"Not only did a planet have to be a ball, but it also had to be a bully." ... What: Gerard van Belle discusses the 2006 vote of the International Astronomical Union to label Pluto a dwarf planet.

How many dwarf planets are there in our solar system? The recent discovery of 2017 OF201 makes the tally anywhere between ...

Sedna will make its closest approach to the Sun in 2076, giving us a rare opportunity to visit the planetoid before it drifts ...

Its demotion in 2006 from 9th planet in the solar system to dwarf planet lives in infamy, though Arizona Gov. Katie Hobbs apparently just signed a law making Pluto the official state planet ...

When NASA's New Horizons spacecraft flew past Pluto in 2015, it shattered the notion that the dwarf planet was a dormant ball of ice, instead revealing it to be rich with icy plains and jagged ...

A team of astronomers believe they may have discovered a new dwarf planet—just like Pluto—on the edge of our solar system. The object—which orbits out beyond Neptune—has been named "2017 OF201" by the ...

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.

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory ...

Whatever we call it, Ceres is a ball of rock and ice with a diameter of 592 miles (953 kilometers). ... Ceres has some similarities with the other dwarf planets, such as Pluto and Eris.