In 2006 scientists and space enthusiasts were baffled by the International Astronomical Union's (IAU) decision to demote Pluto to a dwarf planet. Today, in a recent study, scientists are demanding that the IAU rescind its earlier decision and establish Pluto and the Moon as planets. These scientists claim that the earlier decision was based on folklore and astrology.
Why isn't Pluto a Planet Anymore?
According to the Library of Congress, in August of 2006, the International Astronomical Union downgraded Pluto to dwarf planet status since the celestial body failed to meet the three criteria defined by the IAU in defining full-sized planets.
A dwarf planet is defined as a celestial body in the direct orbit of the Solar System's Sun that is massive enough that its shape is controlled primarily by gravitational forces. The IAU has three criteria for full-sized planets:
The celestial body is orbiting around the Sun
It should have sufficient mass to assume hydrostatic equilibrium or roundness
And that it has "cleared the neighborhood" around the celestial body's orbit.
Pluto met two of three criteria, only losing out because of the third.
Scientists Urge IAU to Reinstate Pluto and Add the Moon as New Planet
The IAU's 2006 decision studied how the planet's definition changed since Galileo's time. According to the union, a planet has to be the biggest gravitational force in its orbit. In Pluto's case, however, Neptune's gravitational forces influence it. Wherein Pluto shares the orbit along with other frozen gases and numerous objects in the Kuiper belt.
However, authors of a recent study published in the journal Icarus, titled "Moons are planets: Scientific usefulness versus cultural teleology in the taxonomy of planetary science," claimed that the definition by the IAU was rushed before it was able to sort out vital issues. So, the organization should rescind its decision and reinstate Pluto as one of the planets in the solar system.
According to the authors, a much better definition for full-bodied planets should be based on whether the celestial object has ever been geologically active. Although scientists acknowledge that this definition would include the Moon and several asteroids, it would potentially mean several hundreds of planets in the Solar System.
Under the new proposed definition, all moons in the Solar System would be classified as planets. Stating that the idea that moons aren't planets has origins in 1800s astrology and teleology, reports DailyMail.
Charlene Detelich, the author of the study and a geologist at Johns Hopkins University, explains that the term planet considers round icy moons to be included for her, her colleagues, and most scientists. They all have active geologic processes driven by various internal processes, much like any work with enough mass that reaches hydrostatic equilibrium.
She adds that it is more useful for a geologist to divide planets by their intrinsic characteristics than their orbital dynamics. Detelich added that when the 2006 IAU decision was announced, her 10-year-old self was first learning about planets and has since been bothered by the argument of preserving the eight-planet Solar System model.
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