If you like space, stars etc you definitely should testCelestia – a space simulator. It lets you explore our universe in three dimensions. Celestia runs on Windows, Linux, and Mac OS X. So, you can choose your preferable OS.
Unlike most planetarium software, Celestia doesn’t confine you to the surface of the Earth. You can travel throughout the solar system, to any of over 100,000 stars, or even beyond the galaxy.
Additionally, you may check the Celestia Motherlode – a repository for various addons like textures, models or celestial objects for Celestia.