Clyde Tombaugh discovered Pluto in 1930 at Lowell Observatory in Flagstaff. Here's how Pluto won - and lost - its planetary ...

“New Horizons shattered a major paradigm of planetary science,” says Alan Stern, the mission’s principal investigator. “Pluto turns out to have as much complexity as Mars or Earth, so much so that I ...

Pluto was always in a tough spot when it came to being a planet. Just 1,477 miles across, it's only one-fifth the diameter of Earth. It did have five known moons: Charon, Nix, Hydra, Kerberos and ...

Pluto was reclassified from a planet to a dwarf planet by the International Astronomical Union because it did not meet all three criteria of their updated definition of a planet. According to the ...