Celestia 1.6.4

Celestia is a powerful simulator for exploring the Universe. It comes with an accurate tool for details, and high functionality. You can zoom in/out at any time, set locations, explore various planets, moons and constellations. Also in the left upper corner, the application constantly displays parameters like distance, radius, apparent diameter and phase angle. You can set up how fast you want to travel between planets, stars or celestial objects and have various speeds to choose from: 1 km/s, 1000 km/s, light speed (c) or multiples of 'c'. For a better understanding of the movement of planets, you can choose to display orbits and/or grid. Also, this feature-rich application comes with a self-explaining demo, that takes you on a general tour around the Milky Way, presenting the most-known planets. As you discover new planets or stars, you can set each one of them to be a central point, or bookmark it for future references.

All taken into consideration, you should give Celestia a try; it is a free space simulator which allows you to freely explore various planets, stars, constellations or celestial objects.