Astrarium is a free and open source desktop planetarium software for Windows. It allows to discover night sky as seen from any point on the Earth and any date and time instant. There are many celestial objects can be observed, from eight major planets to faintest stars, asteroids and comets, deep sky objects, satellites and more; you can predict astronomical phenomenae, like phases of the Moon, planetary conjunctions and oppositions, as well as to get detailed information about object ephemerides.

Astrarium is written on C#, based on MVVM pattern and has extendable plugin architecture, that's why the full feature set of the planetarium depends on installed plugins.

Astrarium is a reincarnation of AcruSky Planetarium, started in 2008, but totally revised and rewritten according to a new concept.