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Dictionary

Words, grammatical forms and meanings linked to the ontology.

Planet X en · PROPN

Pronunciation

  • /ˈplænɪt ɛks/

Etymology

X represents an unknown as opposed to the Roman numeral for 10 (initially, Planet X would have been the ninth planet).

Meanings

  1. A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)
  2. (obsolete) A theoretical planet responsible for reported gravitational perturbations of Neptune's orbit. (This was initially believed to be Pluto. The reported perturbations were an error.)
  3. (obsolete) A theoretical planet responsible for observed gravitational perturbations of Uranus' orbit. (This planet was discovered and is now known as Neptune.)

Relateds

Tiamat · Nibiru · Planet Nine

Translations (17)

es planeta X (hypothetical planet) · sl planet X (hypothetical planet) · vi hành tinh X (hypothetical planet) · de Transpluto (hypothetical planet) · de Planet X (hypothetical planet) · fr planète X (hypothetical planet) · sv planeten X (hypothetical planet) · mt pjaneta X (hypothetical planet) · yue X行星 (hypothetical planet) · cmn X行星 (hypothetical planet) · ru Плане́та Икс (hypothetical planet) · it pianeta X (hypothetical planet) · fi planeetta X (hypothetical planet) · pt Planeta X (hypothetical planet) · ru Плане́та Х (hypothetical planet) · nl planeet X (hypothetical planet) · ja 惑星Ｘ (hypothetical planet)