Project: svg-solar
Task (challenging): We call the collection of star and planets as `star-planets` view. Click planet to clear systemRoot and systemDefs, and show planet at system center in systemRoot, all satellites(data from `body.bodies`) and its orbits just like `star-planets`. We call this new collection of planet and satellites as `planet-satellites` view. Make sure the minimal radius of planet is 8 in `planet-satellites`.