Facts about Dwarf planet definition
- 08
Astronomers estimate approximately 200 dwarf planet candidates exist in the Kuiper Belt and scattered disk regions, vastly outnumbering the five currently recognized members of this classification.
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Objects in the dwarf planet category must be large enough to achieve a nearly round shape through their own gravity, a requirement that excludes thousands of smaller irregular asteroids from this classification.
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Hydrostatic equilibrium, the balance between gravity and internal pressure that defines dwarf planets, requires objects to achieve sufficient mass around 5 × 10^20 kilograms to become rounded by their own gravity.
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Over 150 additional dwarf planet candidates exist beyond Neptune in the Kuiper Belt, though only five have received official IAU recognition due to incomplete orbital data.
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Eris, discovered in 2005, is actually more massive than Pluto despite being smaller in diameter, which challenged the traditional planet definition and helped prompt the dwarf planet classification system.
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Five dwarf planets in our solar system have been officially recognized by the IAU: Pluto, Eris, Haumea, Makemake, and Ceres, with Ceres being the only one located in the asteroid belt.
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Pluto was reclassified from planet to dwarf planet in 2006 because it has not cleared its orbital neighborhood of other debris, failing one of the three IAU criteria.
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The International Astronomical Union established the dwarf planet definition in 2006, requiring objects to orbit the sun and be massive enough for hydrostatic equilibrium.