I can think of three: planet orbits star A, planet orbits star B, or planet is WAY far away and orbits the center of mass of both stars. But are any other, more complex, orbits possible, even in theory?
Consider that the Sun is actually orbiting the center of the galaxy, and as such, is a binary system, and our planet is in orbit around it.
December 29th, 2009 at 6:50 am
I could think of a figure eight orbit, but it’d be one hell of a ride and probably not sustainable.
maybe one where the planet sits in between the two stars and is tidally locked with both of them.
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December 29th, 2009 at 7:17 am
The long term orbits of a three body system are impossible to predict. The orbits of a binary star system with one planet would be impossible to predict in the long term. The more bodies in orbit make it even more chaotic.
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December 29th, 2009 at 7:34 am
The minimum distance between the two stars where a planet can orbit either star is 100AU. That is, the theoretical planet would most likely orbit just one of the stars and never in a figure 8 pattern. I’ve got a fresh news for you to read:
http://www.universetoday.com/2009/12/10/forming-planets-around-binary-stars/#more-47329
Clear skies!
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December 29th, 2009 at 7:53 am
For the planet to maintain any sort of "stable" orbit around just one of those stars, one of a few things has to be present, the more of them, the better…
1. the planet must be at all times much closer to one of the two stars,
2. the two stars have an enormous difference in mass, and the planet orbits the more massive one, the difference in mass is great enough for the second star to only cause minor perturbations of theplanets orbit
3. the two stars must have a great distance between them,
a planet orbiting the common barycentre of the two stars seems more likely and definitely more stable in the long term. i suspect any planets orbiting just one of the two stars, especially if is was one of lesser or near equal mass of the other one, or occasionally passed close tot he one it didn;t orbit, would get pertrubed gravitationally enough to either fall into one of the two stars, or get "catapulted" out of the system all together.
i can imagine one other scenario, but the conditions are so specific, that i doubt that such a system could ever be discovered.
the two stars are the lowest mass brown dwarfs possible, and the planet is the highest mass gas giant possible. all three, being close enough in mass, could, in the short term, all orbit a single common barycenter.
i’ll see if i can find some good animated links of some similar orbits. i know i’ve seen them before, they were for complex planet/moon systems, but could apply in some cases with stars as well…
i found this instead. it assumes all objects are star sized, and given the near zero eccentricities of all the orbits, imples nearly equal mass and impossibly perfect conditions. if the planet were massive enough and the stars were small enough, some of these could be possible, but degrade over the long term.
http://www.atlasoftheuniverse.com/orbits.html
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December 29th, 2009 at 8:25 am
Consider that the Sun is actually orbiting the center of the galaxy, and as such, is a binary system, and our planet is in orbit around it.
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