Editing Solar System (section)

== Dwarf planets ==
{{Main|Dwarf planet}}

Pluto was discovered by American astronomer [[Clyde Tombaugh]] in 1930. It was declared the ninth planet of the Solar System. 

Pluto's planet status changed in 2006, when the [[International Astronomical Union]] (IAU) decided on a definition of the word "planet" for the first time. By this definition, Pluto was not a planet due to its irregular orbit and size. Thus, Pluto lost its planet status. 

Eris was first announced in 2005. It was found to be 27% more massive than Pluto. Pluto did not fit in with the rest of the planets. So, the IAU defined a new category called "dwarf planet", into which Pluto did fit, along with some other small Solar System bodies. These small bodies are sometimes called [[plutino]]s.<ref>{{cite web|title=IAU 2006 General Assembly: Result of the IAU Resolution votes|url=https://www.iau.org/news/pressreleases/detail/iau0603/|url-status=dead|archive-url=https://web.archive.org/web/20140429212224/https://www.iau.org/news/pressreleases/detail/iau0603/|archive-date=2014-04-29|publisher=IAU|accessdate=2018-09-04}}</ref>

There is an unknown number of dwarf planets in the Solar System. As of 2025, these nine small Solar System bodies are often called dwarf planets:
* [[Pluto]]
* [[Ceres (dwarf planet)|Ceres]]
* [[Haumea (dwarf planet)|Haumea]]
* [[Eris (dwarf planet)|Eris]]
* [[Makemake (dwarf planet)|Makemake]]
* [[50000 Quaoar|Quaoar]]
* [[90377 Sedna|Sedna]]
* [[90482 Orcus|Orcus]]
* [[225088 Gonggong|Gonggong]]