When astronomers found a large world farther out than Pluto, it became one of the final nails in the coffin of our ninth ...

The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

(The object is now called Eris.) Over a thousand objects ... a dozen of the biggest ones to the list of planets. The region where these bodies orbit is now called the Kuiper (pronounced Chi ...

Pluto isn't alone—it's part of the Kuiper Belt with possibly hundreds of other planet-sized objects. Because Pluto hasn't achieved gravitational dominance in its region, the International Astronomical ...

For decades, Pluto was celebrated as the ninth planet of our solar system. However, in 2006, the International Astronomical ...

is a disc-shaped region beyond the orbit of Neptune’s in the outer solar system—50 Earth-sun distances—that’s home to dwarf planets like Pluto, Makemake and Eris. It’s also thought to be ...

So now its rotation axis is pointed almost in the same direction as its orbit around the sun ... Brown discovered the dwarf planet Eris, a breakthrough that helped prompt a new definition of ...

Each ring represents an object's orbit, and the mess of ... and the randomness of the dwarf planets is quite apparent." Brown is the person who discovered Eris, a 10th solar system object that's ...