Defining the Criteria for Planetary Classification
The concept of a planet is defined by several key characteristics that differentiate it from other celestial bodies in the Solar System. In 2006, the International Astronomical Union (IAU) established three primary criteria that must be met for a body to be considered a planet. First, the body must orbit the Sun. Second, the body must have sufficient mass for gravity to give it a nearly spherical shape (Malhotra & Ito, 2022). Third, the body must “clear its orbit” of other objects.
Pluto’s Features and Their Alignment with Planetary Standards
Pluto was discovered in 1930 and was considered the ninth planet of the solar system until 2006. Thus, Pluto does orbit the Sun, and its orbital period is about 248 Earth years. This satisfies the first criterion. Furthermore, Pluto has a nearly spherical shape due to the force of its gravity, meeting the second criterion.
However, Pluto does not satisfy the third criterion for being a planet (Malhotra & Ito, 2022). Pluto is located in the Kuiper belt, a region of numerous objects, including icy bodies and meteorites. Clearing its orbit implies that a planet must be the dominant object in its orbit and gravitationally interact with other bodies in such a way as to remove or stabilize them in its orbit. Thus, since Pluto does not meet the third criterion, it was reclassified by the IAU in 2006 as a “dwarf planet” rather than a full-fledged solar system planet.
The Debate and Scientific Reasons Behind Pluto’s Reclassification
The reclassification of Pluto’s status was prompted by the discovery of other similar trans-Neptunian objects, such as Eris and Haumea, which raised discussions on what should be considered a planet. If Pluto retains its status as a planet, it can lead to many new planets in the Solar System based solely on their size and orbital characteristics (Volk & Malhotra, 2022). This aspect can provoke the reevaluation of planet classification and complicate the understanding and study of the Solar System. Thus, there was a need for more precise definitions and criteria for planet classification. The reclassification of Pluto and the introduction of the category of a dwarf planet helped scientists systematize the knowledge of the Solar System and develop more accurate and agreed-upon methods of research.
References
Malhotra, R., & Ito, T. (2022). Pluto near the edge of chaos. Proceedings of the National Academy of Sciences, 119(15), e2118692119. Web.
Volk, K., & Malhotra, R. (2022). Orbital dynamics landscape near the most distant known trans-Neptunian objects. The Astrophysical Journal, 937(2), 119. Web.