relation to apply in that form. It assumes that the combination of atmospheric and ocean tides and planetary deformation is sufficient to actually dissipate rotational energy into heat at the maximal rate, which seems questionable. Assuming that it does, the power output would be vast:

P_tidal ~ E_rot / T_lock
P_tidal ~ (1/2 I w^2) / ((1 year) / (T_rot in days))
P_tidal ~ (1/2 (2/5 M R^2) ((2 pi)/T_rot)^2) / ((1 year) * (1 day) / T_rot)
P_tidal ~ (7 * (6*10^24 kg) * (6*10^6 m)^2) / ((3*10^7 s) * (10^5 s) * T_rot)
P_tidal ~ (5*10^26 kg m^2 / s^2) / T_rot
P_tidal ~ L_sun / (T_rot in seconds)

I'm not sure where all these numerical coincidences come from, but that aside, it does give one quite a good sense of scale: The Earth has about one ten-thousandth the surface of the Sun, and T_rot should be on the order of one hundred thousand, so for the Earth to dissipate that amount of power, it would have to output only one order of magnitude less power per unit surface than the Sun does. Since black-body power output scales with T^4, that means more than half the temperature of the sun. And as rock begins to melt by as little as 1,000 K, this would directly liquify the upper portions of the planet. Assuming the interior has been frozen solid in the interim, one ends up with a sort of inverted planet whose surface is hotter than its core. In the long run, what is of more practical import is that this might just be hot enough to boil away (away as in all the way into space) all of our water, even in as little as that one year we're talking about.

As I said, the planet might well not actually have the capacity to dissipate power at that rate, so things might not get quite that bad. The price for that, though, would be a longer time to lock, so the not-quite-that-bad conditions would last a lot longer. Conclusion: Unless the planet is already as close as no matter to tidal lock when it assumes a habitable-zone orbit, which seems highly unlikely, the process of locking it would pretty much make it uninhabitable... Catch-22. The only upside I see is that this might indeed just about do what you were hoping for, in the long run, and kick-start the planet's dormant geological activity again.