When categorizing a celestial body as a planet, the International Astronomical Union (IAU) established three criteria in 2006. Understanding these criteria is essential to comprehend why Pluto is not classified as a major planet:
- Firstly, the body must orbit the Sun. This is a basic requirement shared by all planets in our solar system.
- Secondly, it must have sufficient mass for its gravity to form it into a nearly round shape. Gravity's role in shaping these bodies is crucial for maintaining stability and integrity across orbits.
- Lastly, the celestial body must have cleared its neighboring region of other objects. This means it has become gravitationally dominant, with no similar-sized bodies other than its satellites in its vicinity.
Pluto meets the first two criteria but falls short on the third due to the numerous objects in the Kuiper Belt.
Consequently, it has been reclassified as a dwarf planet. Understanding these criteria helps us categorize the diverse objects that populate our cosmic neighborhood, providing a clearer picture of our place in the universe.