The sun goes nova

[Swindle1984]

Several questions for a story I'm working on; related to the O'Neill cylinder thread.

1) What sort of event could cause Earth's sun to go nova?

2) Once it began to go nova, how quickly could we detect it with modern technology? Hypothetical near-future technology? In the scenario, Earth has (somewhat) gotten its shit together and is cooperating to build O'Neill cylinders and mine resources from the rest of the solar system due to a big scare over a near extinction-level comet impact; they've focused on getting their eggs out of one basket and are warily watching the sky for more doomsday objects, since the comet took them by surprise and a big piece of it is due to come back in a century or so. So they're watching the sky, but not necessarily the sun.

3) Once it began to go nova, how long would it take before heat/radiation rendered Earth uninhabitable? What about the same around, say, Jupiter?

4) Is there a good table for converting g's of acceleration into % of lightspeed and figuring how fast something would be going at a given acceleration at a given point in an interstellar STL journey?

[Junghalli]

4) Is there a good table for converting g's of acceleration into % of lightspeed and figuring how fast something would be going at a given acceleration at a given point in an interstellar STL journey?

1 G = 9.81 m/s^2 (meaning every second your speed increases by 9.81 m/s). From there figuring out the final speed is easy: just multiply by number of G and number of seconds. It gets a little tricker with relativistic velocities because relative to (relatively) slow moving reference points your acceleration will slow down as you approach c*, I guess the easiest way to do it would probably be solve the relativistic and conventional KE equations** for the same speed and divide the acceleration by the difference. As I remember from trying that myself the difference doesn't get huge until you get into quite high fractions of c, so if you can sustain 1 G acceleration for a year or so you should be able to get up to a high fraction of c.

* This is probably mangling the actual physics horribly but for purposes of a question like this it should give you a fairly decent idea of what you need to worry about.

** They are, respectively:

KE = ((1/square root(1-(velocity^2/speed of light^2)))-1)(mass of object)(speed of light^2)

KE = 1/2(mass of object)(velocity^2)

Edit: oh yes, units of mass and velocity should be (respectively) kg and m/s.

[Lord of the Abyss]

Several questions for a story I'm working on; related to the O'Neill cylinder thread.

1) What sort of event could cause Earth's sun to go nova?

Something pretty extreme, like another star impacting and merging with it. Sun-sized stars don't go nova; its mass would need to be greatly increased.

3) Once it began to go nova, how long would it take before heat/radiation rendered Earth uninhabitable?

Since stars become red giants long before they nova, if the Sun was even capable the answer would be "Earth was rendered molten about 100,000 years ago".

[starslayer]

1) What sort of event could cause Earth's sun to go nova?

It would have to be a compact star like a white dwarf, neutron star, or black hole colliding with it. Anything else just creates a larger star.

2) Once it began to go nova, how quickly could we detect it with modern technology? Hypothetical near-future technology?

8 minutes, the light travel time between Earth and the Sun.

3) Once it began to go nova, how long would it take before heat/radiation rendered Earth uninhabitable? What about the same around, say, Jupiter?

8 minutes after the nova; i.e., right when the enormous gamma and X-ray pulse gets there; the rush of particles/remains of the Sun will get there about 8 minutes later than that, and destroy the Earth. For Jupiter, this will again be light travel time, or about 45 minutes for the light, then another 45 for the gas following behind to reach and destroy the planet.

A couple of disclaimers; one, the neutrinos might get there before the light, since the photons have to fight their way through the Sun, while neutrinos zip right through; this might also lengthen the time Earth has remaining, as we may see the Sun visibly expand before the initial radiation pulse hits. Still, it won't be much time, and everything in the Solar System will die a quick death.

[sirocco]

1) What sort of event could cause Earth's sun to go nova?

It would have to be a compact star like a white dwarf, neutron star, or black hole colliding with it. Anything else just creates a larger star.

The effects such a body will have on its surroundings will be visible from far away. And it will be relatively slow compared to the revolution of the planets around the sun. Either its gravity field will severely disrupt the smaller planets (like Earth) or it will just crush some of our neighbors on its way to our star. Whatever the case, I think the sun going nova will be the very last of our worries.

I see Armageddon+2012+Sunshine movies happening all at the same moment.

If your story is soft scifi, you can surely be more creative.

3) Once it began to go nova, how long would it take before heat/radiation rendered Earth uninhabitable? What about the same around, say, Jupiter?

8 minutes after the nova; i.e., right when the enormous gamma and X-ray pulse gets there; the rush of particles/remains of the Sun will get there about 8 minutes later than that, and destroy the Earth. For Jupiter, this will again be light travel time, or about 45 minutes for the light, then another 45 for the gas following behind to reach and destroy the planet.

A couple of disclaimers; one, the neutrinos might get there before the light, since the photons have to fight their way through the Sun, while neutrinos zip right through; this might also lengthen the time Earth has remaining, as we may see the Sun visibly expand before the initial radiation pulse hits. Still, it won't be much time, and everything in the Solar System will die a quick death.

And we probably would be long gone before all that.

[dworkin]

1) What sort of event could cause Earth's sun to go nova?

Becoming a white dwarf is usually the first step, being a binary is another

2) Once it began to go nova, how quickly could we detect it with modern technology?

A Mk1 eyeball should suffice. At most a telescope and maybe a spectroscope would be needed. I give us several million years warning at the minimum.

3) Once it began to go nova, how long would it take before heat/radiation rendered Earth uninhabitable? What about the same around, say, Jupiter?

Given the requisites they earth may well already be uninabitable to all but the most enthusiastic astronomers.

Novae and their often confused cousins the helium (and higher) flash are part of the long term, highly predictable stages of stellar evolution.

[Swindle1984]

Ok, so a nova is out. I thought as much.

What sort of disaster could plausibly happen that would require us to begin efforts to evacuate the solar system within twenty years?

[Batman]

Somebody doing it on purpose. The sun going nova via accidental natural disasters as mentioned in this thread is not only unlikely as hell but something that even with modern day technology we'd see coming for millenia.
Even if we go with the sun turning into a Red Giant (which it's actually going to eventually, without hopelessly unlikely to occur naturally celestial accidents) Earth will still be destroyed but again with eons of warning.
The only way we'd only get only a few decades worth of warning is if somebody with seriously advanced technology (well by our standards anyway) saw to it happening.

[dworkin]

A near miss by a stellar object through the oort cloud causing 'mass bombardment' by all the disturbed objects could qualify. If you wanted to be spiffy make it the wake of a FTL ship merely going somewhere else.

[Uncluttered]

Somebody doing it on purpose. The sun going nova via accidental natural disasters as mentioned in this thread is not only unlikely as hell but something that even with modern day technology we'd see coming for millenia.
Even if we go with the sun turning into a Red Giant (which it's actually going to eventually, without hopelessly unlikely to occur naturally celestial accidents) Earth will still be destroyed but again with eons of warning.
The only way we'd only get only a few decades worth of warning is if somebody with seriously advanced technology (well by our standards anyway) saw to it happening.

This is all true.
We have a good idea on how stellar evolution works. Most of the refinements of the model are plasma physics to more accutately estimate mass loss.

Our sun is too small for any type of nova by itself. To my knowledge, our local group is a stable bunch. However, there is nothing stopping a rogue black hole from plowing through the neighborhood. Instead of killing off old Sol, how about wacking a nearby star,

I say this, because it looks like you need a stellar based diaspora for your plot.

You could always use the cliche "science experiment gone wrong". Please don't. Scientists usually don't perform experiments that have reasonable chances of destroying the sun. Our job is hard enough without public mistrust.

What about an attack from ET? Fermi solved because interstellar assholes drop black holes into other peoples stars.

A black hole with the mass of Ceres should have a mouth big enough to gobble hydrogen.
Contain it with an electrostatic charge.
Hawking radiation, focused with a reflective shell, would make the blackhole a pretty good interstellar engine too.
Aim.
Fire.
Eat the star.
Nova.

[SeaTrooper]

Several questions for a story I'm working on; related to the O'Neill cylinder thread.

1) What sort of event could cause Earth's sun to go nova?

Are you talking about enemy action here? Our sun isn't big enough to go nova, so some external influence would be required. Worse, stars that are large enough typically become red giants prior to the final collapse, and that is also a factor of their size/mass. Frankly, you would need some serious handwavium to achieve this.

[Ariphaos]

Ok, so a nova is out. I thought as much.

What sort of disaster could plausibly happen that would require us to begin efforts to evacuate the solar system within twenty years?

A small rogue black hole moving at exceptionally high speed, on direct collision course with the Sun. Still going to look implausible as heck, but hey.

[keen320]

Maybe say that they discover evidence that the near miss comet wasn't an accident? That it was the first attempt by somebody to get rid of us but they screwed it up/some implausibly secret government agency stopped it and didn't tell anyone so as to not cause a panic (not recommended)/one of them had second thoughts and warned us after stopping the first attempt/ it was only a trial run. Then they find out the aliens figured out what went wrong or whatever but they only have STL so we have a small breather to take advantage of before they try something more sure to kill us.

[CaptainChewbacca]

If FTL communication exists, we could be aware of a Gamma Ray Burst heading our way with a few decades of warning. That's something you definitely want to avoid.

[Sarevok]

Even if we do evac the Sol system there is no need to immedietly head to Alpha Centauri or beyond. Plenty of oort cloud bodies and rogue planets in the dark depths of interstellar space for resource and energy needs.

[sirocco]

I think that for ET the cheapest way would be to divert the course of some asteroids towards Earth. It won't be a disaster since we could always blow them up but I recall a recent event where an asteroid went unnoticed between Earth and the Moon. There will be limits to our capacity to protect the population.

With such thing going public, governments will start building space stations for A-defense and B- start building O'Neill like ships just in case. They will probably also pack some weapons to give ET a 'warm' welcome.

if ET uses STL travel, they will probably come at full force like ID4 and Earth would probably just have time to build only a small fleet and probably around the gas giants to be able to mine helium from them and ore from the asteroids. Their own gravity field may provide also protection from whaatver ET launches at us.

[Swindle1984]

Maybe say that they discover evidence that the near miss comet wasn't an accident? That it was the first attempt by somebody to get rid of us but they screwed it up/some implausibly secret government agency stopped it and didn't tell anyone so as to not cause a panic (not recommended)/one of them had second thoughts and warned us after stopping the first attempt/ it was only a trial run. Then they find out the aliens figured out what went wrong or whatever but they only have STL so we have a small breather to take advantage of before they try something more sure to kill us.

This is an idea. I was planning on leaving aliens out because I wanted the story to be soft enough to appeal to people, but look like a hard sci-fi story. Basically, introduce casual readers to the concept that hard sci-fi might just be accessible enough to enjoy.

But, it sets up a couple possibilities.

I'd already decided that a rogue comet pancaking part of the planet would scare people shitless and there were would be incessant demands that we "do something"; somebody mentions the O'Neill cylinder space habitat as a way of getting us off of Earth and the media and public latch onto it, and the politicians go along with it because they'd like to remain employed.

Fifty years later, there's a dozen or so pairs of cylinders around Earth's lagrangian points, and we're beginning to colonize the areas around Mars, the Belt, and Jupiter so we can mine them for resources. People on Earth have gotten over the craze and are bitching about the expense of building cylinders and supporting them, having forgotten the threat of the comet that will eventually return and possibly hit Earth again, this time with the majority of its mass. Most of Earth is run by a UN-style organization (but with more power) and society is soft and run by a well-meaning but despotic far-left socialist government. Because of concern for the environment, most manufacturing and mining is left to the space habs, roughly half of which are dominated by right-wing or libertarian capitalists (who either left to live by their own rules, or got shipped off so they'd stop being a pain in the ass on Earth.) who are pissed at having to operate under Earth's rules when they "do all the work". This leads to one set of colonies getting fed up with an import/export tariff system and other regulations and declaring independence; Earth's attempt to assert dominance via an embargo and half-assed military takeover results in orbital bombardment. The rest of the colonies decide they want nothing to do with such stupidity and tell both sides to fuck off until they start acting like adults.

This would result in a Cold War-style arrangement over the next several decades, with Earth and the independent colonies trying to recruit the neutral colonies, as all three sides expand to exploit the resources of the solar system. The returning comet is destroyed/diverted, and everyone focuses on their usual petty human squabbles instead of outside threats.

This is when I wanted to have some other disaster come in and force them to get their shit together. They'd have plenty of time before things got bad, and would spend it working together trying to come up with a viable means of interstellar travel with STL technology, no cryogenic bullshit, etc.

Even if we do evac the Sol system there is no need to immedietly head to Alpha Centauri or beyond. Plenty of oort cloud bodies and rogue planets in the dark depths of interstellar space for resource and energy needs.

I kind of had an idea of a vast interstellar fleet evacuating the system when it finally became necessary (being typical humans, with the exception of a few intrepid explorers acting as scouts who left decades ahead of everyone else, we wait until the last minute to pack our stuff and get out of town). I have no idea how feasible it is (probably not very), but I figured if, in this story, O'Neill Island 3 cylinders were the most popular space-hab, maybe there would be a project to convert them into Rama-style generation ships alongside purpose-built spacecraft and at the designated time, the entire fleet would blast off into interstellar space and people would continue to live fairly normal lives for centuries as they flew about looking for a new system to call home; probably just approach the nearest system, mine it for resources, build a few new ships as populations expand, some ships would stay to permanently settle the new system, and then the fleet would move on for the next closest star.

Mainly I was inspired by Rescue Party by Arthur C. Clarke in having the big fleet of ships moving through interstellar space, but when I got stuck on finding a reason for humans to venture outward en masse, I just copped the idea of the sun exploding or something.

[Swindle1984]

I think that for ET the cheapest way would be to divert the course of some asteroids towards Earth. It won't be a disaster since we could always blow them up but I recall a recent event where an asteroid went unnoticed between Earth and the Moon. There will be limits to our capacity to protect the population.

With such thing going public, governments will start building space stations for A-defense and B- start building O'Neill like ships just in case. They will probably also pack some weapons to give ET a 'warm' welcome.

if ET uses STL travel, they will probably come at full force like ID4 and Earth would probably just have time to build only a small fleet and probably around the gas giants to be able to mine helium from them and ore from the asteroids. Their own gravity field may provide also protection from whaatver ET launches at us.

Just had an interesting thought- in my scenario, humans have become interstellar migrants, with a vast fleet of ships traveling from system to system, extracting resources (and often leaving permanent settlements) before moving on to the next system. A few ships that left decades earlier are acting as scouts, relaying information on hazards, resources, etc. to the main fleet.

What if the aliens are doing the same thing? The comet attack was launched by a scout ship that detected us on its approach; the main fleet can't divert its course from our system because it's already decelerating and needs to stop here for resources. Bypassing the system would put too much of a strain on them and threaten the fleet's existence, hence the scout decides the best option is to try killing us since we pose a potential threat to the fleet (being not too horribly far behind them technologically, and probably not fond of the idea of a bunch of aliens coming and strip-mining their system before they do.). The scout is intended to simply fly past the system before heading along ahead of the main fleet, hence why we could miss its approach and why it would only launch the one attack and then leave us alone for decades or even a century or two.

With the main fleet approaching, with the intent of setting up shop here until they had enough resources to resupply and expand their fleet and move on to the next system, we'd launch a mass exodus to flee before they tried to wipe us out. Naturally, a portion of the population would stubbornly remain behind, either to fight off the aliens or attempt to negotiate with them.

Thus, we end up doing the same thing as the aliens.

[Junghalli]

Mainly I was inspired by Rescue Party by Arthur C. Clarke in having the big fleet of ships moving through interstellar space, but when I got stuck on finding a reason for humans to venture outward en masse, I just copped the idea of the sun exploding or something.

What about having humanity threatened by aliens?

1) It's the kind of threat that would legitimately be a decent reason to evacuate the solar system (works well in an STL universe; we'd potentially have centuries if warning if their ships don't travel at a large fraction of c).

2) It'd give us a reason to avoid permanently settling down anywhere else, since if we kept moving we'd be a lot harder for the aliens to find or intercept.

3) It's more interesting than a simple natural disaster.

Basically what I see you're thinking of already.

[Solauren]

Another reason to evac Earth, if not the solar system;

SOme kind of massive environmental disaster, that causes a raise in radition levels. Something that can be treated, but re-exposure requires retreatment. Something that can be 'slowed' to prevent fatalities as well.

And something that, economically, it's not worth living on Earth anymore for anyone, so a mass evac is needed.


Or, a rogue planet on an intercept course would do the trick.

[Junghalli]

Or, a rogue planet on an intercept course would do the trick.

Trouble with that kind of thing is (as you noted) it's a good reason to evacuate Earth, but not the solar system. Catastrophes like asteroids, rogue planets, another star passing through the solar system etc., would be survivable to a habitat-based civilization. You need something seriously horrible for running to another star system to start to look like a smart idea.

[Swindle1984]

Or, a rogue planet on an intercept course would do the trick.

Trouble with that kind of thing is (as you noted) it's a good reason to evacuate Earth, but not the solar system. Catastrophes like asteroids, rogue planets, another star passing through the solar system etc., would be survivable to a habitat-based civilization. You need something seriously horrible for running to another star system to start to look like a smart idea.

An entire fleet of technologically advanced aliens who will probably be peppering all your habs and worlds with projectiles traveling at significant fractions of C would probably fit the bill.

I like the idea of one or two generation ships settling permanently in systems visited by the human fleet; some people would be sick of traveling and want a change of pace in a star system all their own. They know how to live without a planet by now, and as their population expands so would their habitats as they strip the system of its resources. The main fleet, meanwhile, will have resupplied, refueled, and finished any repairs or additions to the fleet as needed, and headed off for the next system.

It not only makes humanity that much harder to wipe out (say, if the fleet was intercepted or approached a populated system that could feasibly destroy it), but it also means that anyone following behind the fleet with sinister intentions is going to have to deal with a rearguard, which will likely send out a warning if not inflict damage.






Now, if you had a Rama-style generation ship or converted O'Neill cylinder, the cylinder rotates so centrifugal force generates "gravity". How fast could your ship accelerate without the acceleration fucking up "gravity" inside the cylinder? This is important not only for establishing what the ships can do, but also how long it would take them between systems.

[Junghalli]

Now, if you had a Rama-style generation ship or converted O'Neill cylinder, the cylinder rotates so centrifugal force generates "gravity". How fast could your ship accelerate without the acceleration fucking up "gravity" inside the cylinder? This is important not only for establishing what the ships can do, but also how long it would take them between systems.

I imagine effectively simultaneous accelerational and centrifugal gravity would probably feel somewhat like being on a slope. If your centrifugal gravity is 1 G and your accelerational gravity is .1 G you drop something and in 1 second it's fallen 10 meters toward the bottom of your ship and 1 meter to the back. On level ground (relatively to centrifugal gravity) you will always feel a force pulling you toward the back of the ship. The less the difference between centrifugal and accelerational gravity, the steeper the slope effectively becomes.

1/10 of your centrifugal gravity would probably be merely annoying for the most part. Half of it... probably isn't going to work. Mind you, you can compensate somewhat by increasing your centrifugal gravity: it doesn't have to be 1 G.

Under normal operations it would probably be best just to stick to very mild accelerations. Even .01 G will get you up to .1 c in 10 years. And it would be hard to accelerate giant habitat ships very fast anyway.

[Solauren]

Your space civilization could have been screwing around with the sun, and fucked something up so badly, the solar system isn't habitable. Say, 'oops'.

Just make what they did, and the full effects 'classified', and all done. Maybe the sun is using up hydrogen x10's faster (with a x10 increase in radiation levels).

Try to avoid the 'alien fleet pursuing them' angle. To Battlestar Galactica

[Patrick Ogaard]

How about a brown dwarf, i.e. Jupiter's big brother, that normally wanders about a comfortable distance from Sol? Some passing star a few million years ago disturbs its incredibly long orbit around Sol, or maybe an interaction with another brown dwarf.

Suddenly, we've got a slow steamroller cruising into our solar system. There's no way to stop or deflect something that big, and, one by one, the planets and asteroids of the solar system wil find themselves pitched out of their customary orbits. Whether the body goes on a slow trip into interstellar space or a faster trip into the thermonuclear furnace of the sun, it's game over for that body. Either the brown giant ends its performance by smashing into the sun, prompting deadly flares, or it goes into a uselessly close orbit around Sol. Either way, our solar system suddenly becomes a lethally empty place.

A viable option might actually be to build mobile O'Neill cylinders and similar big spacecraft, then try to hitch a ride on the gravitational coattails of a planetary body heading out into interstellar space. If Jupiter were to get bumped out of the system complete with its entourage of moons, that would probably be enough to keep a prepared near-future civilization going for a good long time, and even a fast-cooling and ruthlessly stripmined Earth could be a useful resource base and gravitational tug for a civilization that tucks itself into orbit around the planet.