I'm writing a soft science novel and have bumped my head on hard science. I need to know if an earth sized planet could be placed in orbit in our system, without destroying it or Earth. Minimum time in orbit would need to be one year. (In the book the planet could be moved if it became unsafe.)

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    $\begingroup$ Earth is a very tiny planet compared to Jupiter and Saturn. If the orbit of the new planet is separated from all other orbits by a larger distance, the orbit will be stable for a much longer time than only a year. $\endgroup$ – Uwe Aug 18 '19 at 18:20
  • $\begingroup$ Start with this, maybe? $\endgroup$ – Oscar Lanzi Aug 18 '19 at 19:44
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    $\begingroup$ I'm voting to close this question as off-topic because I don't see any connection to real world space exploration - the topic is purely fictional. We won't be moving planets around any time soon. Feel free to reword your question if it can be made to fit better. Maybe better fit on worldbuilding stack exchange? $\endgroup$ – Organic Marble Aug 18 '19 at 20:13
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    $\begingroup$ @OrganicMarble I think it is ontopic on the WB, the question is, is it ontopic here. Maybe if the question would be about the theoretical possibility of such exoplanet systems? Btw, the currently most accepted scenario for the creation of the Moon is some quite similar. $\endgroup$ – peterh - Reinstate Monica Aug 18 '19 at 20:46
  • $\begingroup$ A more general question about stability (and what it means) in planetary systems would be 100% on-topic in Astronomy SE. That may be a much better site to get answers strictly based in hard science and vetted by other scientists. There's nothing wrong with stating your purpose, but the nature of the question should be about a pair of Earth-massed planets in similar orbits in general. Fyi there is a possibility of orbital resonance which could ensure that they never get too close to each other over millions of years. $\endgroup$ – uhoh Aug 18 '19 at 23:58

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