If you grew up learning that Pluto was a planet, chances are you were sticking to that, no matter what the IAU said. After ...

Although Pluto's orbit was more elongated than the other planets' (and even crossed the orbit of Neptune—not the kind of thing you would expect a decent planet to do), it seemed alone in its ...

Not fulfilling the second criteria, Pluto went from being the ninth planet in our solar system to one of five dwarf planets, with the IAU stating that Pluto is "an important proto-type of a new ...

Pluto was once called the ninth planet, but in 2006, scientists changed its status to a dwarf planet. A planet must clear its orbit of other objects, but Pluto shares its space with many small icy ...

Forbes contributors publish independent expert analyses and insights. Jamie Carter is an award-winning reporter who covers the night sky.

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.

Why was Pluto reclassified as a dwarf planet? One might think that it’s purely a matter of size. Mercury, the smallest of the ...