Noun: An
absolutely fucking sweet kick-ass space simulator that not only contains the solar system, but comes with some extrasolar planets and the ability to create your own stars, solar systems, nebulae, galaxies, and
practically any other space object you can think of.
Ideal for world-builders, astronomy enthusiasts and utter nerds.
What's more, it's freeware. Get it from www.shatters.net/celestia.
The latest version is hard to find but worth
downloading, as it accurately represents binary stars.