Almost 10 years ago, a NASA spacecraft was able to take several photos of Pluto, known for decades as a planet before it was ...

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

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is ...

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 ...

Nevertheless, because it orbited the Sun like a planet, it was classified as a planet and named Pluto, after the god of outer darkness in Roman mythology. So things stood for 65 years. Although ...

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 ...

And if you are still a Pluto-is-a-planet holdout, like we were, [Michael]’s argument that counting all the Trans-Neptunian Objects would lead to madness is pretty convincing. It sure would make ...

This story appears in the July 2015 issue of National Geographic magazine. Small, cold, and absurdly far away, Pluto has always been selfish with its secrets. Since its discovery in 1930, the ...