Celestia is a free real-time space simulation that lets you experience
our universe in three dimensions. Unlike most planetarium software,
Celestia does not 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.