Why Is Pluto Not a Planet?

A look into how Pluto got kicked out of the planet club.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker — Taken by New Horizons, 2015

Pluto was previously considered a planet since its discovery in 1930 by Clyde Tombaugh. Pluto had little resistance to its classification as the ninth planet upon its discovery.

This may have been a slight case of confirmation bias since the presence of a “ninth planet” or “planet X” was…