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

He called this hypothetical world "Planet X." "In some ways, Pluto's more of a planet than some of the other established planets, like Mercury." ...

“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 discovered at Lowell Observatory in Flagstaff, Arizona in 1930 and was considered our ninth planet until 2006. The International Astronomical Union reclassified Pluto as a dwarf planet ...

If you answered "Pluto's planethood," your grasp of the astronomical is excellent. Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet. Here's what to know about ...