Pluto and the more distant dwarf planets fail to meet this criterion. If Pluto were to keep its planetary status, those dwarf planets would also need to be classified planets. While astronomers ...

Once the quirky underdog of our solar system, Pluto held planetary status until 2006, when it got a cosmic demotion that still stings space fans. Discovered in 1930, Pluto was the ninth planet for ...

For the dwarf planet candidate, one trip around the sun takes over 24,000 years. Its orbit challenges a proposed path for a hypothetical Planet Nine.

Astronomers find evidence of a possible ninth planet beyond Neptune, reigniting the debate about the formation of the Solar ...

It’s a sloppy definition,” he says. His stance is that the one sticking point for those who wanted to strip Pluto of its planetary status — the “clear” orbit requirement — isn’t ...

The first observations of Pluto by NASA’s James Webb Space Telescope (JWST) reveal dramatic phenomena on its surface, like ...

Pluto has never been much of a planet — small, wired orbit, not much atmosphere — and questions about its status have been raised periodically since its discovery 76 years ago. This week ...

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

Learn about the recently discovered trans-Neptunian object that may eventually join Pluto as a dwarf planet, found at the ...

It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the ...

It is an evocative idea: a huge and mysterious planet is lurking in the darkness at the edge of our solar system, evading all ...