But in recent years, astronomers have proposed that a ninth world, imaginatively nicknamed "Planet Nine," could be hiding ...

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 ...

Speculation swirls as scientists debate if Planet Nine is a celestial body or something darker. Clues emerge from unexplained gravitational anomalies far beyond Neptune. A radical hypothesis ...