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 last and least of them. An icy dwarf only half the size of the United States, it was on average 3.7 billion miles from the sun. It also has a decidedly strange orbit that was highly ...

The International Astronomical Union reclassified Pluto as a dwarf planet because it does not clear its orbit of other debris. Pluto was the little planet that could — until it couldn’t.