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

[Anders]

It's an amazingly unlikely system, but the galaxy has 100 billion stars. And if you set it in a galaxy far far away... there are 100 billion galaxies (at least!). If it's possible...

As for them all being Garden worlds - remember that you're probably not talking independent life origins on all the worlds. We have rocks from Mars on Earth, brought here through space. That kind of mechanism could seed life throughout the system.

[Phantasm]

The trick of course is getting the stars hot enough to have large life zones while still giving room for life to evolve on at least one of them. This puts the primary star roughly in the F4 to F7 range, in my amateur astrophysics opinion, with at least one other star being in the G2 to F8 range, and the other stars in the G3 to K7 range. It's possible, though IMO unlikely, to have stars as dim as M2 with garden planets should the planets be close together (I'm looking at you, TRAPPIST-1, with your three life zone planets that are likely tide-locked).

I would not use A-type stars as the primary, and I'm hesitant about F3 to F0 types. They don't seem like they'd last long enough.

[AlexanderHowl]

Planets within M-class stars habitable zones generally do not have moons, the orbits of the planets are too small, so the moons are stripped from their primaries and become independent objects (or crash into another planet, get kicked out of the system, get swallowed by the star, etc.).

[Pragmatic]

Originally Posted by Phantasm

The trick of course is getting the stars hot enough to have large life zones while still giving room for life to evolve on at least one of them. This puts the primary star roughly in the F4 to F7 range, in my amateur astrophysics opinion, with at least one other star being in the G2 to F8 range, and the other stars in the G3 to K7 range. It's possible, though IMO unlikely, to have stars as dim as M2 with garden planets should the planets be close together (I'm looking at you, TRAPPIST-1, with your three life zone planets that are likely tide-locked).

I would not use A-type stars as the primary, and I'm hesitant about F3 to F0 types. They don't seem like they'd last long enough.

In the old Space supplement (previous edition of GURPS?), I just added mass without increasing luminosity too much (and without reducing lifespan) by having close-binary stars.

If I recall correctly, that extended the "Goldilocks" zone, allowing a couple of habitable planets. I think I had to play with the albedo of the planets, but I was able to get a Cold planet and a Warm planet, or a Chilly planet and a Hot planet. Couldn't get two planets within the zone without one of them being slightly-off and the other being near-extreme.

The new Space supplement doesn't seem to allow combining the mass and luminosity of multiple stars.

[cptbutton]

Originally Posted by AlexanderHowl

The level of terraforming technology in Firefly is suspicious. How could they have not saved the Earth with that level of technology? It makes you wonder if they were just the malcontents who were exiled from the rest of human civilization, and that everything that people know about Earth-That-Was is a lie.

I put my thoughts on that here a while back:

Rationalizing a Firefly - Serenity type setting

tl;dr: Dangerous ultratech destroyed Earth-That-Was, so the colonizers used that ultratech to terraform the planets and then suppressed all knowledge of its existence because of the danger.

[Michael Thayne]

Originally Posted by AlexanderHowl

One thing to consider is that Medium and Large Gas Giants should probably have more possible major moons than Small Gas Giants, as they would attract more matter during their formation. I would suggest rolling 1d for major moons for Small Gas Giants, 2d for Medium Gas Giants, and 3d for Large Gas Giants. With that change, you could possibly have a quadruple system with 144 standard garden moons.

This is inconsistent with observations of our own solar system. It makes Jupiter ("large" gas giant, four major moons) unlikely, and Saturn ("medium" gas giant, one major moon) impossible.

Originally Posted by Anthony

I'm quite sure Whedon had no interest in such issues.

I agree, and meant to convey that. I really need to get more careful about my use of understatement.

Originally Posted by Phantasm

The trick of course is getting the stars hot enough to have large life zones while still giving room for life to evolve on at least one of them. This puts the primary star roughly in the F4 to F7 range, in my amateur astrophysics opinion, with at least one other star being in the G2 to F8 range, and the other stars in the G3 to K7 range. It's possible, though IMO unlikely, to have stars as dim as M2 with garden planets should the planets be close together (I'm looking at you, TRAPPIST-1, with your three life zone planets that are likely tide-locked).

I would not use A-type stars as the primary, and I'm hesitant about F3 to F0 types. They don't seem like they'd last long enough.

Huh. Looking at Wikipedia, the TRAPPIST-1 case is interesting, since the orbit of TRAPIST-1e is only about 1.32 times wider than that of TRAPIST-1d. GURPS Space sets the minimum at 1.4 (or 1.35 if you use the suggestion to "vary by 0.05 in either direction").

However, I suspect size makes no matter, because it does seem to be the ratio that's at issue--if the ratio is too small, the orbits won't be stable. I don't understand the details, "something something orbital resonance" is all I know.

[AlexanderHowl]

Jupiter is a medium gas giant according to Space (p. 124), so four major moons would not be that unusual. Jupiter is only 318 Earth-masses, and large gas giants are a mimum of 600 Earth-masses. Saturn is a Small gas giant (same page), though I argue against saying it only has one major moon. When you actually work through the formulas, any moon with a radius of 290 km to 450 km (depending on density) would qualify as a Tiny world. That would mean that Saturn possesses four major moons (Dione, Rhea, Titan, and Iapetus).

[scc]

Originally Posted by Phantasm

The trick of course is getting the stars hot enough to have large life zones while still giving room for life to evolve on at least one of them. This puts the primary star roughly in the F4 to F7 range, in my amateur astrophysics opinion, with at least one other star being in the G2 to F8 range, and the other stars in the G3 to K7 range. It's possible, though IMO unlikely, to have stars as dim as M2 with garden planets should the planets be close together (I'm looking at you, TRAPPIST-1, with your three life zone planets that are likely tide-locked).

I would not use A-type stars as the primary, and I'm hesitant about F3 to F0 types. They don't seem like they'd last long enough.

Increasing the size of the star to get a bigger habitable zone doesn't really work because you also increase the inner diameter at the same rate, so while the the size of the ring that is the habitable zone increase, the ratio remains the same.

[Flyndaran]

I have no clue, but wouldn't also that Goldilocks zone move outward faster for larger stars? Perhaps faster than life could adapt to even if the planet technically stays within the zone the entire time?

[AlexanderHowl]

The size of the habitable zone increases by the fourth root of L, so every 16x L equals a doubling of the habitable zone. Giant stars could be useful though, sort of like Darkover, as they can last a billion years, which is more than long enough to make worthwhile to terraform moons. A G2 giant would have a L of 40, meaning that the habitable zone would be at around 2.5 AU.