# planetary orbits

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#### kratos_GOW

##### Guest
Does anyone know how close two earth size planets can orbit each other safetly. To further clairify if mars or venus were equal to the size of earth how close could they get to earth on their seperate orbit and not risk collision.

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#### MeteorWayne

##### Guest
It depends on a lot of variables, so there's no good "one size fits all" answer.
And just to be clear, did you mean two planets orbiting each other, or two planets orbiting a star in similar orbits?

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#### bdewoody

##### Guest
Venus is almost as large as the earth. I think the relevant question here is how close can the orbits of two planets approximately the size of earth orbiting a star be, without adversely affecting each other at their closest approach. And I don't know the answer to that question.

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#### MeteorWayne

##### Guest
At this point, we don't even know what the question is...

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#### kratos_GOW

##### Guest
bdewoody":14y5ifv4 said:
Venus is almost as large as the earth. I think the relevant question here is how close can the orbits of two planets approximately the size of earth orbiting a star be, without adversely affecting each other at their closest approach. And I don't know the answer to that question.
This is exactly what i was wondering. This question arose when I was reading about finding exoplanets in the habitable zone which got me wondering if more than one planet could reside within that zone. Sorry for any confusions I'm new to the wonderful world of astronomy.

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#### MeteorWayne

##### Guest

"And just to be clear, did you mean two planets orbiting each other, or two planets orbiting a star in similar orbits?"

thanx, Wayne

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#### bdewoody

##### Guest
Well my question is. How close can the orbit of two planets orbiting the sun be before they would have a disturbing effect on each others trajectory. I'm guessing that two such planets wouldn't come close very often as their orbital speed would be very nearly the same. Said planets in this case being close to earths mass.

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#### AlnitakAlnilamMintaka

##### Guest
bdewoody":2kimu0r4 said:
Well my question is. How close can the orbit of two planets orbiting the sun be before they would have a disturbing effect on each others trajectory. I'm guessing that two such planets wouldn't come close very often as their orbital speed would be very nearly the same. Said planets in this case being close to earths mass.
So technically, how close can they get as in, aphelion, perihelion? I think I get what you are saying. I'm not sure, there's probably a huge calculation in that. You might want to try some astronomical gravity simulators like Universe Sandbox or Gravity SImulator

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