Why Pluto is not considered a planet?
Pluto was considered the ninth planet in our solar system for many years until 2006 when the International Astronomical Union (IAU) redefined the criteria for what constitutes a planet. As a result, Pluto was reclassified as a "dwarf planet." Here are the reasons why Pluto is not considered a planet:
- Size: Pluto is much smaller than the other eight planets in the solar system. Its size is comparable to that of some moons, such as Ganymede and Titan.
- Orbit: Pluto's orbit is more eccentric and inclined compared to the eight planets. It crosses the orbit of Neptune at times, which is one of the criteria used by the IAU to classify planets.
- Clearing the neighborhood: One of the criteria for a celestial body to be considered a planet is that it must have cleared its orbit of other debris. Pluto shares its orbit with other objects in the Kuiper Belt, so it does not meet this criterion.
- Composition: Pluto is made primarily of ice and rock, unlike the gas giants and terrestrial planets in our solar system. Its composition is more similar to that of other objects in the Kuiper Belt.
- Classification: The IAU created a new category called "dwarf planets" for objects like Pluto that did not meet all the criteria to be classified as a planet. This category includes other objects such as Eris and Haumea.
In conclusion, while Pluto was once considered the ninth planet, it does not meet all the criteria set forth by the IAU for what constitutes a planet. As a result, it is now classified as a dwarf planet.