Orbital Mechanics Questions

[ajanders]

I've got d20 Future, and I'd like to run a Firefly campaign in a fairly hard sci-fi style.
So I need a solar system with lots of human inhabitable planets.
It occurred to me that the best way to generate that system would be to steal from Odyssey 2010: imagine a solar system like ours, but with Jupiter turned into a sun. This makes all the Jovian moons pretty habitable, which is a good number of worlds available for terraforming and settlement.
Here's where the question comes in I don't know how to answer.
What might the day and night cycles look like for the "Jovian Moons" and "Terra"? "Mars"?
I can intuit that the night cycle will be brighter for any planet between "Sol" and "Jupiter/Lucifer". But I think...but can't prove...that almost all the planets in the system will have at least some points in their orbits where either "Sol" or "Lucifer" will be eclipsed by the other star in the system, meaning there will be no change in their day and night cycles.

Oddly enough, I think I can handwave everything else: I know there will be some changes in radiation levels and climates, due to the extra heat, but that would be one of the things that gets handled by terraforming work and technology, mostly.
But I'm reluctant to handwave days and nights.
Can anyone give me any help for how to start approaching this problem?
I should mention I'm really not that good at math, too, but I'll try not to require spoon-feeding.
Thanks for all your help.

 

[0-hr]

I think that it would be a lot like nights with a full moon (though maybe brighter depending on the distance to Lucifer and the size of the stars involved) except that the "moon" would always be full if it were anywhere in the sky.

Anyway, my point is that there are certainly times when neither the sun nor the moon are in the sky. These drift on a monthly cycle for the Earth and the Moon but would be more like a yearly cycle for the Sun and Jupiter. For much of the "year" both stars (near and far) would be near each other (from Earth's point of view) and so the day and night would be much like normal. As the months went by, they would separate in the sky. So about 6 months later, they would be opposite each other. You'd have a major day followed by a minor day with little or no true dark in between. But six months later (give or take) you'd be back to 12 hours of full day followed by 12 hours of full night.

That's my best guess anyway.

 

[Turanil]

I've got d20 Future, and I'd like to run a Firefly campaign in a fairly hard sci-fi style.
So I need a solar system with lots of human inhabitable planets.

Hard Sci-Fi? The first thing I would say, is that the odds for a solar system having lots of human inhabitable planets is probably extremely low if not impossible.

Anyway, I would suggest to search on the Internet about astronomy, or buy a book like this one.

I am not a specialist, but I would point out this: If you were to design a solar system almost identical to our own, I would nonetheless add important differences to the planets:

--Climate would be somewhat related to the distance to the sun. So the closer the hotter, the farther the colder. Maybe on a very hot planet humans could only live on the poles (that would be tropical), or with special equipment. Note that a planet far from the sun could still be hot enough provided it has a thick atmosphere (greenhouse effect), but the planet would be extremely gloomy. On a planet near the sun, humans would have to protect from the dangerous radiation from the sun.

--Are all native creatures of the different planets based on the same DNA? Are plants and animals from one planet edible for creatures from another planet? (even if based on the same DNA): I doubt it... Humans would probably have had to adapt (bringing their own sources of food).

--Gravity and atmosphere: I suggest variations, and that humans must adapt when not on their native world. Maybe they must wear masks to breath on some worlds, although the atmosphere can allow life forms.

--Jupiter should be the smallest kind of a brown dwarf, because of radiation from the star who would otherwise prevent life. Atmosphere for a livable moon probably requires to be thick to stop radiation and have some greenhouse effect to retain heat. This world would be much gloomy, with a poor light from the Jupiter/brown dwarf, and almost no light from the sun too far away. Native creatures would either have some Darkvision, or would not rely on sight sense (more of sonar like bats).

Well, I say all of this off the top of my head. My suggestion is that in doing scientific research to determine your planets, and put enough differences to them, you could come up with a really interesting system, and all the more credible.

 

[Mustrum_Ridcully]

I am not sure the idea of a second star in the solar system would be that great - it could actually screw up everything, at least if he is located at Jupiters position.

But you might consider a multiple star systems where the stars aren´t too near, but not too far either. Maybe a star at the distance of Pluto.
It would take a lot of travel time between the different planets, but not require FTL engines ...

Earthlike life is possible in certain areas around a star - to near, it gets to hot, to far, it gets to cold.
If you make a twin star system, you might be able to have three habitable zones - one directly around each star, a third one midway between the two.
Still, you must find a way to ensure that a planet stats in the midway one without losing his orbit. Maybe he is in the gravity centre (or is it LaGrange point?) between the two stars (and thus doesn`t need to move relatively to them), or it is a moon of a gas giant that anchors him in the middle.

It might also help if you use "double planets" (planets of similar mass at similar positions - make the earth´s moon a bit heavier, and the earth a bit lighter) to get more planets per region.

It would still raise the question how such a star system could be naturally created, but considering the big space of the universe, it might be a possible result and thus exists, and the question is only as unanswerable as the general question for the life, universe and the rest.

 

[Pbartender]

A better idea, than turning Jupiter (or any gas-giant) into a star, would be to put the gas giants into the habitable range of the star.

For example, build a star system with a Jupiter-like planet at Earth's orbit, a Saturn-like planet just inside Mars' orbit, and a Uranus-like planet just outside Venus' orbit.

Each gas giant would have scads of moons, a handful of which could be earth-like, and dozens upon dozens that could be colonized using space-technologies.

You could even give one of the gas giants a habitable atmoshperic layer... At a certain altitude from even a gas giant, gravity would be about earth-equivalent. Assuming an breathable oxygen-nitrogen layer at that altitude and the proper weather to keep a temperate climate (you would necessarily need to be close to a sun, though it would help), it could be inhabited, so long as you have the technology to keep your cities suspended in the air (ala Star Wars' Cloud City on Bespin).

It's a little fantastic, but can have enough grounding in (pseudo-)science to qualify as the harder sort of sci-fi.

Not to mention... That real-life astromoners have discovered a significant number of planets oribiting other stars that fit this sort of description exactly. We don't know what their satellites look like, but there are quite a few gas giants orbiting within the 'goldilocks' regions of other stars.

 

[ajanders]

I think that it would be a lot like nights with a full moon (though maybe brighter depending on the distance to Lucifer and the size of the stars involved) except that the "moon" would always be full if it were anywhere in the sky.

(deletia...)

You'd have a major day followed by a minor day with little or no true dark in between. But six months later (give or take) you'd be back to 12 hours of full day followed by 12 hours of full night.

I think it's a little more light than that. Assuming "Lucifer" generates as much light as "Sol", it's four times as far away from the "Earth" as "Sol" is. So it should be only 25% as bright. Visualizing that is a little difficult for me, but I think it's brighter than a full moon.
Of course, the assumption that "Lucifer is as bright as Sol" is a pretty big assumption. If that's not right, you may be right after all.
I'm mostly hoping for the periods here, but I'll have to check to see how the light changes as well, as it may just let me close the question.

 

[ajanders]

Hard Sci-Fi? The first thing I would say, is that the odds for a solar system having lots of human inhabitable planets is probably extremely low if not impossible.

Well, most of them would have been "fixer-uppers"...I think historically there must have been a lot of terraforming work done and done well enough that people can stop thinking about survival and start thinking about politics and commerce. I still have to figure out what that terraforming would have been, mind, but I have some ideas that can be enough unless someone wants to play a planetary ecologist.

Anyway, I would suggest to search on the Internet about astronomy, or buy a book like this one.

Internet searches I have done, but I didn't know about this book. *Sigh*...yet another delay in getting the Iron Kingdoms Players Guide .
Thanks.

I am not a specialist, but I would point out this: If you were to design a solar system almost identical to our own, I would nonetheless add important differences to the planets:

Good points, all.
It has occurred to me this may not be doable in a very hard science way, but it'll be worth some experimenting.
(Or I could just cheat and grab a good star system from Traveller.)
The credibility issue doesn't have to be perfect: I'm not playing with a bunch of physicists or astronomers and I don't think I'm going to wind up having a bunch of characters doing planetary surveys. I just wanted to follow the concepts as far as I could get them to go and see if anything interesting popped out.

 

[ajanders]

I am not sure the idea of a second star in the solar system would be that great - it could actually screw up everything, at least if he is located at Jupiters position.

My understanding is that it depends on the mass of the star: if the star has the same mass as Jupiter, nothing changes gravitationally.

It would still raise the question how such a star system could be naturally created...

Well, some of it's not natural: there's probably been at least a century of PL 6 or 7 terraforming intervention on these planets: which could do quite a bit of work.
As for the other sun...shh! You're coming close to a Campaign Secret (tm)

 

[bubbalin]

(deletia...)

I think it's a little more light than that. Assuming "Lucifer" generates as much light as "Sol", it's four times as far away from the "Earth" as "Sol" is. So it should be only 25% as bright. Visualizing that is a little difficult for me, but I think it's brighter than a full moon.
Of course, the assumption that "Lucifer is as bright as Sol" is a pretty big assumption. If that's not right, you may be right after all.
I'm mostly hoping for the periods here, but I'll have to check to see how the light changes as well, as it may just let me close the question.

Just a correction.
But I believe light like most energy has an inverse square relationship. Thus four times the distance means one sixteenth of the light.
Though of course, I'm not sure how light is measured, whether it is a linear type of scale or log scale like decibels...
Okay, lots of tangents here...

Another thing with habitable planets is that they are in what is called a 'goldilocks' orbit. That is, not too hot, not too cold...

I assume you don't have a binary star system (Like Tattooine) though right? More like Yavin with a series of planets orbiting a gas giant. (Sorry, my Red dwarf knowledge is negligable, but star wars I can handle...)

 

[Mustrum_Ridcully]

My understanding is that it depends on the mass of the star: if the star has the same mass as Jupiter, nothing changes gravitationally.

I am not sure if a star of the mass of Jupiter can maintain the fusion process neccessary for a "real" sun. (And it would probably be artificially or "accidently" initiated)
But my main problem is the additional source of heat/radiation/light. I am not sure if it wouldn´t screw with the ecosystem of a planet.
(I think the scenario of 2010 would be fatal for humanity and most earth life - If the ecosystem of the planet was created with the two suns, this doesn`t apply...)