Pluto
Pluto is a Trans-Neptunian object, the first to be identified in history. It was discovered in 1930 by Clyde Tombaugh.
It was considered as the ninth and last planet, lying beyond Neptune. However, the formal definition of a planet introduced by the International Astronomical Union in 2006 resulted in Pluto losing its status and becoming a dwarf planet.[1] It is very small, rocky, and cold, because it receives little light from the Sun.
It has multiple satellites. Charon is the biggest, about half its size, and the first to be discovered. Two other are Nix and Hydra.
References
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"Eris". NASA Science. 2017-11-15. Archived from the original on 2026-07-04. Retrieved 2026-07-09.
The discovery of Eris help trigger a debate in the scientific community that led to the International Astronomical Union's decision in 2006 to clarify the definition of a planet. Pluto, Eris, and other similar objects are now classified as dwarf planets.