First up is Celestia. It's a multiplatform tool for exploring our galaxy. All of it. You can jump around between stars, zoom into planets, moons, asteroids, existing spacecraft, etc. It lets you speed up or slow down or go backwards or forwards in time. In short, it's an astronomy program for exploring everything. The basic download will get you going very nicely, but there's tons of awesome add-ons to make it even better. However, installing them can be somewhat less than intuitive.
The other tool is StarGen. There are both Mac and Windows versions of the stand-alone app, plus a link to a web-based version. It generates solar systems with pretty complete data on each planet. You can have it filter output to only systems with Earth-like, or potentially habitable planets. I gather that the method it uses isn't up to date with current planet-formation theory, but it does still produce good results for storytelling purposes.
I've personally used Celestia extensively when working on science-fiction worldbuilding (specifically a story set on a terraformed Ganymede). It was invaluable for getting a sense of the way day/night cycles worked and figuring out the timing of daily eclipses.
The other tool is StarGen. There are both Mac and Windows versions of the stand-alone app, plus a link to a web-based version. It generates solar systems with pretty complete data on each planet. You can have it filter output to only systems with Earth-like, or potentially habitable planets. I gather that the method it uses isn't up to date with current planet-formation theory, but it does still produce good results for storytelling purposes.
I've personally used Celestia extensively when working on science-fiction worldbuilding (specifically a story set on a terraformed Ganymede). It was invaluable for getting a sense of the way day/night cycles worked and figuring out the timing of daily eclipses.