Ninth planet (disambiguation)

Ninth planet is a concept relating to planets beyond Neptune after the reclassification of Pluto.

Ninth planet or Planet Nine may also refer to:

• Planet Nine, a hypothetical large ninth planet in the Solar System
• Pluto, the ninth planet from its discovery in 1930 until its reclassification as a dwarf planet in 2006
• Neptune, the ninth-closest planet to the Sun from 1979 to 1999 while Pluto was closer to the Sun. Also the ninth planet if Ceres is counted.
• 2 Pallas, an asteroid, the ninth planet in chronological discovery order from 1802 until its reclassification as a minor planet in the 1850s
• Jupiter, considered the ninth-closest planet to the Sun from 1807 to 1845 as a result of the discovery of minor planets

Non-astronomical definitions

• Planet 9 (record label)
• The Secret of the Ninth Planet, a science fiction novel by Donald A. Wollheim