A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...

Could a lonely planet wander aimlessly through the restless galaxy change the subtle dance of gravity within our solar system ...

Astronomers are investigating a potential hidden planet, dubbed Planet Y, far beyond Neptune. Its gravitational pull is ...

A new study has proposed the existence of Planet Y, an alternative Planet Nine candidate that is smaller and closer to Earth ...

Astronomers have discovered fresh evidence suggesting the possible existence of an unseen planet in the far reaches of our solar system.

While Planet Y has been not yet been directly observed, unexpected inclinations found in the orbits of roughly 50 distant ...

A low-density, puffy planet orbiting relatively far from a young star in a nearly perpendicular orbit. What's going on?

(CNN) — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have ...

The simulation of the Solar System that came the closest to the observation was the presence of a small planet, between the ...

A strange tilt in the outer reaches of the Kuiper Belt has scientists wondering if the solar system is hiding a potential ...