"Celestia doesn't tie you to the surface of the Earth, but
instead allows you to fly around the Universe in a First Person
perspective. You can travel at any speed you wish and can even
change the rate at which time progresses in the simulation. All of
the planets and moons have realistic orbits and are accurately
rendered using very accurate textures. Many of the known asteroids
and comets, such as Hale Bopp, are rendered using information from
NASA. The user interface allows you to follow an object as it
travels through space. By speeding up the simulation, you can
follow the orbit of Saturn around the Sun, as seen from Titan, one
of Saturn's moons, for example."
