I was thinking of having the binary planets in my fictional solar system (Kepler Db(Mars like) and Kepler D#(Venus like)) have a moon. Life is on both of these planets in intelligent humanoid forms, but different from the humanoids on the 2 earth-like planets. For 1 the humanoids on Kepler D# depend more on acid and minerals and they use HCl and HF as their water(With so much pressure, a gas at room temperature can easily become a liquid or even a solid). They also eat lava for their minerals since they can't digest solid rock easily. Because of this they are extremely heat resistant and it would take surface of sun temperatures to significantly burn themselves. They also get their body heat primarily this way so they are sort of between warm and cold blooded. Now anyway would a figure 8 orbit around the 2 planets be stable or would this eventually lead to rings on 1 of the planets or a big crater(depending on gravity)? This would lead to these 5 types of eclipses: Solar eclipse(either from planet or moon) Double solar(Both blocking the star system from view Lunar + Solar(most likely a planet blocking the star system and the moon being blocked Double lunar(Both being blocked by the shadow of the planet) Lunar(Again, either from planet or moon) So would this figure 8 orbit be stable as long as the moon stays outside the roche limit of both planets?