Absolutely stunning! I didn't know it was possible to make a better quiz that your "Name the strictly convex deltahedra" quiz but you came awfully close my friend! Keep it up
A very very good quiz. Great to see other astronomy fans out there! I would suggest you to reduce the time by 3 minutes, because it is too easy right now.
Saturn, Uranus, Neptune, and Pluto are given away by the "Type" column (and, to a lesser extent, Earth and Jupiter). You might just as well give the planets and make it the largest objects other than planets.
This quiz isn't meant to be especially difficult. I'm making the assumption that people who don't know the planets probably aren't going to get it from that column, but even if they do I don't think it's that bad. The planets don't seem to be the competitive part, given that all of them are typed in by ~98% of the quiz takers, but there are plenty of other more challenging answers that fewer people get. Thank you for the suggestion.
Oh dear, I have, some time ago, taken the Open University course "Moons of the Solar System" - thoroughly recommended incidentally - and failed to name more than one of Saturn's moons.
100% got Mars......