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Any chance someone could make a diagram of the orbit for us? I really can't picture this? Does it make a figure 8 around the first two stars?

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InclinedPlane 14y ago
It's a pair of binary stars with a planet orbiting one pair. To give you a conceptional model, imagine that Mercury is a star and then imagine that, say, Saturn and one of its moons are also stars. Now, obviously, orbital mechanics are going to change when you have all of these much more massive bodies in the system, but hopefully you get the picture. Edit: obviously not to scale, but maybe this helps: http://i.imgur.com/RJrOw.png http://i.imgur.com/RJrOw.png
- jmilloy 14y ago
  Your parent is asking how the planet orbits two stars, and probably how the 2-star-1-planet system orbits the two other stars. That is, "how does any body orbit two stars?"
  - InclinedPlane 14y ago
    And I explained. How does the Earth orbit the Sun-Mercury system? It's no different than how a planet orbits a binary system from afar. The two stars orbit each other and then the planet orbits around both stars. And then that whole system orbits around another binary star system at a tremendous distance (1,000 AU, ten times farther away than Voyager 2 is from the Earth now).
    - fusiongyro 14y ago
      It's a little different; in our solar system, the Sun is one of the foci of the ellipse, whereas in a binary system that focus would instead be the center of gravity between the two stars.
      - InclinedPlane 14y ago
        Yes, though in this case the big star weighs nearly 4x as much as the little star, so it's a matter of one star shuffling around in a small ellipse with the smaller star in orbit, rather than a more intimate orbital dance if the stars had been closer in mass.
      - drcube 14y ago
        Although Mercury in this instance is extremely insignificant, technically the earth orbits the center of gravity of the Sun and Mercury. Actually, the center of gravity of the Solar system as a whole, but I'm just going along with the GP.
        fusiongyro 14y ago
        Gosh, how incredibly helpful.
      - jobigoud 14y ago
        We still have an analogy in the Solar system, Hydra and Nix orbit the Pluto-Charon binary. The barycenter of the Pluto system is outside the surface of the dwarf planet. http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Pluto_and_its_satellites_%282005%29.jpg/250px-Pluto_and_its_satellites_%282005%29.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Plu...
  - TeMPOraL 14y ago
    Normally, it doesn't orbit two stars, it orbits their combined center of gravity (which, if the stars were the same mass, would lie exactly between them). Or to be more precise, both the stars and the planet together orbit their combined center of mass.
  - JoeAltmaier 14y ago
    Its complicated. You can approximate it using the 2-star-center-of-mass, but thats skipping over important stuff. See, the stars are orbiting one another. At any time one may be closer/further away than the other from the planet. That makes the COG appear to 'wobble'. IF the planet is in something like a 'lagrange point' where it always sees both stars in the same relative position, then the COG approximation is true. Otherwise the planet will behave in a more complicated manner, and in fact may not have a stable orbit at all.
- tocomment 14y ago
  Thanks. That is helpful. So there's no scenario where a planet could be in a figure 8 orbit? That would be amazing.
jmilloy 14y ago
It's probably similar to other two-sun planets. The planet orbits around both stars at the same time, which are close together. http://galileospendulum.org/2011/09/15/a-planet-with-two-suns/ http://galileospendulum.org/2011/09/15/a-planet-with-two-sun...
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SoftwareMaven 14y ago
The point the earth actually orbits around isn't actually in the middle of the sun. It is at the center of mass between us and the sun. A planet orbiting a dual star system will do the same thing, but the center of mass winds up being somewhere between the two stars.

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InclinedPlane 14y ago

It's a pair of binary stars with a planet orbiting one pair. To give you a conceptional model, imagine that Mercury is a star and then imagine that, say, Saturn and one of its moons are also stars. Now, obviously, orbital mechanics are going to change when you have all of these much more massive bodies in the system, but hopefully you get the picture. Edit: obviously not to scale, but maybe this helps: http://i.imgur.com/RJrOw.png http://i.imgur.com/RJrOw.png

jmilloy 14y ago
Your parent is asking how the planet orbits two stars, and probably how the 2-star-1-planet system orbits the two other stars. That is, "how does any body orbit two stars?"
- InclinedPlane 14y ago
  And I explained. How does the Earth orbit the Sun-Mercury system? It's no different than how a planet orbits a binary system from afar. The two stars orbit each other and then the planet orbits around both stars. And then that whole system orbits around another binary star system at a tremendous distance (1,000 AU, ten times farther away than Voyager 2 is from the Earth now).
  - fusiongyro 14y ago
    It's a little different; in our solar system, the Sun is one of the foci of the ellipse, whereas in a binary system that focus would instead be the center of gravity between the two stars.
    - InclinedPlane 14y ago
      Yes, though in this case the big star weighs nearly 4x as much as the little star, so it's a matter of one star shuffling around in a small ellipse with the smaller star in orbit, rather than a more intimate orbital dance if the stars had been closer in mass.
    - drcube 14y ago
      Although Mercury in this instance is extremely insignificant, technically the earth orbits the center of gravity of the Sun and Mercury. Actually, the center of gravity of the Solar system as a whole, but I'm just going along with the GP.
      - fusiongyro 14y ago
        Gosh, how incredibly helpful.
    - jobigoud 14y ago
      We still have an analogy in the Solar system, Hydra and Nix orbit the Pluto-Charon binary. The barycenter of the Pluto system is outside the surface of the dwarf planet. http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Pluto_and_its_satellites_%282005%29.jpg/250px-Pluto_and_its_satellites_%282005%29.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Plu...
- TeMPOraL 14y ago
  Normally, it doesn't orbit two stars, it orbits their combined center of gravity (which, if the stars were the same mass, would lie exactly between them). Or to be more precise, both the stars and the planet together orbit their combined center of mass.
- JoeAltmaier 14y ago
  Its complicated. You can approximate it using the 2-star-center-of-mass, but thats skipping over important stuff. See, the stars are orbiting one another. At any time one may be closer/further away than the other from the planet. That makes the COG appear to 'wobble'. IF the planet is in something like a 'lagrange point' where it always sees both stars in the same relative position, then the COG approximation is true. Otherwise the planet will behave in a more complicated manner, and in fact may not have a stable orbit at all.
tocomment 14y ago
Thanks. That is helpful. So there's no scenario where a planet could be in a figure 8 orbit? That would be amazing.

jmilloy 14y ago

It's probably similar to other two-sun planets. The planet orbits around both stars at the same time, which are close together. http://galileospendulum.org/2011/09/15/a-planet-with-two-suns/ http://galileospendulum.org/2011/09/15/a-planet-with-two-sun...

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SoftwareMaven 14y ago

The point the earth actually orbits around isn't actually in the middle of the sun. It is at the center of mass between us and the sun. A planet orbiting a dual star system will do the same thing, but the center of mass winds up being somewhere between the two stars.