Credibility Kills!

 Kills what? RP hooks mainly.

On various forums I have seen a never ending hunt for rules to design better and more accurate star systems, in accordance with then latest astronomical data. Let me throw cold water on this right now: your players care a lot less about this than you think. 

I wrote Solar Sagas, a planetary setting in the Old Solar System where everything was (at least marginally) habitable, in the tradition of Golden Age SF. I didn't get burned in effigy (that I'm aware of). 

Discussion on one forum turned to a habitable planet around a white dwarf star. The OP got little encouragement for it. I remembered some articles I read and started hunting (Perplexity really makes this job easier). Sure enough the good old space telescope found a number of planets and other objects orbiting  white dwarfs. One planet was even in the Goldilocks Zone. 

To give the detractors a fair chance, the articles pointed out many problems with a habitable world. For one thing the expansion to a red giant and collapse to white dwarf would blow a planet's atmosphere away and boil its oceans. It would need a magnetosphere a million times stronger than Jupiter's to avoid this. 

However, I have yet to enter such a debate without it turning slowly against the credible arguments. Suppose we have an extremely massive, hot star, that burns through its fuel in a fraction of a billion years. It might have planets still forming, still experiencing outgassing that forms the basis of an atmosphere. The star explodes and collapses. The planet migrates inward. Outgassing continues and a primordial atmosphere forms. 

Such a planet would experience tidal forces, but this might increase internal warming, agitating the core and producing a strong magnetic field. This field protects the atmosphere somewhat from flares. The planet would be terribly close, and tidally locked. But those are old hat for type M stars. 

But it is just barely possible. Maybe a referee special, one to a campaign. Don't bother rolling. Stick one wherever. Just one. 

Life forms would be tough, adapted to high radiation, seismic upheavals, extreme weather, and ghu knows what else. Humans attempting to settle there would probably have little contact with the rest of the galaxy. A white dwarf the size of Earth would mass the same as the Sun. If you're using 2D6 jump drives the jump limit is just shy of one astronomical unit -140 million kilometers. Even for reaction less drive ships, this is a non trivial ship. There are plenty of worlds outside this limit with transit times measured in days or hours. It might be a good location for a secluded colony or research base.

Such a planet might go mostly unnoticed. After all the surveys the exploration arm does, turning up nothing interesting around hundreds of other white dwarfs, would they bother looking too closely at yet another? They might tag it for a followup when they're not busy, and look loser when they aren't rushed. Tentative bio signature? Probably a glitch, abiotic formation of organic molecules. We'll get to it.

The military determines pretty quickly there are no gas giants and likely little volatiles left in what looks like the embers of a star system. They don't go there.

Merchants go where the money is. Seeking out strange new worlds? Not their job.

Misjump? Now we're talking. Lots of religions and factions out there looking for a secluded hideaway.

Is it likely? No. but unlikely and the jumping through hoops to make it happen make some fun stories.