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About this collection

Dr. Clyde W. Tombaugh was born in Streator, Illinois in 1906. He was not long removed from the family farm in southwestern Kansas when he discovered Pluto in 1930 while working at Lowell Observatory in Flagstaff, Arizona. As a young man and amateur astronomer, Tombaugh began building his own telescopes. He eventually sent drawings to Lowell Observatory hoping for suggestions. Instead, the observatory was so impressed with his work that they eventually offered him a job, changing the course of his life forever.


Tombaugh earned a master's degree in astronomy from the University of Kansas and eventually received an honorary doctorate from Northern Arizona University. He enjoyed a long and industrious career as an astronomer, spending time at places like UCLA and White Sands Proving Ground in New Mexico before eventually helping to establish the NMSU Astronomy Department in 1970. He served as NMSU faculty and faculty emeritus for over twenty years until his death in 1997.


The Clyde W. Tombaugh Papers digital collection is a work in progress. At the present time it consists of selected materials from Tombaugh's life and career: family and other personal correspondence; professional correspondence; astronomical research and writings; and other items collected over the course of his life. The collection also contains large format items such as star charts, maps, and examples of his drawings. Click below to browse the document series.


                      Personal papers:                                                                    Professional papers:






See the Clyde W. Tombaugh online exhibit for more information regarding the physical collection, part of NMSU Library Archives and Special Collections.


New Mexico State University holds the copyright to the Tombaugh collection. For questions specifically relating to copyright compliance, please contact Associate Dean of University Library at 575-646-3279.


For best results, it is recommended that one of the following browsers be used: Google Chrome, Safari or Internet Explorer. If you have any general questions or questions about the re-use of these documents or images, or need assistance with any of our collections, please contact us at



                                                       Visual overviews of the collection's content are provided below:




Documents in this collection were created between the early 1900s and late 1990s. The years best represented in the collection are the late 1920s, the 1950s, 1960s and year of 1980. These years correspond to Tombaugh's work at the Lowell Observatory in Flagstaff, Arizona, White Sands Proving Ground in New Mexico, and New Mexico State University in Las Cruces. In 1980, Tombaugh celebrated the 50th anniversary of the planet Pluto discovery.




The pie chart above compares the percentage between two categories of Tombaugh's correspondence, personal and professional papers. At the current stage of the collection development, personal papers dominate the collection.






These two time line charts compare when personal and profesional papers originated. The graph shows that Tombaugh was exchanging personal letters over his entire adult life, while his professional correspondence aligns with his engagements with five institutions that he worked for in the 1940s through the 1960s. The White Sands Proving Ground and New Mexico State University are best represented in the collection to date. 








Two horizontal bar plots above display specific series of Tombaugh's corespondence and their volumes in personal and professional papers respectively. The charts allow for assessment and comparison of the specific series in terms of the number of documents they hold. 










Two aggregations of time lines presented above show when the documents in each series were created. 






The horizontal bar above compares volumes of letters written by most prolific authors. However, there is no bar for Tombaugh. Having written a massive number of letters, Tombaugh is off the chart. Interestingly, as represented in the collection, Tombaugh corresponded most intensely with his students.







The heat map shows who, among the most prolific authors, contributed to what correspondence series. This chart allows to identify quickly in what series one needs to look for a specific author.





 Pluto Discovery Anniversary series





Arizona State Teachers College series 



Two word clouds above display most frequently used terms in the Pluto Discovery Anniversary series, and the Arizona State Teachers College series, respectively. It is not difficult to see which subject Tombaugh used to teach at the college.






This set of time histograms shows annual counts for selected terms used in Tombaugh's correspondence over years. While terms like 'home', 'money', and 'photography' were often used over Tombaugh's lifetime, 'computer', 'missile', 'satellites' are more time-bound.





Tombaugh's fans across the world 





Tombaugh's fans across the United States 



Two maps above show the locations from which Tombaugh received fan mail. Each dot corresponds to a letter.





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