Question

1. why is pluto not considered a planet?

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Explanation:

To be a planet, an object must: 1) Orbit the Sun, 2) Be spherical (hydrostatic equilibrium), 3) Clear its orbital neighborhood. Pluto fails the third condition as its orbit overlaps with Neptune - like objects (Kuiper Belt) and it shares its orbital region with other large bodies. Also, the IAU redefined "planet" in 2006, classifying Pluto as a "dwarf planet" since it doesn't dominate its orbit.

Answer:

Pluto is not considered a planet because it does not meet the International Astronomical Union's (IAU) definition of a planet. Specifically, it fails to "clear its orbital neighborhood" (it shares its orbital region with other large celestial bodies like those in the Kuiper Belt) and is now classified as a dwarf planet.