from the Web page:

Celestia is a free real-time space simulation that lets you experience our
universe in three dimensions. 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. All travel in
Celestia is seamless; the exponential zoom feature lets you explore space across
a huge range of scales, from galaxy clusters down to spacecraft only a few
meters across. A 'point-and-goto' interface makes it simple to navigate through
the universe to the object you want to visit.

WWW:  http://www.shatters.net/celestia/ 
