Free Astronomy Magazine January-February 2020

12 JANUARY-FEBRUARY 2020 HISTORY to previous failures, and Tombaugh had practically started his own research pro- gram. Between Sep- tember and October 1929, the tenacious amateur astronomer photographed star fields in Aquarius, Pisces and Aries, while in November and December, he concentrated on the constellation Taurus. In January 1930, Tombaugh began to re-photograph the constellation Gem- ini, already pho- tographed eight months earlier. Now, however, it was in op- position, and somewhere there should have been the Planet X yearned for by Lowell. It was therefore unavoidable to photograph of the sensitive support, and other noises. Not knowing how Planet X might have ap- peared, it is clear that, if it had a stellar ap- pearance, it would have been almost impossible to make the neces- sary checks on all those non- fixed objects. Frustrated by this situation and homesick for the remoteness of his land, Tombaugh became very sad, to the point that Lamp- land granted him a long vaca- tion to spend with his family. The fear of never seeing him return to Flagstaff was strong. Instead, in the autumn of 1929, Tombaugh returned to the observatory to restart, more motivated than ever, the search for Planet X. To speed up his work he had thought to photograph the regions of the sky in opposi- tion, where it was easier for him to estimate the distance of a body in motion, starting from the length of the path between one photographic exposure and the other. Low- ell’s prediction had now faded into the background, also due C lyde Tombaugh at work with the blink comparator which high- lighted Pluto's motion in the sky. Below, the same instrument dis- played today as a relic at the Flagstaff Obser- vatory. [Lowell Observatory Archives]