Pluto at 88: The Debate Continues

Pluto, known to humanity just since 1930, has been a solar system planet for four billion years but was discovered as one 88 years ago today, on February 18, 1930, by astronomer and planetary scientist Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona.

An article published yesterday in TheWashington Post reports that six-year-old Cara Lucy O’Connor of Ireland, with the help of her teacher, wrote a letter to NASA asking the agency to reinstate Pluto as a planet. Based on Cara’s statements in the article, it is fair to say she knows more about the solar system than most adults and maybe even more than the 333 non-planetary scientists at the 2006 IAU General Assembly who voted for the resolution that says dwarf planets are not planets at all.

Especially interesting are the comments written in response to the article, many of which are replete with the same errors and misconceptions that have now been repeated for 11-and-a-half years.

While Cara cannot be expected to know this, the controversial vote to demote Pluto was not made by NASA but by four percent of the IAU. Contrary to some people’s comments, NASA does not formally accept or reject the IAU decision. Instead, the agency leaves that decision up to its individual scientists. This is why some NASA websites continue to include Pluto as a planet while others do not.

Most scientists on NASA’s New Horizons mission do consider Pluto and all dwarf planets to be a subclass of planets. Since this group actually flew a probe to Pluto, the last thing NASA is likely to do is tell them they are wrong. Thanks to the mission team, humanity has seen Pluto up close and has learned more about this geologically active world than was known prior to the 2015 flyby during the 85 years since its discovery.

Among the misconceptions repeated in the comments are that there are Kuiper Belt Objects out there that are larger than Pluto (there are none known though even if there were, that would not preclude all of them from being considered planets), that the “experts” of the world made a scientific decision that has broad consensus among scientists ( they didn’t, and it doesn’t), that being in a belt of objects is the primary determinant of what an object is (this completely ignores an object’s intrinsic properties), that the Lambda factor in Alan Stern and Hal Levison’s 2000 paper precludes dwarf planets from being planets (it doesn’t), that Stern alone has a personal interest in Pluto being classed as a planet (he is far from alone; most planetary scientists take this same position), and that the number of planets has to be kept small because people can remember only at most ten numbers in a sequence (this is erroneously based on the notion that memorizing a list of names is the way to teach kids about the solar system).

In many ways, the IAU vote is a lot like climate change science funded by oil companies and other industries with special interests in a particular outcome. Those working on these studies know where their money is coming from and set out to “prove” a foregone conclusion in favor of their funders. So, too, the four percent of the IAU who voted in 2006 had a prior agenda of excluding Pluto from the list of planets. They then crafted a definition that met the conclusion they had already decided on. That is where the orbit clearing “requirement” came in. What we have here is something that looks like science but is not the real thing.

Some writers mock Cara with condescending remarks about how scientists should not give in to the “whim” of a child. Others frighteningly buy into the notion that the IAU is the body of experts who have been “empowered” by the world to make such decisions.

Nobody has so “empowered” the IAU. The organization appointed itself to do this, in spite of the fact that its true mission is to “safeguard the science of astronomy.” As I have noted many times, most of the 424 IAU members who voted in 2006 were not planetary scientists but other types of astronomers—hardly the ones who should be telling the world what is and is not a planet. IAU definitions are intended for internal organizational use, not meant to be imposed on the entire world. And no one raises the issue that science is not dictated by decree of “authority.” Galileo addressed this notion 400 years ago, yet it seems some have not learned the lessons of his experience. Like today’s planetary scientists, he observed phenomena that contradicted the decrees of the “authorities” of his day. He saw that Jupiter has moons, that Venus has phases, that the Moon has craters and diverse features, that the Milky Way is made up of numerous individual stars—and was not afraid to publicly present his findings in contradiction to those “authorities.”

Other comments include the old staples about how “Pluto doesn’t care” what it is called, a need to accept change based on new discoveries, claims that Pluto is fundamentally different from the larger planets, and even political statements regarding Barack Obama and Donald Trump.

I have no idea what position, if any, these politicians and others take regarding Pluto’s status. What I do know is that whether or not Pluto is viewed as different from the other planets is largely based on the criteria people choose for basing their decisions. Pluto has active geology, cryovolcanism, an atmosphere, interaction between that atmosphere and its surface, and a possible underground ocean. It is geologically layered into core, mantle, and crust. As for its eccentric orbit, Mercury also does not orbit on the same plane as most solar system planets, and many giant exoplanets in individual systems all orbit on different, far more eccentric planes than Pluto.

The argument that “Pluto doesn’t care” what it is called is a straw man. No one is saying Pluto does care. Instead, the point is that we should care because the public is being sold a bill of goods by being taught that one view in an ongoing debate is gospel truth. This is the tremendous disservice to the public caused by the IAU vote.

Why do so many textbooks, media outlets, websites, and educational materials report nothing about the ongoing debate over the status of dwarf planets, instead blindly falling in line with the IAU position? Why did Encyclopedia Britannica wait for the IAU vote to publish its 2006 edition? Both children and adults are being taught a falsehood as truth. They are being led to believe there is consensus on one specific interpretation of the solar system when this is far from the case.

The IAU has had its chance to rectify its mistake of determining what Pluto is before any spacecraft ever visited it and has repeatedly refused to do so. Apparently, only some new discoveries merit reopening the debate. Eris’s discovery does, but New Horizons’ findings of planetary processes on Pluto apparently do not.

Instead of giving this organization a degree of power it has never earned, it is time to look elsewhere for insight into what constitutes a planet. While this is an ever-evolving question that will always change with new discoveries, those we should look to for guidance are the scientists who actually gave us a first-hand view of Pluto, not a group of bureaucrats concerned largely about preserving their own power.

Finally, we often hear the argument that if Pluto were discovered today, it would not be considered a planet. This, too, is an interpretation. As we can see, the status of Eris, discovered in 2005, set off the latest round of this debate, which continues to this day. If Pluto had been found today, scientists would quickly be able to view it with the Hubble Telescope and determine it is spherical. They would be able to tell it is part of a binary planet system with Charon that also has four more tiny moons. They would be able to determine Pluto has an atmosphere and even visit it up close with a probe. It is fair to say that if Pluto were discovered today, the same debate over its status would occur.

Cara’s precociousness is reminiscent of that showed by another young person, who built his own telescopes, observed Mars and Jupiter, and drew very accurate depictions of those planets that earned him the job of searching for a new planet at Lowell Observatory—a planet he discovered 88 years ago today. Clyde Tombaugh never wavered on his position that Pluto is a full-fledged planet. Neither should Cara, and neither should we.