Only confused journalists call it "Planet Nine." Its name will always be Planet X, at least until it's found and named after an ancient Indonesian sea serpent or something.

Researchers searching decades-old infrared observations have identified a faint object that appears to have moved across the sky between two surveys taken 23 years apart. Its brightness and slow motion fit what the team expected from a large planet hundreds of times farther from the Sun than Earth.

Planet 9 or Plan 9?