Scientist: Pluto Should be Planet, Definition of Planet Is Sloppy

Scientist Philip Metzger of the University of Central Florida has effectively started a dialog that could have Pluto reinstated as a planet. “The IAU (International Astronomical Union) 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.”

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Metzger says Pluto is “more dynamic and alive than Mars” and is the “second-most complex, interesting planet in our solar system” behind the Earth.

According to the IAU, a “planet” is defined as a celestial body that (1) is in orbit around the Sun, (2) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium or nearly round shape and (3) has cleared the neighborhood around its orbit.

“We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it’s functionally useful,” the scientist further explain.

“It’s a sloppy definition. They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.”

The ninth planet from the sun was redesignated a dwarf planet in 2006, citing there were other objects orbiting our sun that were of a similar size to Pluto.

Metzger is proposing that a planet should be defined by whether the body is large enough that its gravity becomes spherical. 

“And that’s not just an arbitrary definition,” Metzger declared, adding that “it turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body.”

Clyde Tombaugh discovered Pluto in 1930.