ASTRONOMY AND SPACE EXPLORATION

Viewpoint: Yes, Pluto's status as a planet has been continually defended by the International Astronomical Union. Although its size and elliptical orbit do differ from those of the solar system's other planets, these criteria are arbitrary traits that do not discount its status as a planet.

Viewpoint: No, Pluto has more in common with the comets and asteroids discovered in the Kuiper Belt during the 1990s.

The controversy surrounding the planetary designation of Pluto sounds deceptively simple. While Pluto was identified as a planet upon its discovery in 1930, recent refinements in the taxonomy of orbital bodies have raised questions about whether Pluto is "really" a planet, or one of the smaller, more numerous objects beyond Neptune that orbit our Sun. Part of the controversy is essentially semantic: there is no rigid, formal definition of "planet" that either includes...