Tag Archives: Pluto

Pluto at Ninety: Discovered, Demoted, Visited

A little more than ninety years ago, in a barred spiral galaxy named the Milky Way, a stellar system named Sol had a retinue of eight known planets revolving around it. The last one to be discovered was Neptune in September 1846. However, as time passed small perturbations in Neptune’s orbit were noted, which suggested another “trans-Neptunian object” existed whose presence altered his path around our Sun. It wasn’t until 1905 that a wealthy Boston astronomer, Percival Lowell, started a search for “Planet X” using his Flagstaff, Arizona, observatory. Lowell, with his mathematics background, and with the help of colleagues, tried to derive a possible orbit for a potential unknown planet. They even took photographic plates in 1906 of an area of sky where they thought planet “X” might be located, but with no results.

Unfortunately, Percival Lowell died at age 61 on November 12, 1916 and the search for the elusive “Planet X” ended. However, in 1929, the search for Pluto was resumed at the Lowell Observatory using calculations that Lowell had computed earlier. A 23 year-old Clyde W. Tombaugh was hired to meticulously image specific areas of the sky using photographic glass plates. The same star field would be exposed several days apart. Once the plates were developed, they were placed in a viewing machine called a blink comparator that held two plates. The operator could switch back and forth from one plate to the other. This process was called “blinking.”

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