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What is the difference between a planetesimal and a dwarf planet?

Robert Anton, Santa Magarita, California
The term "planetesimal" refers to small bodies that orbited the Sun prior to the planets' formation. In 2006, the International Astronomical Union (IAU) ruled that a "dwarf planet" is a nearly spherical celestial body orbiting the Sun that has not cleared its orbital path of debris, as have the traditional planets.

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