Simplify the following text for a Grade 10 native English-speaking person.
Original: On February 18 , 1930 , after nearly a year of searching , Tombaugh discovered a possible moving object on photographic plates taken on January 23 and January 29 of that year .
Simplified: On February 18 , 1930 , Tombaugh discovered an object which seemed to move from the photographic plates taken on January 23 and January 29 of the year .