Solar System Generation
The standard Traveller world generation only generates one world per system so what does that mean in game terms.
The science of solar systems is roughly: a solar system has a star (sometimes more than one) from one of a collection of star types and around the star there are multiple orbits which may contain a planet of some kind. These orbits are divided into three zones: inner zone which is too hot for water; outer zone which is too cold for water and a potentially habitable zone in between. The size of the three zones depends on the heat of the star.
For example imagine two solar systems both with 12 orbits, one star is weak and so has say 2 inner orbits, 2 habitable orbits and 8 outer orbits; the second star is hot and has say 4 inner orbits, 4 habitable orbits and 4 outer orbits.
Gas giants form in the outer zone.
Weak stars whose habitable zone is relatively close to the star are more likely to have planets that are within the star’s 100 diameter jump shadow and more likely to be tide locked
Advanced Generation Systems
There are lots of more advanced world generation systems that create the whole solar system:
GURPS “First In”
MegaTraveller “Would Builder’s Handbook”
“Universe” scifi RPG
“Rogue Trader” from Warhammer 40K (my personal favorite)
however for the most part unless your campaign is very heavily focused on exploration this is going to be much more work than you’ll need.
So in game terms we can say that the Traveller world generation system generates the *best* planet in the system.
A follow on from the idea that the world generated is the most habitable is that a system might have other planets that are not as good.
A quick way to generate this is if a generated planet has good physical stats roll a second time – if the world generated is worse make a note and then roll again until you don’t get a worse one.
Example: generated world has 866 physical stats; roll again and 440; roll again 310; roll again 520 – the 4th is better than the 3rd so drop it leaving three: 866, 440, 310
Another follow on from the idea that the world generated in the standard system is the most habitable planet in the system is you can work backwards from the world to generate the solar system.
Mongoose Traveller: “Scout” has a good system for doing this.
In most cases treat the world generated as the best in the system and don’t worry about the rest of the solar system unless needed and if available use the relatively quick and simple Mongoose “Scout” method of working backwards from the world.
In a campaign centered around exploration, either an early colonization campaign or a “five year mission” type campaign I’d suggest using the Warhammer 40K “Rogue Trader” system as that throws up navigational hazards which can be used as Star Trek like “anomalies” to investigate.