A planet question.

Jean · Mar 14, 2012

Hello everyone, I'm working on a concept for adventure story, but firstly, let me show you.

That's the planet in the question. Yes, it's inspired by Kepler-16b, the real life "Tatooine". Ruu orbits two host stars Paika and Miami (pronounce miæmaɪˈ, reverse of Florida's Miami) but I'm not curtain how's that gonna effect Ruu's weather.

I think that when Ruu orbit closer to Paika, it'd get more energy than when it's closer to Miami; then, Ruu will have several summers a year, am I right? And as Paika and Miami eclipse each other, there will be dim times in a sky of Ruu, am I correct? Then another question, during the eclipse period the temperature would be colder on Ruu right?

Drachen Jager · Mar 14, 2012

IMO the orbit of Paika is too eccentric. Miami looks too small to have such a large pull.

You are going to have an odd summer/winter cycle for sure. To know the pattern of winter/summer cycles have a look at an orbital simulator. http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html (there are others too, if you don't like that one)

I would say the Maimi summer would be much weaker than the Paika summer, but AFAIK that has to do with size and type. If they're both similar types I'd expect winter/summer to be about half to a quarter as strong on the Maimi cycle.

Keep in mind that on Earth one of the biggest seasonal modifiers is the axial tilt, not our proximity to the Sun. How ovoid/circular the path of Ruu is would change things too. Certainly Miami would have some impact on Ruu's orbit, which would give it a very eccentric cycle (not really circular or ovoid).

Jean · Mar 14, 2012

IMO the orbit of Paika is too eccentric. Miami looks too small to have such a large pull.

That chart isn't scale (I have no ability to measure it precisely

). To make things simple I think of Paika as 0.8 solar mass while Miami is 0.4.

You are going to have an odd summer/winter cycle for sure. To know the pattern of winter/summer cycles have a look at an orbital simulator. http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html (there are others too, if you don't like that one)

Ahh, thank a lot.

Keep in mind that on Earth one of the biggest seasonal modifiers is the axial tilt, not our proximity to the Sun.[/qoute]

I'm thinking of that too, so, I make Ruu axial tilt very small, just few degree.

[qoute]How ovoid/circular the path of Ruu is would change things too.Certainly Miami would have some impact on Ruu's orbit, which would give it a very eccentric cycle (not really circular or ovoid).

Kepler-16b orbits very circular despise orbiting two stars.

Drachen Jager · Mar 14, 2012

Hmm, but Kepler 16's two stars have a larger difference in size than your model. The primary is .68 solar masses and the secondary is .2. Your larger size differential would make the orbit more eccentric (though I really can't guess by how much).

Kepler 16b is also on the cold side of habitability (-60 to -100 Celsius). If you want it to be more Earth-like it has to be closer, and closer would mean more eccentric again.

In the end though, most of your readers will not know their orbital mechanics terribly well, you can get away with some exaggeration or straight out lying on these things. I don't think it's a terribly realistic scenario because the orbit will be inherently unstable, which is probably the reason there's only been one such solar system identified, but at the same time it wouldn't bother me much if I were to read it in a book.

Jean · Mar 14, 2012

Drachen Jager said:
Hmm, but Kepler 16's two stars have a larger difference in size than your model. The primary is .68 solar masses and the secondary is .2. Your larger size differential would make the orbit more eccentric (though I really can't guess by how much).

Kepler 16b is also on the cold side of habitability (-60 to -100 Celsius). If you want it to be more Earth-like it has to be closer, and closer would mean more eccentric again.

That's because I'm suck at math. I have no idea what proportion should stars and planet be to achieve that orbit. But let say it did, Paika-Miami system is quite circular with Ruu in habitable zone. Then I have to think about the impact of two stars to Ruu weather. Umm...

Drachen Jager · Mar 14, 2012

That's no beginner's math. I'm really good at math and I have no clue when it comes to orbital mechanics on that magnitude.

But like I say, unless you have astrophysicists reading your work you're likely in the clear. The complexity of it will keep 99.999% of your audience members from groaning and saying, "It doesn't work that way!"

Those that do say that are hopeless nerds who will pick you apart on the flimsiest grounds anyhow, so why worry about it too much? Make it within the realm of believability and forget about 100% scientific accuracy. Most SF does that to some degree or another anyhow.

Jean · Mar 14, 2012

You're right. And actually the exact number of orbit isn't importance to my story at all since Ruu's habitat is primitive human who already lost count of the fact that they'd travel to Ruu from Earth. But certainly orbit's effect on season is importance so I have to research.

thothguard51 · Mar 14, 2012

orbits are also going to effect the story in what they consider a year. It's been a while since I read about this discovery, but as I remember, the orbit is way shorter than an earth orbit. This is going to be important for not only planting of crops, but when your people start talking about how old they are...

Drachen Jager · Mar 14, 2012

Jean said:
You're right. And actually the exact number of orbit isn't importance to my story at all since Ruu's habitat is primitive human who already lost count of the fact that they'd travel to Ruu from Earth. But certainly orbit's effect on season is importance so I have to research.

Yeah, but the exact seasonal configuration is going to depend on the orbital configuration, axial tilt and rotation of Ruu.

The axial tilt you can control, so if you want stronger seasons, give it a bigger tilt. Likewise, if you want stronger seasons give it a more elliptical orbit. Both of those will produce seasons irrespective of the relative positions of the suns.

If you want the suns to have more influence, then just make it work that way. No reasonable person is going to question you on these things. Pick the seasonal configuration that works best for the story.

rachelmachelsmachel · Mar 14, 2012

Hi

As Drachen Jager said, axial tilt is more important than proximity to the sun. Much, much more important, especially when you're not talking about how elliptical the orbit is but which star it's closer to. So basically choose your axial tilt and orbital period and you've got your season length and intensity.

As far as eclipses, I don't think they'd be like eclipses here, since you're blocking out the light from one star with another star, which is also giving off light. So if Miami eclipsed Paika, you'd go from getting the light from both stars to the equivalent of just Paika, so it would go from really bright to around normal.

How long does the eclipse period last? Unless it's really long I'm pretty sure the slight decrease in solar radiation wouldn't have a noticeable effect on global climate/weather.

Also don't worry about the distance between the two stars - I've learned a bunch of spherical harmonics stuff and don't have the slightest idea.

Jean · Mar 14, 2012

As Drachen Jager said, axial tilt is more important than proximity to the sun. Much, much more important, especially when you're not talking about how elliptical the orbit is but which star it's closer to. So basically choose your axial tilt and orbital period and you've got your season length and intensity.

Thank.

How long does the eclipse period last? Unless it's really long I'm pretty sure the slight decrease in solar radiation wouldn't have a noticeable effect on global climate/weather

I'm not sure, after some simulation I found that Ruu made 3 orbits per Paika and Miami's 16 orbits (and that simulation isn't accurate too). To simplify thing I think I'll make Paika-Miami orbital period 60 days, that make Ruu's year around 320 days.

A little bit of observation and calculation will verify eclipsing period, though it's not easy. (why science and mathematics is so hard!)

Mark G · Mar 15, 2012

As I understand it, binary stars orbit around their center of mass, with an equal period, which in many cases might be measured in centuries. I would think that in an annual orbit, the twin suns would therefore remain virtually static while the planet moved around the pair.

Wikipedia article: http://en.wikipedia.org/wiki/Binary_star

Has a great animation of what it might be like on a nearby planet, watching the suns change over the course of a year:

I can imagine that a planetary orbit around them would be wobbly.

Math galore on the topic: http://www.egglescliffe.org.uk/physics/gravitation/binary/binary.html

A planet question.

Jean

New kid, but beat me hard

Drachen Jager

Professor of applied misanthropy

Jean

New kid, but beat me hard

Drachen Jager

Professor of applied misanthropy

Jean

New kid, but beat me hard

Drachen Jager

Professor of applied misanthropy

Jean

New kid, but beat me hard

thothguard51

A Gentleman of a refined age...

Drachen Jager

Professor of applied misanthropy

rachelmachelsmachel

rachelsmachel

Jean

New kid, but beat me hard

Mark G

Author of Reborn to Bite