I'm wondering how close a planet-M-dwarf system could orbit a G star and have the planet remain tidally locked to the M star. I'm curious, because I'm designing a habitable planet, and I want the planet to be close enough to the G star that at least a minimal amount of photosynthesis could occur on the "night-side" (not really accurate term in this context). If the planet-M-dwarf system was orbiting the G star at 2 AU, could the planet remain tidally locked? If not, what is the minimum distance?

  • $\begingroup$ It depends how close the planet orbits the m-dwarf. It is debatable whether a tidally locked planet is habitable. With 2au separation between the stars hardly any orbit will be stable $\endgroup$ Sep 21, 2022 at 17:30
  • $\begingroup$ Ok thank you, that's what I thought, but I was hoping there was a way around it. $\endgroup$
    – Elhammo
    Sep 21, 2022 at 18:42


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