It saw the discovery of dwarf planet Eris and how those very observations led to a new way to describe the Solar System and heralded the eventual change of Pluto’s planetary status. On that ...

The controversy endures over Pluto's true status, but the solar system underdog continues to capture hearts across the globe. Clyde Tombaugh didn't set out to discover Pluto when he sent his ...

Ceres is a dwarf planet in the asteroid belt between Mars and Jupiter. It's the largest object in the asteroid belt and the closest dwarf planet to Earth.

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 ...

From there, it broke free and entered its screwy orbit. Allow little Pluto to keep its planetary status and you would have to confer the same honor on Eris, a Kuiper Belt object of about the same size ...

(Correction: An earlier version of this story misstated how far Pluto is from the sun. The correct number is 3.7 billion miles.) What was discovered in Flagstaff, Arizona, and killed off in Prague?

Pluto was discovered at Lowell Observatory in Flagstaff, Arizona in 1930 and was considered our ninth planet until 2006. The International Astronomical Union reclassified Pluto as a dwarf planet ...

Pluto the planet came first ... Haumea, Makemake, and Eris). Astronomer Mike Brown, discoverer of most of those dwarf planets, argues more than 700 other objects could be considered planets ...