Although he did not predict the position of Neptune, as did Adams and Le Verrier, Lexell's initial calculations of the orbit of Uranus showed that it was being perturbed and he deduced that the perturbations were due to another more distant planet.
Kahit na siya ay hindi mahuhulaan ang posisyon ng Neptune, bilang did Adams at Le Verrier, Lexell ng unang kalkulasyon ng orbita ng Urano ay nagpakita na ito ay ini-ligalig at siya deduced na ang perturbations ay dahil sa isa pang mas malayo planeta.