Percival Lowell was a prominent astronomer of the late 19th and early 20th centuries who believed in the existence of a planet beyond Neptune, which he called “Planet X.” Written by Kevin Schindler. Narration by Dr. Nicholas B. Breyfogle. Video production by Hannah Keller, Dr. Nicholas B. Breyfogle, and Laura Seeger. A transcript is available at https://origins.osu.edu/read/discovering-pluto. This is a production of Origins: Current Events in Historical Perspective at the Goldberg Center in the Department of History at The Ohio State University and the Department of History at Miami University. Be sure to subscribe to our channel to receive updates about our videos and podcasts. For more information about Origins: Current Events in Historical Perspective, please visit origins.osu.edu. Learn More: Pluto and Lowell Observatory: A History of Discovery at Flagstaff. Kevin Schindler & Will Grundy. 2018. The History Press. 192 pages. Discovering Pluto: Exploration at the Edge of the Solar System. Dale Cruikshank & William Sheehan. 2018. University of Arizona Press. 504 pages. The Pluto System After New Horizons. Alan Stern, Jeffrey Moore, William Grundy, Leslie Young, Richard Binzel (editors). 2021. University of Arizona Press. 688 pages. Planets X and Pluto. William Hoyt. 1980. University of Arizona Press. 302 pages. Clyde Tombaugh: Discoverer of Planet Pluto. David Levy. 2007. Sky Publishing. 232 pages.