Search for elusive "Planet Nine" takes surprising twist, astronomers say

It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the edge of our solar system, evading all our efforts to spot it. Some astronomers say the strange, clustered orbits of icy rocks beyond Neptune indicate that something big is out there, which they have dubbed "Planet Nine."

Now, a U.S.-based trio hunting the elusive world has instead stumbled on what appears to be a new dwarf planet in the solar system's outer reaches. And the existence of the new kid on the block could challenge the Planet Nine theory, the researchers have calculated.

Named 2017 OF201, the new object is roughly 430 miles across, according to a preprint study, which has not been peer-reviewed and was published online last week. That makes it three times smaller than Pluto.