Game

Moon Transit Catcher

Five of Saturn’s moons go round at their true relative speeds, sped up a lot. When the moon we name crosses in front of Saturn, hit Snap. You have 60 seconds.

The real thing

How long the big moons take to go round Saturn, in Earth days: Mimas 0.942, Enceladus 1.370, Tethys 1.888, Dione 2.737, Rhea 4.518, Titan 15.945. NASA NSSDC: Saturnian satellite fact sheet
Enceladus goes round Saturn twice for every once that Dione does. NASA Science: Enceladus
Their sizes, as radii in km (most are not perfectly round): Mimas 208 × 197 × 191, Enceladus 257 × 251 × 248, Tethys 538 × 528 × 526, Dione 563 × 561 × 560, Rhea 765 × 763 × 762 and Titan 2,575. NASA NSSDC: Saturnian satellite fact sheet
Average distance from Saturn’s centre, in thousands of km: Mimas 185.52, Enceladus 238.02, Tethys 294.66, Dione 377.40, Rhea 527.04, Titan 1,221.87. NASA NSSDC: Saturnian satellite fact sheet

Our game is a simplified model. The speeds are in the true ratio from NASA’s fact sheet, the moons are sized against each other and the A, B and C rings are drawn at their true size against Saturn, but the moons’ distances are squeezed to fit the screen and the orbits are drawn as tilted circles. In the game, a moon passing in front of Saturn is a transit; passing behind is an occultation.

Titan’s small orange globe in front of Saturn, with the rings seen edge-on — A real transit: Titan crossing in front of Saturn, from Cassini.Photo: NASA/JPL-Caltech/Space Science Institute, Public domain, Commons