[Space] Star system with thirty-six inhabitable worlds?

[Michael Thayne]

Here's a fun exercise: according to the letter of the rules in GURPS Space, what the maximum number of inhabitable (i.e. Garden) worlds you can have in a star system? This isn't about what's likely, just what's possible, if you are carefully picking the results of every die roll to produce the desired result. I think the answer is thirty-six, but I'd like to have other people check my reasoning.

I don't see anything in the rules to stop you from having three nearly identical stars in a system. Lets suppose they each have a mass of 1.25 that of Sol, and furthermore the system is 4.1 billion years old. That yields a luminosity of 3.2. We'll also assume the two stars closest to each other orbit about 8 AU apart, while the third star orbits 16 AU from the combined center of mass of the first two. The snow line will be located at 7.03 AU. Suppose each system has eccentric gas giants, and among other things has gas giants at about 1.6 and 2.24 AU. These—and crucially, their moons—will have blackbody temperatures of 294K and 248K. If every gas giant has six moons and all are standard or large garden worlds, that's 3 stars x 2 gas giants per star x 6 moons per gas giant = 36 habitable worlds.

Of course, this is a wildly unlikely result, but it does somewhat suggest a strategy for building a star system where the number of habitable worlds is large but won't immediately be noticed by your players as requiring completely absurd coincidences. Unless I've missed a rule that would prohibit the above—have I?

[AlexanderHowl]

That seems good. It is highly likely that it is a terraformed system though.

[Michael Thayne]

Originally Posted by AlexanderHowl

That seems good. It is highly likely that it is a terraformed system though.

More than terraformed, I'd say. More like "the Precursors rearranged the entire system for their inscrutable reasons".

[Diomedes]

You can probably get up to five stars, not three:

Originally Posted by GURPS Space, p105

A distant companion may have a companion of its own, on a roll of 11 or higher on 3d. This is the only way to get more than three stars in a multiple system when using the random-generation method. If so, the companion is treated in all respects as the primary star for its own companion. Generate stellar characteristics for the “subcompanion” as in Step 15.

This would result in three distant systems, two doubles and a single.

[AlexanderHowl]

Octuple systems are probably the largest where every star could have stable planets, and I am not sure we have seen any. For example, you could have two pairs, each pair with a separation of 120 AU between the two partners, with a separation of 720 AU between the two pairs, and an second identical two pairs with a separation of 3600 AU from the first two pair. Anything higher order than would break away from the system after a few hundred million years.

[martinl]

Originally Posted by Michael Thayne

but won't immediately be noticed by your players as requiring completely absurd coincidences

You have a higher standard for completely absurd coincidences than I do.

[Michael Thayne]

Originally Posted by Diomedes

You can probably get up to five stars, not three:



This would result in three distant systems, two doubles and a single.

Oh huh, I've been ignoring that rule this whole time whenever I roll up multiple star systems.

Originally Posted by martinl

You have a higher standard for completely absurd coincidences than I do.

I'm not sure if this means you think 10 garden worlds in a star system is still completely absurd, or that a star system consisting of three identical sub-systems orbit each other is completely absurd.

[Anaraxes]

Since the system gives you exact probabilities thanks to it being rules and tables for dice, you could calculate the exact degree of absurdity in your coincidence.

[johndallman]

Originally Posted by Michael Thayne

. . . won't immediately be noticed by your players as requiring completely absurd coincidences.

I wouldn't use such a system. Players would immediately be sure that it was artificial, and would regard the mystery of how it came about as fascinating. This would distract from any other kind of story set there.

[Flyndaran]

If all other systems in the setting are more realistic, then I'd question the curiosity of the players if they didn't assume this one was artificial.