Why is Pluto classified as a dwarf planet ?

Pluto, the celestial body that once held the title of the ninth planet in our solar system, is now classified as a dwarf planet. This reclassification was established by the International Astronomical Union (IAU) in 2006, based on certain criteria that define what qualifies as a full-fledged planet.

According to the IAU, for an object to be considered a planet, it must meet three standards. Firstly, it must orbit the Sun, which Pluto does. Secondly, it must have a nearly round shape, indicating that it has enough mass for gravity to shape it into a spherical form. Pluto satisfies this criterion as well.

However, it is the third criterion that Pluto fails to meet. In order to be classified as a planet, an object must have cleared its orbit of other debris. This means that any planet should have gravitationally dominated its immediate neighborhood, so that there are no significant objects sharing its orbit or crossing its path. Unfortunately, Pluto shares its orbit with other icy bodies in the Kuiper Belt, therefore it has not cleared its orbit of debris.

As a result, Pluto was reclassified as a dwarf planet, along with other similar-sized objects in the outer solar system. This was a decision made by the scientific community to ensure a consistent classification system for celestial bodies and to distinguish between planets and smaller, less dominant objects.

The reclassification of Pluto sparked some controversy and debate among astronomers and the general public. Many people had grown up learning about nine planets in our solar system, so the demotion of Pluto to dwarf planet status came as a surprise. However, it is important to note that this decision was based on scientific criteria and was aimed at maintaining clarity and consistency in our understanding of the solar system.

In conclusion, Pluto is classified as a dwarf planet because it does not meet the criteria set by the IAU for a full-fledged planet. While it orbits the Sun and has a nearly round shape, it has not cleared its orbit of debris, leading to its reclassification. This decision ensures a standardized classification system and helps us better understand the complexity of our solar system.

Source: International Astronomical Union (IAU)