It's a fun sandbox to play around with and the gravity physics are really well done, so I'd say you did a good job :)

It was fun building out the solar system

The gravity mechanics are well done and super fun.  I don't quite know what to do to win, but I had fun just placing the different items and slowly discovering how they work.  (For a game jam, you might want to add instructions in the game description as other testers tend to give very little time).

I enjoy gravity based games like this. May I ask if you used Unity's Rigidbody physics gravity/mass or did you program in your own?