In 2016, Batygin and Brown first outlined in detail how the orbits of six of these objects could be explained by a specific Planet Nine. They predicted this world must have a mass at least 10 ...

Rachel Feltman: For Scientific American’s Science Quickly, I’m Rachel Feltman. Unless you’re really on the low end of our listener age bell curve, chances are you grew up learning about our ...

The newcomer replacing Pluto presently goes by “Planet Nine.” If and when it finally shows up, it will get the honor of a real name, but so far, the evidence for this hypothetical planet is ...

For years, scientists have observed the Solar System’s outer reaches in search of a Planet Nine. While Pluto was demoted to ...

Known as Planet Nine or Planet X, it is a hypothetical planet that has long been rumoured to exist in the outer solar system. Although "several claims to have found an extra planet have been made ...