Many astronomers contend the ninth rock from the sun never deserved to be a full planet in the first place.
Discovered by Clyde Tombaugh of Arizona's Lowell Observatory, Pluto was classified as a planet because scientists initially believed it was the same size as Earth. It was the only known object in the Kuiper Belt and in 1978, it was found to have a moon - Charon. But in the 1990s, more powerful telescopes revealed numerous bodies similar to Pluto in the neighborhood.
Scientists agree that to be called a planet, a celestial body must be in orbit around a star while not itself being a star. It also must be large enough in mass for its own gravity to pull it into a nearly spherical shape and have cleared the neighborhood around its orbit.
Pluto's reaction to its downgrading has not been recorded.