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

Scientists hunting for the hypothetical Planet Nine have discovered a potential new dwarf planet, 2017 OF201, in the outer ...

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

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

In 2006, the International Astronomical Union stopped classifying Pluto as our solar system’s ninth planet and demoted its ...

U.S. astronomers hunting for "Planet Nine" have instead stumbled on what appears to be a new dwarf planet in the solar system ...

A new dwarf planet discovery in the outer solar system is challenging the long-standing theory of a hidden giant planet ...

A US-based trio hunting this elusive world has stumbled on what appears to be a new dwarf planet in the solar system's outer ...

For decades, our solar system was thought to have nine planets, with Pluto considered the smallest and farthest. But in 2006, ...