App: Solar Walk (Buy it for iOS here)
Price $2.99.
The Solar Walk app includes an interactive model of the galaxy. You can tap on planets and stars to learn about their trajectories, structural make up, and the history of their exploration. The app also lets you plug in a specific date, past or present, and it will display how the planets were aligned. Solar Walk also has 3D models of some of the man made satellites orbiting in space.