+ Body &Root() noexcept { return root; }
+ const Body &Root() const noexcept { return root; }
+
+ const std::set<Body *> &Bodies() const noexcept { return bodies; }
+ const std::set<Planet *> &Planets() const noexcept { return planets; }
+ const std::set<Sun *> &Suns() const noexcept { return suns; }