After studying thousands of computer simulations of the solar system, researchers at Rice University and the Planetary Science Institute think there’s a 40% chance an elusive “Planet Nine” or “Planet ...

There have been questions about a mysterious ninth planet in our solar system for nearly a decade. Pluto was unseated as number nine in 2006. Now, a group of international researchers say they may ...

A recent research paper suggests that a planet may exist far beyond Neptune — less than 20 years after the previous ninth planet, Pluto, was demoted. That research paper, accepted last month for ...

Mike Brown is convinced that beyond Neptune, at the far reaches of our solar system, there's an unseen giant planet. "This is the 5th largest planet in our solar system, lurking out there, waiting to ...

In the cold, distant reaches of the Solar System, far beyond Pluto, astronomers have just identified what could be a new dwarf planet. It's called 2017 OF 201, a rock that appears to be some 700 ...

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is hidden in our solar... If Planet Nine is out there, this telescope might ...