Pluto's reclassification from being considered the ninth planet to being designated as a "dwarf planet" was not directly related to Neptune intersecting its orbit. The reclassification was primarily based on a reevaluation of the definition of a planet by the International Astronomical Union (IAU) in 2006.
Prior to this redefinition, the term "planet" did not have a clear and specific definition. The discovery of numerous objects in the outer regions of the solar system, similar in size to Pluto, prompted the need for a more precise definition to classify these objects. The IAU's new definition of a planet established three criteria that a celestial body must meet to be classified as a planet:
- It must orbit the Sun.
- It must be spherical in shape, due to its own gravity.
- It must have cleared its orbit of other debris.
While Pluto meets the first two criteria, it fails to meet the third criterion. Its orbit overlaps with that of Neptune, and it shares its region of space, known as the Kuiper Belt, with other similar-sized objects. Therefore, according to the IAU's definition, Pluto was reclassified as a dwarf planet.
The reclassification was a scientific decision made by the IAU to provide a more precise and consistent classification system for objects in the solar system. It was not solely based on Neptune intersecting Pluto's orbit but on the need to establish clear criteria for planetary classification.