Dwarf planet
From Tardis Wiki, the free Doctor Who reference
Dwarf planets were celestial bodies similar to actual planets, which were nevertheless not considered to fall under the definition of a planet.
Dwarf planets in the Sol system included Eris, Ceres and Pluto. (AUDIO: The Bounty of Ceres)
Although Pluto was not considered to be a planet anymore by Steven Taylor's times (AUDIO: The Anachronauts), some still called it a planet at a much later point in time. (TV: The Sun Makers)
