Planet Nine

Could another large planet be hiding far beyond Neptune? Some distant small bodies follow unusual orbits, and a planet’s gravity might help explain their arrangement. Planet Nine is that proposed world, not a confirmed discovery.[1] [2]

Can the unseen-planet hypothesis account for distant-body orbits after survey selection is considered, and can direct searches confirm or exclude the allowed planet? A model prediction of a perturber is not a detection.[1] [2]

The orbital clues are debated, partly because surveys find some kinds of orbit more easily than others. Searches have found no confirmed planet. An empty searched patch rules out some locations and brightnesses; it does not cover every place a faint planet could be.[1] [2]

The January 2026 revision reports a bounded null search with field-specific brightness and recovery limits. It uses apparent night-to-night motion from Earth’s changing viewpoint. Its sensitivity and selected sky region leave other possibilities open; completeness is not a posterior probability that the planet does not exist.[1] [2]

The familiar planets may not be the Solar System’s complete inventory. A distant planet would affect how other objects move; even ruling it out would require understanding why their orbits look as they do. The search connects finding a world with explaining the system around it.[1] [2]

Gravitational explanations connect an unseen object to the behavior of visible ones. A convincing answer would clarify how the distant Solar System is organized and whether its orbital patterns require another major body. Testing selection effects is part of that explanation, not merely an obstacle to discovery.[1] [2]