海かい王おう星せい外がい天てん体たい

• 小しょう惑わく星せい

  小惑星 (asteroid) generally refers to rocky bodies mainly in the asteroid belt, while 海王星外天体 are icy bodies beyond Neptune.

• 準じゅん惑わく星せい

  準惑星 (dwarf planet) is a classification that includes some 海王星外天体 like Pluto, but not all TNOs are dwarf planets.

Compound of 海王星 (Neptune) + 外 (outside) + 天体 (celestial body), literally 'celestial body outside Neptune's orbit'.