Pluto, formerly a planet of our solar system, was discovered in 1930. For a long time, we considered the 9 largest objects in our solar system that rotate around the Sun to be planets. However, over time, powerful telescopes helped us understand our solar system better and we have found many more objects in our solar system, apart from these 9 bodies. This caused confusion over what is planet and what is not. International Astronomical Union (IAU) came up with a definition of planet as a round body that orbits Sun and has cleared the neighborhood of its orbit. While Pluto satisfies the first two conditions (round and orbits the Sun), it is yet to clear its neighborhood. The failure to fully satisfy the criteria caused the IAU to vote out Pluto from the list of planets, on 24 August, 2006.
Pluto constitutes only a very very small portion of the mass of bodies in its orbit. In comparison, Earth has more than a million times the mass of the other bodies in its orbit.
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