Starfield has about 120 star systems that you can visit, each with their own planets, moons, and many other points of interest like cities and settlements, and sometimes even entire quest lines. Though you’ll spend the first few hours cooped up in a small cluster of stars, once you get a better ship or upgrade your Grav drive, you can start jumping to more distant systems with higher-level caps.
Starfield: 15 Best Solar Systems, Ranked
While you're casually exploring the hundred-plus solar systems in Starfield, don't forget to visit these ones; they're the best systems in the game.