(CNN) – In the ongoing debate over whether or not Pluto is in fact a planet, the scales have tipped back toward yes for the little rock about four-and-a-half billion miles from Earth.
According to a new study of how planets have historically been defined, it should be reclassified as a planet.
In a paper published in the journal Icarus, Philip Metzger, a planetary scientist at the University of Central Florida, argues that the reason Pluto lost its planet status is not valid.
In 2006, the International Astronomical Union (IAU) downgraded Pluto, which is about half the width of the United States, to a dwarf planet.
The IAU defines a planet as having the largest gravitational force in its orbit, which disqualifies Pluto because it is under the influence of Neptune's gravity.
Metzger criticizes IAU's method of classifying what is and isn't a planet.
He reviewed scientific literature from the past 200 years and found only one publication, from 1802, that employed the clearing-orbit requirement to classify planets and he said that publication was based on "since-disproven reasoning."
Metzger said that the definition of a planet should be based on its intrinsic properties, rather than ones that can change, such as the dynamics of a planet's orbit.
"The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be defined on the basis of a concept that nobody uses in their research," Metzger said. "And it would leave out the second-most complex, interesting planet in our solar system."