For many years, Pluto was considered the ninth planet in our solar system, but in 2006, the International Astronomical Union (IAU) declared that Pluto is no longer a planet.
This decision was met with mixed reactions, with some people still considering Pluto a planet while others accept the IAU’s decision. So, what led to this decision? In this article, we will explore the reasons why Pluto is no longer a planet based on science.
Criteria to Earn the Name of Planet
Before we dive into the reasons why Pluto is no longer a planet based on science, it is essential to understand the criteria to earn the name of a planet. According to the IAU, a celestial body must meet three criteria to be classified as a planet.
Firstly, it must orbit around the sun. Secondly, it must be massive enough to have a nearly spherical shape, which is known as hydrostatic equilibrium. Lastly, it must have cleared its orbit of other debris, such as asteroids or comets.
Why Pluto is Not a Planet Anymore
Pluto was considered the ninth planet in our solar system until 2006 when it was no longer classified as such. The reasons why Pluto is no longer a planet based on science was due to a review of the criteria for classifying celestial bodies as planets, prompted by the discovery of Eris in 2005.
Eris, a celestial body similar in size to Pluto, highlighted the need for a new classification of celestial bodies, leading to the introduction of the “dwarf planet” classification.
Pluto did not meet the criteria to be classified as a planet because it did not meet the third criterion of clearing its orbit of debris.
The Kuiper Belt, where Pluto orbits, is an area in our solar system filled with icy debris. This means that Pluto shares its orbit with other celestial bodies, and it has not cleared its orbit of debris as required to be considered a planet.
Therefore, the reason why Pluto is not a planet anymore is that it did not meet the criteria set by the International Astronomical Union (IAU) for a celestial body to be classified as a planet.
Specifically, it did not clear its orbit of debris, which led to its reclassification as a dwarf planet. This reclassification expanded our understanding of the variety of celestial bodies that exist beyond the eight planets in our solar system.
Reasons Why Pluto is No Longer a Planet Based on Science
- Size
One of the reasons why Pluto is no longer a planet based on science is its size. Pluto is much smaller compared to the eight planets in our solar system, which means that it does not have enough gravity to pull itself into a nearly spherical shape.
According to the International Astronomical Union (IAU), a planet must be massive enough to have a nearly spherical shape. However, Pluto’s size does not meet this criterion.
Its small size also means that it cannot exert enough gravitational force to clear its orbit of debris, which is the third criterion to be classified as a planet. Therefore, the IAU decided to reclassify Pluto as a dwarf planet.
- Orbit
Pluto’s orbit is not circular like the eight planets in our solar system, but rather it is elliptical. Pluto’s orbit also takes it outside the plane of the solar system, which means it does not follow the same pattern as the eight planets in our solar system.
The elliptical orbit of Pluto is highly elongated, and its distance from the sun varies greatly throughout its orbit. At its closest point, Pluto is about 4.4 billion km from the sun, while at its furthest point, it is about 7.4 billion km away.
- Composition
Pluto’s composition is different from the eight planets in our solar system. It is primarily made up of ice and rock, which is different from the gas giants and rocky planets in our solar system. Pluto’s composition is more similar to that of other celestial bodies in the Kuiper Belt.
The Kuiper Belt is a region beyond Neptune that contains small icy objects, including dwarf planets. The discovery of Pluto led to the identification of the Kuiper Belt, and the study of the region has expanded our understanding of the outer solar system.
- Moons
Pluto has five known moons, which is unusual for a planet. The largest of these moons, Charon, is about half the size of Pluto and is sometimes considered a binary system with Pluto. The other four moons are much smaller and were discovered in 2005 and 2011.
The presence of these moons also contributes to Pluto’s inability to meet the third criterion to be classified as a planet, as they add to the debris in its orbit.
Dwarf Planet
One of the main reasons why Pluto is no longer a planet based on science is that it is now classified as a dwarf planet. A dwarf planet is a celestial body that meets the first two criteria to be classified as a planet but has not cleared its orbit of debris.
This means that Pluto is not alone in its classification as there are other celestial bodies such as Ceres, Haumea, Makemake, and Eris that are also classified as dwarf planets. The classification of dwarf planets has expanded our understanding of the outer solar system and the variety of celestial bodies that exist beyond the eight planets.
Conclusion
The criteria set by the IAU provides the reasons why Pluto is no longer a planet based on science. Pluto’s reclassification as a dwarf planet was due to its inability to meet the third criterion of clearing its orbit of debris.
It is important to note that while some people may still consider Pluto a planet, the scientific classification of celestial bodies is crucial for our understanding of the universe. The study of dwarf planets and other celestial bodies in the Kuiper Belt has greatly expanded our knowledge of the outer solar system and the variety of celestial bodies that exist beyond the eight planets.