Free Astronomy Magazine January-February 2020

13 JANUARY-FEBRUARY 2020 HISTORY Planet X had finally been captured. The days that followed the discovery were fran- tic. Mindful of the previous poor figures made by the observatory, Lampland, the Slipher brothers, and Tombaugh himself decided that before giving the announce- ment of the discovery it was essential to produce other im- ages and observa- tions. On 19 Feb- ruary, it was estab- lished that Tom- baugh would con- tinue to expose plates around Delta Geminorum with the 13-inch astrograph, while Lampland would use the 42-inch reflector to take higher magnifica- tion images cen- tered on the plan- et in order to make accurate position measurements. Of course, the inten- the entire region again. After the Last Quar- ter Moon, on 23 and 29 January, Tombaugh took two plates around Delta Geminorum, which he put in the blink only in mid-Febru- ary. On those plates a stellar-looking object had moved at a speed compatible with that of a possible trans-Neptunian planet. C lyde Tombaugh's original images identifying Pluto in 1930. The tiny, faint dot moves very slightly rela- tive to the back- ground stars, but sufficiently so that we've been able to success- fully reconstruct its orbit. [Lowell Observatory Archives] Alongside, the announcement of the discovery of Pluto given by the newspaper THE WORLD on March 14, 1930: “Years of search add new planet to Solar System’, “Astronomers Announce Discov- ery of Body Four Billion Miles From Sun”.