SIZE doesn’t matter, according to scientists who think petite Pluto should be called a planet once more.
The definition which demoted Pluto is “sloppy” according to University of Central Florida planetary scientist Philip Metzger.
In 2006 the International Astronomical Union defined a planet as an object that:
• Orbits The Sun
• Has enough mass to be round
• Is not a satellite (moon) of another object
• Has cleared debris from the area around its orbit (i.e. is the largest gravitational field in its orbit)
“It’s more dynamic and alive than Mars”
Planetary scientist Philip Metzger
This last criteria saw Pluto be reclassified to a dwarf planet because it is circled by objects which together have a greater mass.
But pro-Pluto expert Metzger discovered that scientists studying our solar system over the past 200 years haven’t used clearing as a definition — because it’s useless.
“The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a 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.”
“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.
“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,” he told Astromart.
Many debris and satellites orbit Earth, for instance.
Metzler believes planets should be defined simply as an object with enough mass, and therefore gravity, to be round.
He said that this definition is important because when something in space is big enough to be spherical it sets-off “active geology”.
For example, Pluto has an underground ocean, a complex atmosphere, moons, possible lakes, and organic compounds (the building blocks of all life).
“It’s more dynamic and alive than Mars,” said Metzger. “The only planet that has more complex geology is the Earth.”
The Reclassification of Asteroids from Planets to Non-Planets by Philip T. Metzger, Mark V. Sykes, Alan Stern, and Kirby Runyon was published in the journal Icarus on August 29.