Planet Again? Pluto, Most Moons Count Under Proposed Definition
By Nola Taylor Redd, Space.com Contributor
THE WOODLANDS, Texas — There's new hope for people who still believe that Pluto is a planet more than a decade after the International Astronomical Union (IAU) reclassified the object as a dwarf planet.
A group of planetary scientists is making the case that the definition for a planet should rely more on what an object is than where it is. Pluto's demotion came largely because the world fails to clear its orbit of other large objects (most notably, Neptune). But the proposed geophysical definition focuses on the physical properties of a body rather than the characteristics of its orbit, and would also include objects such as the dwarf planet Ceres and Jupiter's moon Europa.
"The [current] IAU definition [of a planet] is primarily concerned with gravitational perturbations and orbits," Kirby Runyon, a planetary scientist graduate student at Johns Hopkins University told Space.com. "Those aren't what planetary scientists study." [Destination Pluto: NASA's New Horizons Mission in Pictures]