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Why was Pluto reclassified as a dwarf planet in 2006?

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Illustration showing the eight planets of the solar system in order from the Sun-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune-depicted to scale by size, with labeled diameters in miles and kilometers. The Sun is partially visible on the left for comparison. — Solar system The planets (in comparative size) in order of distance from the Sun.

In 2006, the International Astronomical Union (IAU) reclassified Pluto as a dwarf planet because it failed to meet the newly established criteria for a planet within our solar system.12

To be considered a planet, a celestial body must satisfy three conditions:
* It must orbit the Sun.
* It must be large enough for its own gravity to pull it into a spherical shape.
* It must have "cleared the neighbourhood" around its orbit, meaning its mass is sufficient to have gravitationally removed other debris from its orbital path.23

While Pluto meets the first two criteria, it fails the third. Pluto resides within the Kuiper belt, a region populated by numerous icy and rocky bodies. Because Pluto has not cleared this neighborhood, it is categorized as a dwarf planet rather than a major planet. This decision reflected a growing scientific consensus that Pluto is one of many large objects in the Kuiper belt, rather than a unique planetary body.234