Planet X

English

Etymology

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

Pronunciation

• IPA^(key): /ˈplænɪt ɛks/

Proper noun

Planet X

1. (astronomy) 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. (astronomy, 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. (astronomy, obsolete) A theoretical planet responsible for observed gravitational perturbations of Uranus' orbit. (This planet was discovered and is now known as Neptune.)

Translations

hypothetical planet

• Chinese:

  Cantonese: X行星 (iks¹ hang⁴ sing¹, iks¹ haang⁴ sing¹)

  Mandarin: X行星 (X xíngxīng)

• Dutch: planeet X f
• Finnish: planeetta X
• French: planète X f
• German: Transpluto m, Planet X m
• Italian: pianeta X m
• Japanese: 惑星Ｘ (wakusei X)
• Maltese: pjaneta X
• Portuguese: Planeta X m
• Russian: Плане́та Х f (Planéta X), Плане́та Икс f (Planéta Iks)
• Slovene: planet X m
• Spanish: planeta X m
• Swedish: planeten X c
• Vietnamese: hành tinh X

See also

• Nibiru
• Tiamat

Anagrams

• explant