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

In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet because it doesn't meet all the criteria for full planet status. Pluto was discovered 95 years ago on Feb. 18 ...

Pluto fails the third criterion because its orbit overlaps with objects in the Kuiper Belt, a region of icy bodies beyond Neptune. So, a new class of celestial object — the dwarf planet — came ...

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 ...

“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 ...

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.