Is Demoted Planet Pluto Making A Comeback?

Ever since astronomer Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona, discovered it on February 18, 1930, we've believed that we live in a solar system with nine planets. Then, in 2006, along came the International Astronomical Union. The group decided Pluto isn't a planet.

It was demoted to a dwarf planet. But the group's definitions sparked lots of debate. On September 18, the Harvard-Smithsonian Center for Astrophysics jumped into the debate: What is a planet? It had some experts discuss the definition of a planet and then let the audience vote. Guess what? They voted that Pluto is a planet.