So things stood for 65 years. 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 ...

The strange blend of surface chemistry on Nix and Hydra raises big question about the evolution of the Pluto system.

When the International Astronomical Union (IAU) demoted Pluto from a planet to a dwarf planet in 2006, it surprised a lot of people, including some scientists. Even many years later, some ...

As the planet farthest from the sun, Pluto’s orbit is an arduously long one, with the planet changing signs once every 12 to ...

Sunny stuff, it ain’t. Petit but potent, Pluto was discovered in 1930. Pluto’s orbit is arduously long, with the planet changing signs once every twelve to thirty years. As an outer planet ...

In the time Pluto was found, classified as a planet and reclassified as a dwarf planet, it has not completed one orbit. One year on the distant ice planet is 248 Earth years, and one day is 153 ...

And 3. A planet has "cleared its neighborhood" of smaller bodies within its orbit. Pluto meets the requirements for the first two categories, astronomers reasoned, but it has not cleared its orbit ...

(See what scientists say about Pluto’s status as a planet.) As early as the 1840s, a tricky calculus foretold the existence of a planet beyond the orbit of Neptune. Calculations based on Neptune ...