Since version 0.9.9.0, SpaceEngine has transitioned to a paid model on Steam. This supports the lone developer (Vladimir Romanyuk) and ensures the project continues to grow.
However, if you are looking for a free way to explore the universe, the developer still hosts version 0.980 official SpaceEngine website space engine 0990 download free upd
: Integration of the latest NASA data for newly discovered worlds. Performance Optimization Since version 0
If you've already purchased the game, here's how to update to version 0.9.9.0: Since version 0.9.9.0