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The habitable planets will be very similar in size to earth and are on separate orbits orbiting a Sun-like star exactly the size of our own Sun. How many habitable planets can I fit into the habitable zone of my star and still stay stable for millions of years, without the orbits intersecting due to gravitational interaction?

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  • $\begingroup$ Welcome to WorldBuilding! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$ – Secespitus Jun 13 '18 at 7:32
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    $\begingroup$ I'm pretty sure I've seen a question very much like this before, but can't seem to find it with a quick search. $\endgroup$ – a CVn Jun 13 '18 at 7:36
  • $\begingroup$ I'm pretty sure I have seen this asked before. I was able to find one about Mars-sized planets: worldbuilding.stackexchange.com/q/54962/809 $\endgroup$ – Mołot Jun 13 '18 at 7:38
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    $\begingroup$ planetplanet.net/2014/05/23/… Got 60 using various tricks like having several habitable moons of orbiting gas giants. $\endgroup$ – Donald Hobson Jun 13 '18 at 8:39
  • $\begingroup$ Since humanity started to regularly find exoplanets and mapping other star systems, the stranger orbits and planets we discover, maybe the better question would be how many do you need for your story, as you can greatly increase the number of planets by changing the eccentricity of some of there orbits. like Pluto is on a highly eccentric and elliptic orbit, it manages to miss the other planets it passes, the same could be true for planets in the Goldilocks zone $\endgroup$ – Blade Wraith Jun 13 '18 at 9:39
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Given our solar system as a model, you could fit three of them, jackpot!

Venus was a very unlucky planet -hypervolcanic activity, perhaps connected to the mechanism that inverted its rotation helped create its hellish atmosphere. But without those factors, it could really be a tropical paradise.

In Mars' position, you could throw in a planet with just enough mass for the core to rotate nice and strong, have your gravity and magnetic field protecting the atmosphere and voilĂ ! A little cold but definitely inhabitable.

Overkill: A binary Earth and that would make four planets good to call home

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I wrote an extensive series of blog posts to answer this question: https://planetplanet.net/the-ultimate-solar-system/

Jumping to the punchline -- based on orbital stability alone it is possible to pack several hundred planets in the habitable zone of a single star (see https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/).

From https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/

(Or a million if you incude a supermassive black hole: https://planetplanet.net/2018/06/01/the-million-earth-solar-system/)

Systems that are more likely to form naturally can easily have up to 5-10 worlds in the habitable zone.

Happy to answer any other questions on this. I've found that it helps people to trust me to mention that I'm an astrophysicist and orbital dynamics is my specialty.

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    $\begingroup$ See? If God existed, he'd do some SERIOUS work instead of taking only 6 days for one meager planet and then resting! $\endgroup$ – Valerio Pastore Jun 13 '18 at 10:36
  • $\begingroup$ Sean, this answer is very good. Since the original question is closed as a duplicate, do you want to copy this answer to that question? $\endgroup$ – kingledion Sep 7 '18 at 23:58
  • $\begingroup$ Thanks for the heads up kingledion. I just copied it over. Cheers! $\endgroup$ – Sean Raymond Sep 10 '18 at 7:31

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