Celestia Portable

Celestia Portable is a virtual planetarium available for free. You can store it on any USB or extractable portable drive. Celestia has a large database of planets, stars, and other celestial bodies that you can visit by moving in space and zooming in. With Celestia, you can view space from Earth, and also use it to see celestial bodies from different external perspectives. Another great feature is the ability to increase the number of visible objects with 'add-ons' created by other program users.