It has captured the imagination of astronomers and sci-fi fans alike, and could turn out to be a real rogue world.
And now researchers believe they may have narrowed down the search for the elusive Planet Nine.
Astronomers are investigating four unknown objects that could be candidates for a new planet in our solar system.
A team of astronomers from the Australian National University (ANU) is investigating the four unknown objects, following the launch of their planetary search on BBC’s Stargazing Live, presented by Professor Brian Cox, and Dara O’Briain.
They said they will reveal more details about the mysterious objects once they have investigated them