Waving hands over my space opera setting
A bimodal globular cluster; Pop II stars, enough metallicity to support two-plus generations of colonies moving out from the first worlds settled, but marked with a Pleiades-like asterism of hot blue stars.
And that's where it stops being normal. Among those young stars is an exotic star, possibly a quark star (that Astronomy 101 class I took was long ago) that is doing peculiar things. I like the H.G. Wells of breaking one big thing then trying to play it straight after, and this is a big one.
This thing, Oberon, is causing clumping of dark matter (which it shouldn't ever do, at least from what little physics I know). What in-story are called solitons are forming, mutter mutter Robert Penrose, Twistor theory, which rip space. (And either hauling in interstellar gases and keeping the cluster from aging normally, or maybe fresh hydrogen is magically popping in around this stellar... thing.)
And let's pass over the mechanisms but basically mini transient wormholes are forming (when enough solitons clump in the same spot), making most of the impossible things of a space opera setting possible. Panspermia, and let's please ignore the math on that and just accept enough spores get through the holes from one supportive biome to another that you can have the forests of British Columbia on hundreds of planets. And they clump along a dendritic network spreading from the original hole, making space lanes you can FTL down if you have whatever combination of huge amounts of electrical power and a little bit of expensive exotic matter in your engine room.
So that's the ridiculously Earth-like planets, and the handy FTL which also passes down plot-convenient highways with equally convenient choke-points.
And, thematically, it means potentially dangerous things are happening to space time, coming out of this eldritch dark star thing. Plus a nice group of stars in the night sky everyone can look at and name the setting after.
I ain't writing hard SF. Modern space opera, Hornblower-esque with an early career (merchant) navy officer doing their thing out on the frontier, mining towns and pirates and all. But my protagonist is Engineer track, with "power gang" experience ship-board, and a dangerous talent of weaponizing the physics of the setting, so I do have to nail some of it down... at least well enough to set up the inevitable explosions.