Is Planet Nine an undiscovered world?

Scientists have chased a theory for decades…but is it a ghost, a black hole, or a newfound planet?

Is There A HIDDEN Massive PLANET in Our Solar System?

How Many Planets Are There in the Solar System?

Backyard Worlds - Wikipedia

Planet 9 may be closer and easier to find than thought—if it exists

Planet Nine - Wikipedia

The Truth Behind Nibiru, aka Planet X

New Dwarf Planet Found in the Outskirts of the Solar System, Giving Astronomers More Ammunition to Search for Evidence of Planet 9 - Universe Today

Planet

What is Planet Nine The Mysterious Missing Piece in Our Solar System Puzzle - Pediafor

Why an Undiscovered Planet in Our Solar System Is Unlikely

On the hunt for Planet Nine - The Boston Globe