Question

Why was Pluto reclassified as a dwarf planet? (A) Pluto has not cleared its neighboring region of other objects. (B) Pluto's orbit is not on a plane with the planets. (C) Pluto is in direct orbit with the Sun. (D) Pluto has not attained hydrostatic equilibrium.

Answer 1

Pluto was reclassified as a dwarf planet because, while it orbits the Sun and has enough mass to be nearly round, it has not cleared its orbital neighborhood of other objects, thus failing to meet one of the three criteria set by the International Astronomical Union.

Step-by-step explanation:

The reclassification of Pluto as a dwarf planet followed the establishment of three criteria by the International Astronomical Union in 2006, which a celestial body must meet to be considered a 'planet':

1. It must be in orbit around the Sun,
2. It must have sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3. It must have cleared the neighborhood around its orbit.

Pluto satisfies the first two requirements but does not meet the third because it shares its orbital zone with other objects in the Kuiper belt. As a result, Pluto was reclassified as a dwarf planet, which remains in orbit around the Sun and has adequate mass for hydrostatic equilibrium but does not clear its orbital neighborhood.