noun
dwarf planet
Astronomical term for a celestial body that orbits the sun and is massive enough to be rounded by its own gravity, but has not cleared its neighboring region of planetesimals. Used in modern astronomy since the 2006 IAU definition.
冥王星は2006年に準惑星に分類された。
Pluto was classified as a dwarf planet in 2006.
太陽系には現在5つの準惑星が確認されている。
There are currently five recognized dwarf planets in the solar system.