Pluto has been demoted because it does not dominate its neighbourhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.
In addition, bodies that dominate their neighbourhoods, "sweep up" asteroids, comets, and other debris, clearing a path along their orbits. By contrast, Pluto's orbit is somewhat untidy.
neighbourhood around its orbit.
Pluto has been demoted because it does not dominate its neighbourhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.
In addition, bodies that dominate their neighbourhoods, "sweep up" asteroids, comets, and other debris, clearing a path along their orbits. By contrast, Pluto's orbit is somewhat untidy.
Poseidon
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JesusChristMan say: pluto is just a star,the earth is flat!
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Bill say: Scientists have discovered more objects in the outer solar system that would have to be classified as planets if Pluto was a planet.
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Donut Tim say: In 2006 an International Astronomical Union (IAU) resolution created an official definition for the term "planet" in our solar system. Before that time there was no official definition and so many objects were being discovered that a classification system was needed. According to this resolution, there are three main conditions for an object to be considered a 'planet':
~ The object must be in orbit around the Sun.
~ The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
~ It must have cleared the neighborhood around its orbit.
Pluto fails to meet the third condition, since its mass was only 0.07 times that of the mass of the other objects in its orbit (Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit).
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