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

There's a new object in the distant reaches of our solar system, and it might just offer clues to a long-standing cosmic mystery. Astronomers have cataloged a frozen minor planet called 2017 OF201, ...

Our solar system is a smashing success. A new study suggests that from its earliest period—even before the last of its ...

Astrophysicist and author Neil deGrasse Tyson explains the theory behind the growing evidence about a possible hidden planet in the Kuiper Belt beyond Neptune.