Discovering Pluto at Lowell Observatory

The Lowell Observatory was founded in Flagstaff in 1894 by astronomer Percival Lowell, known for his research on Mars. In 1930 amateur astronomer Clyde Tombaugh discovered Pluto using the observatory's astronomical camera at. Pluto is named for the Roman god of the underworld, and in Roman mythology Pluto’s brothers are Jupiter and Neptune. In 2006 the International Astronomical Union voted to remove Pluto's status as a planet after further research showed its composition and orbit are too different from the other planets.

Read About It

Use the document analysis sheet and the photograph analysis sheet to uncover clues about the people that created the documents.

• "The Lowell Observatory," Arizona Weekly Citizen, July 7, 1894 (p. 2, column 8)
• "Lowell's Observatory World Famous," The Coconino Sun, Jan. 6, 1911 (p. 1, column 5)
• "Dr. Lowell Passes Away," The Holbrook News, Nov. 17, 1916 (p. 1, column 3)
• Year of Pluto collection
  • Letter suggesting the name Pluto (1930)
  • Explanation for the name Pluto (1930)
  • Pluto announcement from Harvard College Observatory (1930)
  • "The Founding of Lowell Observatory" 
  • "Clyde Tombaugh and Planet X," Arizona Highways, May 1994 (p. 51)
  • Easy Field Guide to the Arizona Night Sky