Clyde Tombaugh Biography

Tombaughs task was to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. Using a machine called a blink comparator

The search for Planet X resumes when the Lowell Observatory director, Vesto Melvin Slipher, summarily hands the job of locating Planet X to Clyde Tombaugh

Tombaugh is assigned to systematically photograph the night sky and compare paired plates with a blink comparator in the renewed search for Planet X.

Tombaugh exposes one of the photographic plates later used, with the January 29 plate, to identify Pluto's motion.

Tombaugh exposes the second of the two photographic plates later used to identify Pluto's motion against background stars.

Tombaugh identifies Pluto as a moving object while comparing photographic plates taken on January 23 and January 29.

Using a blink comparator, Tombaugh identifies a moving object on plates taken January 23 and January 29, discovering Pluto.

News of Pluto's discovery is telegraphed from Lowell Observatory to the Harvard College Observatory.