Perhaps after “climate change,” the biggest scientific controversy in recent times centered on the status of Pluto within our solar system.

The astronomical body was demoted 12 years ago after a group of elite scientists decided to apply new rules to define “planets”.

In 2006, the International Astronomical Union [IAU], a global group of astronomy experts, established a definition of a planet that required it to “clear” its orbit, or in other words, be the largest gravitational force in its orbit.

Since Neptune’s gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status.However, in a new study published online Wednesday in the journal Icarus, UCF planetary scientist Philip Metzger, who is with the university’s Florida Space Institute, reported that this standard for classifying planets is not supported in the research literature.

The scientists supporting this reclassification included astrophysicist and author Dr. Neil deGrasse Tyson.

Many scientists, myself included, thought the decision was hasty and ill-conceived. Now, a group of scientists argue in a new paper that the definition of a planet that the IAU used to downgrade Pluto’s status has been inconsistently applied . . . and not just in recent decades but over the past 200 years.

“What we’re doing is fact-checking,” said Philip Metzger, a planetary scientist at the University of Central Florida and the lead author of the paper, which was published online Sept. 5 in the journal Icarus. “There are 120 examples I found of scientists in the recent published literature violating the IAU definition, calling something a planet even though the IAU definition says it’s not a planet. The reason planetary scientists do this is because the IAU definition is not useful for science.”

. . . .  Metzger and his co-authors argue that the IAU definition is invalid because the particular details of an object’s orbit around its host star — in this case the sun — have more to do with the star itself than with the object. For instance, a planet orbiting a massive star will most likely not be able to clear its orbit, whereas that identical planet in orbit around a much smaller star will.

In other words, it doesn’t make sense to base the planet-dwarf planet decision in part on something that is determined by an object’s host star.

“That’s like saying a tiger is not a mammal unless it’s able to clear away all the other predators on the island where it lives,” Metzger said. “That depends not just on what the tiger is, but what else happens to be on the island.”

The New Horizons spacecraft that flew by Pluto in 2015 showed dunes made of solid methane ice, mountain peaks covered in methane snow and, possibly, an icy, underwater ocean. Perhaps the only planetary body in the solar system with more complex morphology and chemistry is Earth.

New Horizons is now just 80 million miles from Ultima Thule, a chunk of ice and rock about 4 billion miles from Earth and generated during the earliest days of the the solar system’s formation.

The spacecraft has already begun photographing Ultima Thule for navigation purposes and remains on track to cruise within a mere 2,200 miles (3,540 km) of Ultima in the wee hours of Jan. 1, 2019. The data New Horizons gathers during that encounter hshould shed considerable light on the solar system’s early days, said mission principal investigator Alan Stern.

“Ultima Thule was formed at the origin of our solar system, and it’s been in this deep freeze ever since,” Stern, of the Southwest Research Institute in Boulder, Colorado, said during a webcast event Wednesday.

“Going to it is like making an archaeological dig into the history of our solar system,” he added. “We’ve never been to anything like this.”

How quickly can Pluto’s misclassification be corrected? Since we are dealing with bureaucrats and egos, not quickly.

[T]here’s a clear way to bring up a motion with the group — “which is to propose an IAU Resolution through the relevant Working Group(s) and Division.”
So far, however, no such resolutions have been proposed, said Lars Lindberg Christensen with the group.

“It is nevertheless good and healthy to debate these topics,” Christensen said.

However, until then, we can go back to teaching that there are nine planets: The science is settled.