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Greetings,I'm currently working on a fantasy series that takes place on a planet far, far away (yeah, I know), and I'm looking for some expert advice. I'd like for the planet to exist in a binary star system and have multiple moons (one of the plot points involves highly unpredictable and unstable seas and tides). I fully admit I'm not much of a scientist, though I do have an amateur's interest in quantum mechanics and basic physics and math.In any event, my primary goal is to get the science right. Sure, I could make up an alternate universe where our rules of physics don't apply, but that seems like it would be even more complicated.Anyway, I look forward to interacting with many of you and hope that some of you can help me make my world credible.
Keep in mind that we define days and years based on the spin and orbital period of Earth. If another planet had a slower spin or longer orbital period, then they would probably define time differently from us.In our solar system, Jupiter has an orbital period of just under 12 years. So, depending on the planetary tilt and eccentricity of the orbit, a planet (or moon) in Jupiter's orbit might have a 6 year summer, and a 6 year winter.It would be mighty cold that far from the sun, unless one had a sun that was much hotter than our own.Keep in mind that we also have multi-year weather patterns on Earth including El Niņo, La Niņa, NAO, PDO, AMO, etc without necessarily all the fancy orbital characteristics.
Sounds like a nifty idea! I am an amateur astronomy enthusiast, but by no means an expert, so perhaps I can be of limited help.There are many types of binary star systems. To get a planet in a stable orbit you probably want to have the stars fairly close together compared to how far the planet is from each of them (case A in attachment--NOTE: these are not drawn to scale!). It may also work if one star is very massive and the other star is significantly less massive (least massive stars are red dwarfs http://en.wikipedia.org/wiki/Red_dwarf, which are still about 7.5% as massive as our sun), with an orbit much farther out than the plant's orbit (case B). You may even be able to work out a solution for a planet orbiting a small star, which itself orbits the larger star (case C; imagine if Jupiter were large enough to be a red dwarf, then one of its outer moons could be said planet)--I don't know how likely it would be to have a moon orbiting a planet orbiting a star orbiting a star though...If you opt for the planet orbiting both stars (case A; circumbinary orbit) note that the habitable zone around the stars may be much further out than our is: it might not be unreasonable to have an orbit that take 7 of our years... The closer the stars are to each other the faster they will appear to move around each other in the sky of said planet. This will probably have the least variation in the amount of light reaching the planet. Case C would probably have the greatest variation. My guess is the least variation would still be enough to make things interesting without making the planet inhospitable...These three cases are extremes for which the calculations are easiest, and stable solutions are more likely to be found--of course there are many different ways that the three bodies could orbit one another...Just for kicks: there is also known system that has four suns and a planet with a (somewhat) stable orbit! (http://www.bbc.com/news/science-environment-19950923 and http://arxiv.org/abs/1210.3612)
One idea I've been kicking around is having long periods (say, 7 year intervals) of relatively mild weather, mostly warm and rather tropical followed by the same length interval of relatively harsh weather, cold with a good deal of precipitation...
I'm trying to imagine what it would be like to replace Jupiter with a Red Dwarf sun. It may actually be relatively stable. Perhaps push it a little further out?Once a year, it would be lined up behind the sun, and would be about 43+8 = 52 light minutes away.Once a year it would be on opposite sides of the earth from the sun, and 43-8 = 35 light minutes away. Other times of the year, it would be at other angles. I'm seeing notes that the minimum brightness would be about 0.00125% that of the sun (and 4 to 6 times the distance). It might toss the tides around a bit, especially during those times when the Sun, Earth, Moon, and Jupiter (red dwarf) were aligned.No doubt the extra star would throw the seasons out of kilter on a 12 year (6+6) orbit, especially during those times when it was opposite Earth (closest pass) during either the summer or winter which might lead to a warmer than normal summer/winter (even just a degree or two might make a difference) which would be followed by the opposite season 6 months later (when it was at the furthest part of the orbit) and a cooler than normal winter/summer.When hitting in the spring, it might be a warm spring, and hitting in the fall, a lengthened growing season.
Quote from: mjtobias on 07/01/2015 14:15:33One idea I've been kicking around is having long periods (say, 7 year intervals) of relatively mild weather, mostly warm and rather tropical followed by the same length interval of relatively harsh weather, cold with a good deal of precipitation...Check out the Helliconia trilogy by Brian Aldiss. Here's a couple of bits from the reviews:"The planet Helliconia orbits the sun-like star Batalix every 480 days (a "small year"). Batalix in turn orbits a white supergiant star, Freyr, once every 2498 Earth years (1825 Helliconian small years). During this time, Helliconia undergoes climate changes ranging from Arctic to Saharan..."
... I'd like for the planet to exist in a binary star system ...
Quote from: mjtobias on 06/01/2015 18:12:03... I'd like for the planet to exist in a binary star system ...http://en.wikipedia.org/wiki/Three-body_problemThe results of the three-body-problem can be chaotic ... http://vimeo.com/11993047#t=25s
I just came across a simple toy solar system builder you might be interested in playing with:http://apod.nasa.gov/apod/ap150112.htmlthere are probably better ones out there, but this one entertained me for a good 20 minutes...
If I were to create my world with this scenario, where Jupiter is the red dwarf and once a year it is on the opposite side of the earth away from the sun, would that result in 24 hours of sunlight for the citizens of earth? Or would it be more like day and dusk rather than day and night?
The trick in your fictional system would be to get the size of the dwarf star just right so that the luminous effects would be significant, but the gravitational effects would be bearable.