Pluto Discovery Collection At State Library

In celebration of NASA’s New Horizons spacecraft exploration and the 85th anniversary of Pluto’s discovery, Lowell Observatory has posted a collection in the Arizona Memory Project, an online program of the Arizona State Library, Archives and Public Records. The collection, “Year of Pluto,” includes letters, calculations, photographs and documents that illustrate the history of the search for Pluto, its discovery, and the subsequent public excitement and fascination.

“Excitement about Pluto is exploding as New Horizons continues to send photos about Pluto and the most outlying part of our solar system,” said Secretary of State Michele Reagan, whose office oversees the Arizona State Library. “We are so excited Lowell Observatory has shared items showcasing the exhilaration the discovery of Pluto ignited all over the world.”

In addition to the Arizona Memory Project, archived newspaper accounts about Lowell Observatory, where Pluto was discovered, are available online with the Arizona Digital Newspaper Program; including an entry from the Arizona Republican from Nov. 3, 1909, “Flagstaff the Center of Planetary News.”

If you crave more, call the Arizona State Archives to access files on Ft. Lowell Observatory; biographical information on the man who discovered Pluto, Clyde Tombaugh; and more in the Arizona Collection. For more information, contact 602-926-3720.

The Arizona State Library, Archives and Public Records, a division of the Secretary of State, helps Arizonans know and obtain information about their government, their state and their world. We provide expertise to empower informed decisions. For information of all of the State Library programs, go online to The Arizona Memory Project and the Arizona Digital Newspaper program are made possible by federal funds from the Institute of Museum and Library Services. For our full collections, visit us online at and The Arizona State Archives and Records Management collects, preserves and makes available to the public: permanent public records, historical manuscripts, photographs and other materials that contribute to the understanding of Arizona history. For a full range of services, visit the Archives online at

Lowell Observatory is a private, non-profit research institution founded in 1894 by Percival Lowell. The Observatory has been the site of many important discoveries including the detection of the large recessional velocities (redshift) of galaxies by Vesto Slipher in 1912-1914 (a result that led ultimately to the realization the universe is expanding), and the discovery of Pluto by Clyde Tombaugh in 1930. Today, Lowell’s 14 astronomers use ground-based telescopes around the world, telescopes in space, and NASA planetary spacecraft to conduct research in diverse areas of astronomy and planetary science.


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