[ Thanks to An Anonymous Reader for
this link. ]
“Celestia is a real-time visual space simulation
astronomy program. It is a cross platform, open source software and
released under the GNU General Public License. NASA and ESA have
used Celestia in their educational and for interfacing to
trajectory analysis software. It allows users to travel through an
extensive universe, modeled after reality, at any speed, in any
direction and at any time in history. Celestia displays and
interacts with objects ranging in scale from artificial satellites
to entire galaxies in three dimensions using OpenGL. It is a
perfect software for astronomer, educator, student, and teacher for
astronomy purpose.”