Which celestial body is famously cited as the object whose demotion necessitated the finalization of the third IAU planetary criterion regarding orbital dominance?
Answer
Pluto
Pluto serves as the primary, historically significant example illustrating why the third criterion—clearing the neighborhood—was introduced into the IAU definition in 2006. Although Pluto orbits the Sun and is large enough to be nearly round (satisfying the first two criteria), it resides within the Kuiper Belt alongside countless other icy objects. Because Pluto has not gravitationally dominated this region, ejecting or absorbing its neighbors, it failed the test of orbital clearing. This situation necessitates its current classification as a dwarf planet, contrasting sharply with the eight major planets which have overwhelmingly cleared their respective orbits.
Related Questions
What is the third specific criterion an object in our solar system must meet according to the International Astronomical Union (IAU) definition to be classified as a planet?Which celestial body is famously cited as the object whose demotion necessitated the finalization of the third IAU planetary criterion regarding orbital dominance?Why does the strict IAU ruling concerning planetary classification immediately exclude confirmed exoplanets from being labeled as planets?What physical state, related to self-gravity overcoming rigid body forces, is required by the second criterion for an object to be considered a planet under the IAU definition?What ancient Greek word is the term 'planet' derived from, and what descriptive meaning did it convey regarding these celestial bodies?What component is central to the proposed alternative scientific definition of a planet that aims for a more universal classification across the galaxy, independent of our solar system's architecture?What classification category is assigned to a solar system object that successfully orbits the Sun and achieves hydrostatic equilibrium but fails the third criterion regarding its orbital path?In the context of planetary classification debate, what aspect of planetary assessment do many working planetary scientists, especially those studying Pluto, feel the IAU definition focuses on too heavily?When is the three-pronged IAU rule considered the definitive standard for classifying a celestial body, as opposed to a geophysical definition?What does the table summarize about the status of bodies like Earth and Jupiter compared to bodies like Pluto and Ceres following the 2006 IAU decision?According to the Planetary Dominance Analysis, how does Jupiter's mass compare to the combined mass of all other orbiting objects in the solar system?