[SPACE 4e] System Design help? (star systems that is...)

[dataweaver]

I'm not sure how likely this is; but consider the Trojan points. It seems reasonable that if you get stable enough L4 and L5 points in the orbit of a brown dwarf, and enough mass accumulating there, you might get terrestial planets to form. Place one in each Trojan Point and one in orbit around the brown dwarf, and place the brown dwarf in the primary's habitable zone, and you can get three habitable worlds.

Note that this may not be feasable: it depends on the amount of matter that's likely to pool in the Trojan Points. I suspect that the more massive the brown dwarf, the more mass is likely to pool - except that the more massive the brown dwarf, the less stable its Trojan Points will be (maximum mass for satellite with stable trojan points = 4% of primary's mass). This option may be no more likely than a natural Rosetta (or it may be far more likely; I don't know); but it is an option that has the virtue of being unique: I have never seen anyone try it.

I'd design the terrestrial worlds according to the Basic Worldbuilding rules; I'd then place all three in the same orbit: one orbiting the brown dwarf, and one in each of the two Trojan Points. The main sticking point will be the worlds' climates: hold off on determining the worlds' atmospheric masses in Step 3. Instead, determine the blackbody temperature for the orbit that all three worlds will be in; divide each world's average surface temperature by this common blackbody temperature to get its Blackbody Correction Factor; then reverse-engineer the atmospheric mass from that:

atmospheric mass = (blackbody correction factor / world's absorption factor - 1) / world's greenhouse factor.

This can then be used to finish establishing the world's atmospheric properties.

Note also that the world orbiting the brown dwarf has the potential to see vast changes in climate, depending on how far out it orbits the brown dwarf: get it far enough away, and it will be swinging from the inner edge of the primary's habitable zone to the outer edge. Depending on how warm the brown dwarf is, you might even get additional heating from it, possibly enough to render the inner surface's climate Infernal while the outer surface fluctuates between Hot (during the day) and Cold (at night), or Warm and Cool.