Tombaugh’s search involved photographing the night sky through a powerful telescope. He then had to minutely examine pairs of photographs using a piece of equipment called a blink comparator. The aim was to detect whether any of the bodies in the images had moved. And he was to be absorbed in this repetitive task for almost a year before a breakthrough came.
Tombaugh’s moment of triumph arrived on February 18, 1830, as he studied photographic plates that had been exposed in January of that year. More photographs were then taken to confirm the findings, and the discovery of this yet-to-be-named planet was announced to the world on March 13, 1930.