Osmos is a fantastic game based around the concept of planetary orbits, and set in a relaxing ambient space environment. I highly recommend you try it when you're in the mood for a chill activity.
This is also very VERY NSFW, and I've been debating posting it for a few days because it's kind of gross and scatological and misogynistic, especially towards the end. But it's a catchy tune and in any case I couldn't really live with myself in a world where Marc and Vinny haven't seen such a superb videogame send-up.