They realized that there must be a distant, giant planet just beyond the orbit of Uranus that was tugging along at that orbit, sometimes pulling it along a bit too fast, sometimes holding it back.
Eles perceberam que devia haver um planeta gigante e distante, além da órbita de Urano, que puxava aquela órbita, ora a puxava um pouco rápido demais, ora a segurava.