From publisher blurb:
The Starsea Chronicles is a "hard" scifi companion setting to the core Starfinder The Roleplaying Game setting. Completely compatible, it offers several new races, galactic empires, and a slew of new items, technologies, ships, and vehicles for players and GM's alike. Also within are expanded concepts on world building and ship creation to help players to further diversify and expand on the material already provide. Jump into the Starsea Universe for a game full of endless possibilities.