The small world was found during a search for the hypothetical Planet Nine, and astronomers say the next time it will reach ...

As it orbits the sun once every 25,000 years, the celestial body 2017 OF201 travels beyond the Kuiper Belt into a region ...

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

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 reaches.

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