This article is a rebuttal to the assertions contained in the scifi channel’s Lab Notes discussion of the Serenity universe, and the subsequent thread on whedonesque. Simply put, one does not have to invent an improbable solar system to achieve the number of habitable worlds present in the movie/series.
The Geneva-Copenhagen survey that observed more than 14,000 F and G class stars over a 20 year period showed that stars ranging from 0.7 to 1.5 solar masses were the most common, with the bulk of stars occuring between 1 and 1.5 solar masses. Therefore, it is probable that a solar system chosen for inhabitation would have a star that was somewhat larger (and thus, presumably, formed in a larger accretion disk than our Sun.)
Our solar system supports four gas giants. The two largest constitute 0.1% and 0.3% of the mass of the solar system.
Therefore, if we were to linearly scale the solar system to match that of a star of 1.5 solar masses (of which there are more than 1000 within our spiral arm) we would have gas giants that were 1.5x the size of ours.
Jupiter has 63 moons of which the four largest are io (3,600 km dia) Europa (3,130 km), Ganymede (5,286 km), and Callisto (4,800 km). Increasing that by a factor of 1.5 gives us three moons larger than mars and one nearly that size.
Saturn has 46 moons, Uranus 27, and Neptune 13. Saturn would get one larger-than-mars moon (Titan), and two (Dione and Rhea) that would be larger than earth’s moon.
Oberon and Titania of Uranus both respectably exceed 1400km in diameter, or over 200km in our erstwhile system, and Triton of Neptune is another giant, with its 2700km.
A significant number of the smaller moons would be above 1000km in diameter in our expanded system.
We know that the Serenity universe has gravity generation and, evidently, reaction-mass-free propulsion. The first fact would explain why so many of the moons in the serenity system were terraformable, because the primary constraint on terraforming is the planet’s ability to hold in an atmosphere.
The massless propulsion provides justification for why a culture departing earth could choose such a fecund system, regardless of whether it was a few thousand light years away; they have delta v to spare, and thus can follow a simple relativistic course to a foreign system and experience relatively little time passing (though obviously they also have cold-sleep).
Finally, all the current planetary systems we know about contain gas giants much larger than those found in our solar system. Future colonizers, while they are likely to have better resolution than our methods, are still likely to find systems with larger-than-average gas giants.
These gas giants are extremely likely to contain more and larger moons than our own set. Furthermore, the larger the gas giant gets, the less it matters whether you are within the ‘habitable band’ that surrounds the star, because radiant heat from the gas giant will make up for whatever thermal loss you might suffer.
Indeed, based on the diagram placed on the screen briefly in Serenity, one suspects that there is simply one inhabited gas giant system, and it happens to have, say, 100 or so moons of which 40 or so have been terraformed. Another likely scenario is three habitable inner rocky worlds (controlled by the Alliance) and a variety of moons around the gas giants inhabited by all the other folk we see.