Celestia is an open source, 3D astronomy program for Windows, Mac OS X, and Linux created by Chris Laurel. The program allows user to simulate objects ranging in scale from the International Space Station to the Milky Way Galaxy in three dimensions using OpenGL. Unlike most planetarium software, the user is free to travel about the Universe. Over 10GB of add-on content is available to supplement the basic program as a result of the small, but productive community of users that support the program. NASA and ESA have used Celestia, but it is not to be confused with Celestia 2000, ESA's own program.

See also: List of open-source software packages

External links

• http://www.shatters.net/celestia/
• http://www.celestiamotherlode.net/ - collection of add-ons made by various people
• http://en.wikibooks.org/wiki/Celestia - Celestia wikibook
• http://learn.arc.nasa.gov/planets/ - NASA's page on Celestia
• http://www.esa.int/esaCP/SEM4GC374OD_Ireland_1.html#subhead2 - instance of ESA using Celestia