In 2006, Pluto was demoted to a dwarf planet by the IAU. Dwarf planets are celestial bodies in regular orbit around a sun with sufficient mass to be shaped by their own gravity. There are five known dwarf planets, including Ceres, Makemake, Haumea, and Eris. Ceres and Pluto were both classified as dwarf planets in 2006, while Makemake and Haumea received this classification in 2008.
In August 2006, members of the International Astronomical Union (IAU) voted to demote Pluto to dwarf planet status. Planets of this type are celestial bodies that are in regular orbit around a sun and have sufficient mass to be shaped by their own gravity, but are generally smaller than the planet Mercury. Unlike moons, dwarf planets do not orbit inner or outer planets. Along with Pluto, there are four other known dwarf planets in the solar system: Eris, Makemake, Haumea and Ceres.
Learn more about dwarf planets:
Ceres and Pluto are relatively new to dwarf planet status. Ceres was elevated from asteroid or minor planet status to dwarf planet in 2006, the same year Pluto was demoted.
Pluto is tilted on its axis, which affects its orbit. Every 248 Earth years, Pluto slips into Neptune’s orbit and remains within that planet’s orbit for 20 years.
Makemake and Haumea were classified as dwarf planets after Pluto’s reassignment. Makemake was accepted as a dwarf planet on July 11, 2008, and Haumea received this classification on September 17, 2008.
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