• JTG
  • Helping Hand
1. It was discovered that asteroid Xena (now known as dwarf planet Xena) is bigger than Pluto.

2. It was a planet until astronomers realized that it's too small because of the said asteroid and renamed it from the "smallest planet" to "dwarf planet".

3. Pluto did not meet the 3 criterias or requirements for a full-size planet.