Celestia

A open source planetarium simulation software for Linux. Linux has
quite a few planetarium simulation softwares like href="http://edu.kde.org/kstars/">KStars, href="http://stellarium.free.fr/">Stellarium and href="http://www.clearskyinstitute.com/xephem/xephem.html">Xephem.
But Celestia is both different and breathtaking.

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.

Take a look a the href="http://ennui.shatters.net/celestia/gallery.html">gallery
to understand what I’m talking about.

From href="http://celestia.sourceforge.net/">celestia.sourceforge.net.