First Photograph of Pluto

Date: August 20, 1909 • Location: Williams Bay, United States

Pluto (pictured) was photographed for the first time at the Yerkes Observatory in Williams Bay, Wisconsin, U.S., 21 years before it was officially discovered by Clyde Tombaugh.

Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume by a small margin, but is less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets. Pluto has roughly one-sixth the mass of the Moon and one-third of its volume. Originally considered a planet, its status was changed when astronomers adopted a new definition of the word with new criteria.