The Pluto Question main content.

The Pluto Question

Far from the Sun and smaller than Earth’s Moon, Pluto went undiscovered until 1930, when it was hailed as the most distant planet.

Since relegated to the status of “dwarf planet,” it remains one of the more mysterious bodies in the Solar System. Launched in 2006 on a decade-long voyage to Pluto and its moons, the New Horizons mission will help scientists determine whether Pluto is in fact a planet — and how the meaning of that term is evolving as we learn more about objects on the outskirts of the solar system.

Support for the development of Science Topics was generously provided by Sidney and Helaine Lerner, GRACE Communications Foundation.