Pluto's status as a planet has been a subject of debate and controversy in the scientific community. In 2006, the International Astronomical Union (IAU), the organization responsible for classifying celestial bodies, established a formal definition of a planet. According to this definition, a planet must meet three criteria:
- It must orbit the Sun.
- It must be spherical in shape, or nearly so, due to its own gravity.
- It must have cleared its orbit of other debris.
Pluto meets the first two criteria, but it fails to fulfill the third criterion. Pluto's orbit overlaps with the orbit of Neptune, and it shares its region of space, known as the Kuiper Belt, with other objects. This means that Pluto has not cleared its orbit of debris, unlike the eight planets recognized by the IAU.
Based on this definition, the IAU reclassified Pluto as a "dwarf planet" rather than a full-fledged planet. Dwarf planets are celestial bodies that meet the first two criteria but do not satisfy the third criterion. This decision was made to provide a clear and consistent classification system for celestial objects.
The reclassification of Pluto sparked some controversy and differing opinions among scientists and the public. Some people still consider Pluto a planet based on other criteria or sentimental reasons. However, according to the IAU's definition, Pluto is now classified as a dwarf planet.