## Blackholes: Accretion Vs Expulsion

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BDanielMayfield
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### Re: Blackholes: Accretion Vs Expulsion

Doum wrote:Ohh by the way Chris,

i do get the same speed (1513 km/s) if i do the calcul the same way you did. i am trying not to think of all the attempt i make with excel to have the final speed of encounter between the 2 bodies.
And earlier...
Doum wrote:My excel table worth nothing.

ohhh, i'm hurt somewhere above my shoulder. is that a black hole.
Yea, information do get lost in a black hole.
You have experienced the agony of the brute force method Doum. Don't be too hard on Excel. Just imagine how hard your pre-calculus method would have been without a computer

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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:
neufer wrote:
But gas velocities are only ~250 km/s even at the heart of the Sun
so the Sun would be hard pressed to satiate the BH at its full capacity (except, perhaps, at its heart).
But that would be the Sun's normal internal state without a 5 solar mass BH plunging through its heart. During this period the whole internal physics of the Sun would be changed, because the whole Sun would briefly act as if it was a 6 solar mass star undergoing core collapse. This should be a real bear of a problem to model accurately, as Chris has pointed out.
Indeed

The temporary nature of the event makes it very difficult to evaluate.

The accelerations at the edge of the BH "drill hole bubble" are very strong (~ 30 million km/s2 )
but these (~millisecond) forces appear to be primarily involved with closing up the bubble rather than feeding the black hole itself.

I haven't even begun to consider:
• 1) how the Sun's large scale vibrational modes are affected by such a strong but temporary twanging

2) or how much material is torn away from the Sun (probably many times the amount the BH swallows as Chris suggests).
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### Re: Blackholes: Accretion Vs Expulsion

So as Bruce said ,

A less catastrophic, plausible outcome could also involve the inflation of the Sun into a short Red Giant phase, possibly with planetary neubula discharge before the Sun settles back onto the main sequence. Hay y'all, this could even have a bright side: If a reduced massed Sun survives it might stay on the MS for a few more billions of years! The Sun will have had a life extending makeover.

Doum: Gee i have problem with the use of quote. Sorry:

-It might be what will happen. Unless the sun go pouf!!! Rob, i am not sure that a life habitat near neptune will be safe now. It might be better to go to another star as you said. But a 4000 km/s black hole initial speed being at a 1000 UA (150E12 meters) from the sun will take 434 days to travel. Not counting the acceleration the 2 bodies get from their mutual gravity. So it will take less days then that. It aint enough to escape the drama. Even at an initial speed of a 1000km/s, it still will take about 4.75 years for the black hole to get to the sun. Still not enough. At a 100 km/s it will take 47.5 years for the 2 bodies to meet. That might be enough to build a spaceship and get the hell out. But it still seem short in time.

im not sure my calcul is right. But checking and rechecking i still get those number.

PS: 4000 km/s= 4 000 000 m/s initial speed
1000 AU= 150E12 meters
i got the answer in seconds. so /60/60/24 and if needed /365

Now im wondering, is it possible for a black hole to only have an initial speed of only a 100 km/s when it is at a 1000 AU from the sun? Is it a common speed?

Bruce, black hole do evaporate i am ok now. i think !!?

BDanielMayfield
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### Re: Blackholes: Accretion Vs Expulsion

Doum wrote:Now im wondering, is it possible for a black hole to only have an initial speed of only a 100 km/s when it is at a 1000 AU from the sun? Is it a common speed?

Bruce, black hole do evaporate i am ok now. i think !!?
Glad you've recovered now Doum. Sure, a 100 km/s speed is possible. It should even be more likely than the 1000-5000 km/s initial speeds we've been discussing. But the slower the passage thru the system and the Sun the greater the damages would be.

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### Re: Blackholes: Accretion Vs Expulsion

Ok, but a black hole coming from an infinite distance toward the sun at an initial velocity of 0 km/s will give an impact speed of 1512 km/s ( Chris calculation and i almost got the same result (1513 km/s)). Wich is close to neufer 500 billions cubic km of of the sun volume remove in around 600 seconds (less then that i think). A 100 km/s initial speed will also reduce that amount a bit.

Rob make sure your black hole dont come too fast if you want your people to escape the drama. Or if you want them to scream for a longer time.

BDanielMayfield
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### Re: Blackholes: Accretion Vs Expulsion

neufer wrote:I haven't even begun to consider:
• 1) how the Sun's large scale vibrational modes are affected by such a strong but temporary twanging

2) or how much material is torn away from the Sun (probably many times the amount the BH swallows as Chris suggests).
Your second point takes us back to how much mass does the Sun lose during the event. It also could add an accretion disk and jets to Rob's tall tale.

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### Re: Blackholes: Accretion Vs Expulsion

Agreed.

im eager to see how the story will go. I wonder what space engine Rob's tale noahh ark is using to escape. Usual chemical deflagration rocket (like now), chemical explosion engine, nuclear solid core or liquid core or gazeous core engine. Micro explosion of fusion reaction (a few hundred time a second. That might give a few percent of light speed to escape)
Or better, an EMdrive. That thing that make scientist go crazy against it. For a sci-fi book it might work untill proven it dont work.

Story will tell.

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### Re: Blackholes: Accretion Vs Expulsion

Doum wrote:... I wonder what space engine Rob's tale noahh ark is using to escape. Usual chemical deflagration rocket (like now), chemical explosion engine, nuclear solid core or liquid core or gazeous core engine. Micro explosion of fusion reaction (a few hundred time a second. That might give a few percent of light speed to escape)
Or better, an EMdrive. That thing that make scientist go crazy against it. For a sci-fi book it might work untill proven it dont work. ...
That depends on how far into the future I decide to push the tale, and that depends on how plausible any kind of survivability is if such an event were to happen in the near future. I want the survivors to have at least a little bit of a chance.

One of the conventions of science fiction is to use things already invented -- to have, in a sense, a common future history at least as far as technology goes. So I can use a type of multi-generation ship and its propulsion system that others have already suggested. There's plausible forms of such things all over the web, with good background calculations and discussions of likely time frames to develop them. And as we've seen in the past, humans tend to develop new technology a lot faster under duress than they do in calmer circumstances.

One key plot element is exactly that sort of discussion: what propulsion systems are available, how quickly can any other system be developed, how quickly can they be improved, and therefore how many people can be taken off the planet and for how long. The results of that kind of discussion will determine where the survivors try to go. I can't see getting more than a thousand or so going to another stellar system, but perhaps tens of thousands could hang out in relatively safe zones of the Solar System for years and perhaps decades. Would that be long enough to find a livable home? Don't know yet. Lots to think about!

Rob

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### Re: Blackholes: Accretion Vs Expulsion

rstevenson wrote:One key plot element is exactly that sort of discussion: what propulsion systems are available, how quickly can any other system be developed, how quickly can they be improved, and therefore how many people can be taken off the planet and for how long. The results of that kind of discussion will determine where the survivors try to go. I can't see getting more than a thousand or so going to another stellar system, but perhaps tens of thousands could hang out in relatively safe zones of the Solar System for years and perhaps decades. Would that be long enough to find a livable home? Don't know yet. Lots to think about!
One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
Chris

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### Re: Blackholes: Accretion Vs Expulsion

Okay, now it's a trilogy!

Rob

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### Re: Blackholes: Accretion Vs Expulsion

Chris Peterson wrote:
One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
But we'll be able to see the black hole coming in time...right
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### Re: Blackholes: Accretion Vs Expulsion

neufer wrote:
Chris Peterson wrote:
One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
But we'll be able to see the black hole coming in time...right :?:
In the real world, we might not. But in a work of fiction, it would certainly be possible to construct a realistic scenario proving any amount of advance warning required to support the story. Need 100 years warning? Make the initial detection by observing some sort of anomaly in a nearby binary star system, or an orbital anomaly in a nearby planetary system. Or take advantage of observing a chance microlensing event. We might even detect it decades in advance by simply noticing that our own planets are not where they are supposed to be. We have exquisitely complex and accurate numerical models for predicting planetary positions, and a deviation in orbital elements quite a few decimal places out would become quickly apparent.
Chris

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### Re: Blackholes: Accretion Vs Expulsion

Chris Peterson wrote:
rstevenson wrote:One key plot element is exactly that sort of discussion: what propulsion systems are available, how quickly can any other system be developed, how quickly can they be improved, and therefore how many people can be taken off the planet and for how long. The results of that kind of discussion will determine where the survivors try to go. I can't see getting more than a thousand or so going to another stellar system, but perhaps tens of thousands could hang out in relatively safe zones of the Solar System for years and perhaps decades. Would that be long enough to find a livable home? Don't know yet. Lots to think about!
One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
All very interesting ideas. In such a do or die situation the old adage "don't put all your eggs in one basket" would apply. If jets were to form, (and wouldn't they have to, because the BH coming out from the Sun sporting an extremely hot, large accretion disk would be a given, wouldn't it?) then "jet sailing" away might be possible, if the right place to be could be predicted.

Bruce
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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:
Chris Peterson wrote: One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
All very interesting ideas. In such a do or die situation the old adage "don't put all your eggs in one basket" would apply. If jets were to form, (and wouldn't they have to, because the BH coming out from the Sun sporting an extremely hot, large accretion disk would be a given, wouldn't it?) then "jet sailing" away might be possible, if the right place to be could be predicted.
I think it is unlikely that jets would form. And if they did, I think that's the last place you'd want to be, given the very high energy radiation that jets are known to produce. It is, after all, jets which create the primary risk to nearby star systems in the event of a supernova.
Chris

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### Re: Blackholes: Accretion Vs Expulsion

Chris Peterson wrote:
We might even detect [an approaching BH] decades in advance by simply noticing
that our own planets are not where they are supposed to be.
Tidal forces drop off very rapidly with distance

By my calculation we would have to both calculate & measure the locations of our own planets/spacecraft
to an accuracy of ~50 meters in order to detect a BH that was even just one parsec away.

However, we only have to both calculate & measure the locations of our own planets/spacecraft
to an accuracy of ~50 kilometers in order to detect a BH that was 0.1 parsecs away.

This is within our current capabilities and still gives us a heads up time of ~1,000 years.
Last edited by neufer on Thu Mar 23, 2017 8:09 pm, edited 1 time in total.
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### Re: Blackholes: Accretion Vs Expulsion

Chris Peterson wrote:
neufer wrote:But we'll be able to see the black hole coming in time...right
In the real world, we might not. But in a work of fiction, it would certainly be possible to construct a realistic scenario proving any amount of advance warning required to support the story. Need 100 years warning? Make the initial detection by observing some sort of anomaly in a nearby binary star system, or an orbital anomaly in a nearby planetary system. Or take advantage of observing a chance microlensing event. We might even detect it decades in advance by simply noticing that our own planets are not where they are supposed to be. We have exquisitely complex and accurate numerical models for predicting planetary positions, and a deviation in orbital elements quite a few decimal places out would become quickly apparent.
Here's a way to make the first discovery very current: The Gaia mission data reveals a subtle pattern in the motions of several nearby stars in the direction of one of the Sun's poles. Something unseen is deflecting them ...

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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:Here's a way to make the first discovery very current: The Gaia mission data reveals a subtle pattern in the motions of several nearby stars in the direction of one of the Sun's poles. Something unseen is deflecting them ...
Bruce
That reminded me of a Ray Bradbury story, I thought. Sure enough...
Something Wicked This Way Comes is a 1962 dark fantasy novel by Ray Bradbury. It is about 13-year-old best friends, Jim Nightshade and William Halloway, and their nightmarish experience with a traveling carnival that comes to their Midwestern town one October. The carnival's leader is the mysterious "Mr. Dark" who seemingly wields the power to grant the citizenry's secret desires. In reality, Dark is a malevolent being who lures these individuals into binding themselves in servitude to him.
I think I'm going to have to incorporate a reference to Something Wicked This Way Comes somehow. Perhaps I can use it as a chapter heading without causing offence to Bradbury's heirs. And how about that Mr. Dark? I think one of my characters is going to have to be a Bradbury fan.

Rob

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### Re: Blackholes: Accretion Vs Expulsion

On the matters of first contact timing and the duration of the BH being inside the Sun we've just been considering the Sun's radius as it is now, approx. 7e5 km. This wouldn't be correct due to tidal stretching. Spaghettiffication of the Sun would prolong and increase the hole's effects on the Sun during the transit. Interestingly, spaghettiffication would occur on the way in and on the way out, but it would be zero in the middle. So, depending on the velocity of the encounter, the Sun would stretch into an American football shape, become a smaller sphere than it is now, and then become football shaped again as the BH leaves. As it exits the inner solar system the Sun would return to being spherical.

Shrinkage of the Sun's equatorial radius during the event would also increase its rotation rate. After the event the smaller Sun should have an increased rotation rate. I'd guess that magnetic activity on the Sun's surface would be much increased as well.

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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:... the Sun would stretch into an American football shape, become a smaller sphere than it is now, and then become football shaped again as the BH leaves. As it exits the inner solar system the Sun would return to being spherical. ...
The atmosphere of the Sun -- and perhaps its core too -- should be treated as fluids in our discussions and calculations. I imagine they would rebound from all this reshaping you mention, with the polar regions alternately expanding outwards and shrinking inwards for years to come, gradually settling down to a steady state.

Rob

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### Re: Blackholes: Accretion Vs Expulsion

rstevenson wrote:
BDanielMayfield wrote:... the Sun would stretch into an American football shape, become a smaller sphere than it is now, and then become football shaped again as the BH leaves. As it exits the inner solar system the Sun would return to being spherical. ...
The atmosphere of the Sun -- and perhaps its core too -- should be treated as fluids in our discussions and calculations. I imagine they would rebound from all this reshaping you mention, with the polar regions alternately expanding outwards and shrinking inwards for years to come, gradually settling down to a steady state.

Rob
The whole Sun should be treated as (and is) a fluid, or conventional (consensus!) nuclear astrophysics is wrong, I think.

Indeed Rob, the Sun should be quite variable for some time before settling down as a less massive, less luminous but more magnetically active star.

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### Re: Blackholes: Accretion Vs Expulsion

rstevenson wrote:
BDanielMayfield wrote:... the Sun would stretch into an American football shape, become a smaller sphere than it is now, and then become football shaped again as the BH leaves. As it exits the inner solar system the Sun would return to being spherical. ...
The atmosphere of the Sun -- and perhaps its core too -- should be treated as fluids in our discussions and calculations. I imagine they would rebound from all this reshaping you mention, with the polar regions alternately expanding outwards and shrinking inwards for years to come, gradually settling down to a steady state.
Maybe. But it's still unclear just what the magnitude of the actual distortion would be, and there are a number of scholarly papers which discuss both hydrodynamic and magnetic damping in the Sun (and other stars) which suppress natural harmonic vibrations. The Sun might settle back into a sphere very quickly.
Chris

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### Re: Blackholes: Accretion Vs Expulsion

A little more on the oscillations the Sun might experience after the main event. I wouldn't think that the poles would pulsate up and down much after the BH, but the whole Sun could go into a variable phase while it hunts for balance and stability. All stable, constant brightness stars have an internal balance between gravitational contraction and heat from fusion in the core. But in this scenario the balance has just been upset horribly. As the BH leaves even though the sun has lost mass it should have gained a lot of internal heat, causing the Sun to puff up, like Red Giants do. But then the core cools below the fusion threshold and it will shrink, until compressional heating kicks off fusion again, causing expansion, contraction ... It could take a long time for this to settle out.

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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:A little more on the oscillations the Sun might experience after the main event. I wouldn't think that the poles would pulsate up and down much after the BH, but the whole Sun could go into a variable phase while it hunts for balance and stability. All stable, constant brightness stars have an internal balance between gravitational contraction and heat from fusion in the core. But in this scenario the balance has just been upset horribly. As the BH leaves even though the sun has lost mass it should have gained a lot of internal heat, causing the Sun to puff up, like Red Giants do. But then the core cools below the fusion threshold and it will shrink, until compressional heating kicks off fusion again, causing expansion, contraction ... It could take a long time for this to settle out.
It could. Or, the actual disruption might be minimal and little mass lost. Or, the fusion could stop and restart again in one oscillation cycle lasting just a few hours.

On the one hand, all this uncertainty allows the author a fair degree of flexibility. On the other, it means there's a good chance that any proposed scenario will be wrong, and possibly demonstrated to be so not long after publication.
Chris

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### Re: Blackholes: Accretion Vs Expulsion

Chris Peterson wrote:
BDanielMayfield wrote:
Chris Peterson wrote: One thing to think about... since the primary problem will not be the black hole, and probably not what it does to the Sun, but rather, what it does to the planetary orbits before and after the passage, there are opportunities worth exploring. For instance, a careful analysis well in advance could identify where some of the planets will end up. This could lead to colonization decisions, decisions about where to park space-based stations, and even interesting possibilities for spacecraft trajectories (e.g. Saturn and Jupiter will cross orbits while they are quite near each other, allowing for an extreme slingshot maneuver that could send the ark ship out of the system at a much higher speed than would otherwise be possible with available propulsion systems). Another option? Earth or Mars will be completely ejected from the system, making the need for an ark spacecraft unnecessary. Rather, the effort would go into making an ark planet: finding a way to enclose cities or build vast underground cities such that a substantial percentage of humans could be saved.
All very interesting ideas. In such a do or die situation the old adage "don't put all your eggs in one basket" would apply. If jets were to form, (and wouldn't they have to, because the BH coming out from the Sun sporting an extremely hot, large accretion disk would be a given, wouldn't it?) then "jet sailing" away might be possible, if the right place to be could be predicted.
I think it is unlikely that jets would form. And if they did, I think that's the last place you'd want to be, given the very high energy radiation that jets are known to produce. It is, after all, jets which create the primary risk to nearby star systems in the event of a supernova.
OK then, jet sailing is dead, or a way to get dead. Geting hit or grazed by an unexpected jet could be a falure mode plot development. To add realism, not all of Rob's 'rag tag, refuge fleet' are gonna make it.
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### Re: Blackholes: Accretion Vs Expulsion

BDanielMayfield wrote:
Chris Peterson wrote:
BDanielMayfield wrote: All very interesting ideas. In such a do or die situation the old adage "don't put all your eggs in one basket" would apply. If jets were to form, (and wouldn't they have to, because the BH coming out from the Sun sporting an extremely hot, large accretion disk would be a given, wouldn't it?) then "jet sailing" away might be possible, if the right place to be could be predicted.
I think it is unlikely that jets would form. And if they did, I think that's the last place you'd want to be, given the very high energy radiation that jets are known to produce. It is, after all, jets which create the primary risk to nearby star systems in the event of a supernova.
OK then, jet sailing is dead, or a way to get dead. Geting hit or grazed by an unexpected jet could be a falure mode plot development. To add realism, not all of Rob's 'rag tag, refuge fleet' are gonna make it.
Edit: unless Rob wants it that way. Which critics would call sappy.
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