Assistance needed with sci fi novel

[steve77]

Hi all,

Thank you for the pleasure of being part of this forum. I'm sorry if this is in the wrong area, please feel free to move this post if it is.

I'm in the process of creating a science fiction novel and I need some help please.

Very simply, Earth has over time destroyed itself and a group of people are chosen to relocate to a new solar system.

I need to have a system that contains 4-6 planets/moons that are habitable for humans to live on.
I know its not possible for this to work with a single star solar system, so my thoughts have moved to a binary system. (Please correct me if this is not possible)

I would like to also have non habitable planets also to add to the realism of the solar system.

The planets/ moons need to be able to support life much the same way as on Earth. I am open to subtle differences though. These planets will not contain any aliens (little grey men), however they can contain alien plant life, native to the planets.

I want this to be as scientifically correct as possible. I do realize that there will probably be some sort of 'bending of the rules' needed.
I'm happy to take as much advise as you're willing to give in order to make this work.

Please can i have only people who know what their talking about. I don't mean to be rude but I've had a lot of people waste my time with this.

Those who are directly involved in assisting with this project shall have their names (if desired) included in my 'Thanks' section.

Thank you for your time to read this.

 

[Jilang]

Hi Steve, what about a former asteroid belt that has since coalesced into several sizeable planets all at the same distance from the star? Would that work?

 

[steve77]

Hi Jilang,

Thank you for your reply.
As long as this would work for the amount of planets i need. Would this be possible in a binary system? Fitting that amount of planets into the goldilocks zone around one star seems a bit far fetched.
Im not going to go into too much detail as to how the solar system was formed. I do however wish it to be able to operate as needed for the story.

 

[Jilang]

I don't see why not. Binary systems may actually be more conducive to Goldilocks planets due to better atmosphere retention in their early years, see this article.
http://www.astrobio.net/pressrelease/5570/two-suns-better-for-life

 

[Bandersnatch]

Hi Steve, what about a former asteroid belt that has since coalesced into several sizeable planets all at the same distance from the star? Would that work?

Would not. Such a situation is unstable, and the planets would not stay all in the same orbit.

The simplest solution would be to have a large gas giant, up to a brown dwarf, with a number of moons. The giant would lie in the habitable zone of the star it's orbiting, and so would all of its moons.

There's a number of threads in the Science Fiction Writing subforum with similar questions. A forum search should net some useful results.

 

[Jilang]

Would not. Such a situation is unstable, and the planets would not stay all in the same orbit.

That's interesting. Why would that be the case? Is our asteroid belt unstable too? I like the idea of a gas giant, but wouldn't there be huge tidal forces?

 

[steve77]

Is there some way I can make an online working model of this? I don't want to just say there's a gas giant without knowing its size and how far from the sun/ suns it is. I do like the idea of two suns, which means I can have at least a couple of planets and the rest moons.

I just want this to be as scientifically correct as possible.

Thanks for your help.

 

[Bandersnatch]

@steve77: have a look here:
https://www.physicsforums.com/showthread.php?t=705029
there's a discussion and some links to habitable zone calculators to help you place the planet(s) at correct distances.
The gas giant may be anything from Neptune's to 10-ish Jupiter masses large. Larger one would make more sense if there are to be large moons around it.
Let us know what you come up with, and we'll review it.

That's interesting. Why would that be the case? Is our asteroid belt unstable too? I like the idea of a gas giant, but wouldn't there be huge tidal forces?

Because all masses attract, and for a body to stay in a particular circular orbit(a simplified case), there has to be no other forces acting on it but the central force of correct magnitude.
With one planet, that's just gravity. If you have a small object interacting with two massive ones, you can have certain points in the orbit around one of them, where adding all the gravitational interactions still produces a central force(http://en.wikipedia.org/wiki/Lagrangian_point), even though most of these are vulnerable to the slightest of perturbations stability-wise.
Any more bodies than that will not have a stable configuration, and any the long-term stability of their orbits must rely on large distances and orbital resonances.

As for the asteroid belt, it's a very diffuse bit of debris(you wouldn't even assemble our Moon from it) left after eons of perturbations by the nearby Jupiter(cf. Kirkwood gaps) and within itself. What's still there, happened to fall into the less gravitationally dangerous areas, and there are no large bodies there any more to perturb the belt.

The tidal forces, sure they'd be large. But it only means the moons would probably end up tidally locked, which would actually eliminate the ocean tides. There still could be tides due to orbital eccentricity shifting due to other large moons' interactions(as with the Gallilean moons of Jupiter), but it could be handwaved into something irrelevant, or interesting(volcanic worlds!).

 

[Jilang]

Because all masses attract, and for a body to stay in a particular circular orbit(a simplified case), there has to be no other forces acting on it but the central force of correct magnitude.
With one planet, that's just gravity. If you have a small object interacting with two massive ones, you can have certain points in the orbit around one of them, where adding all the gravitational interactions still produces a central force(http://en.wikipedia.org/wiki/Lagrangian_point), even though most of these are vulnerable to the slightest of perturbations stability-wise.
Any more bodies than that will not have a stable configuration, and any the long-term stability of their orbits must rely on large distances and orbital resonances.

I think I see what you are saying, but wouldn't that apply equally to the moons of a gas giant?
Similarly Venus and Mars come pretty close to the Earth at times. Perhaps no orbit is truly stable?

 

[Jilang]

The tidal forces, sure they'd be large. But it only means the moons would probably end up tidally locked, which would actually eliminate the ocean tides. There still could be tides due to orbital eccentricity shifting due to other large moons' interactions(as with the Gallilean moons of Jupiter), but it could be handwaved into something irrelevant, or interesting(volcanic worlds!).

That's got to be useful information then, the moons will probably have always the same side facing the planet?

 

[Jilang]

On the assumption that our moon is probably a captured planet would it be possible for several planets to capture each other and rotate around their common centre of gravity?

 

[tfr000]

You might want to look at this, and its home pages:
http://chemistry.unina.it/~alvitagl/solex/hiltro.gif
This is a simulation of the Trojan asteroids of our Solar System, objects which actually exist. Probably no reason why some real planets could not be in the same type of orbits.
Trojan asteroids are parked, for lack of a better word, in the Lagrangian points of Jupiter's orbit. Although, as you can see from the simulation, they circulate around the points.

 

[Drakkith]

On the assumption that our moon is probably a captured planet would it be possible for several planets to capture each other and rotate around their common centre of gravity?

Our moon is most likely a result of a large impact with Earth knocking off a portion of the crust. But to answer your question, it's extremely unlikely, as a triple body system is very very unstable in this situation. Their orbits would get very chaotic and unpredictable, and it is possible (or probable) for one or more of the planets to be ejected from the others into a much different orbit around the star.

 

[Decimator]

One question you'll want to answer is why they chose to head to a new system instead of spreading throughout our system. Are these guys a splinter faction, a colonist fleet, or something else? How far away is the target system? What's the tech level? You can do interstellar with a high-end Orion, but it'll be slow.

 

[DHF]

Decimator has a good point. If the characters are at a technological level where they can travel travel to and colonize another system then its very easy to believe that they have more then enough technology to colonize several bodies in our own system. Technologically we are almost at the point where we can colonize Mars. It would take a staggering amount of resources shipped there but in theory its possible. and that is with current tech. Safely landing a manned crew is still a bit touchy but we are only a few years away from having that solved. As it has been discussed and calculated in other threads, accelerating a ship to even a fraction of the speed of light takes a truly sickening amount of energy. If your characters have that much power at their disposal then setting up shop on Mars or Europa or Titan would be far easier then traveling for years to reach another star.