Planet Pluto at 89: Biased IAU Documents Reveal Depth of Denial

Today marks the 89^th anniversary of Pluto’s amazing discovery by 24-year-old Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona, on February 18, 1930.

With this year’s New Year’s flyby of Kuiper Belt Object Ultima Thule, Tombaugh, whose ashes are onboard the New Horizons spacecraft, became the only person to have ever journeyed four billion miles from Earth, on a trajectory to eventually leave the solar system.

Back on Earth, the diminutive but fascinating planet he discovered almost nine decades ago continues to fascinate people of all ages, including children who, though born after the ridiculous IAU vote, continue to view Pluto as a planet.

Unfortunately, the IAU has made no attempt to rectify its 2006 blunder. At its 30^th General Assembly (GA) in August 2018, the first GA held since all of New Horizons’ data on the Pluto system was returned in late 2016, the IAU made no effort to revise its definition based on the new data or update it to include exoplanets.

Incredibly, some materials distributed at this year’s IAU GA regarding the New Horizons Pluto flyby contain erroneous or misleading information. Most prominently, an image of Pluto and Charon that is part of the IAU’s 100th Anniversary Exhibition, which the group plans to display worldwide over the next year, while composed of New Horizons images, inaccurately portrays the size difference between the two worlds. A very small Charon is shown to the bottom left of Pluto. Charon is actually half Pluto’s size, meaning it is scaled down by around a factor of four in this image. The use of real photographs makes the display appear authentic, yet it is far from that, as Charon is large enough for the center of gravity between it and Pluto to be between the two objects, making Pluto-Charon a binary planet system.

The IAU’s 72-page Strategic Plan 2020-2030 gets the mission name wrong by referring to it as “New Horizon” without the “s” on page 55, but this is the least of its problems. Every reference to the New Horizons mission and/or the solar system seems deliberately worded to convey the message that its 2006 decision is set in stone, never to be changed.

On page 23, a diagram of the solar system positioned next to a much too large image of interstellar asteroid ‘Oumuamua, shows the orbits of only Mercury through Neptune. Page 27 shows the Mitaka Solar System Walk in Japan, with a poster clearly showing the orbits of only eight planets.

Then, at the top of page 55, in a discussion of the New Horizons and Rosetta missions (Rosetta orbited Comet 67P/Churyumov-Gerasimenko), a sentence that seems written deliberately to deny Pluto’s planet status says, "Recent space missions such as Rosetta and New Horizons have provided a wealth of data on the physical characteristics of asteroids, comets and the outer Solar System." There is no mention of New Horizons having visited a small planet as its primary mission.

Additionally, at last year’s GA, the IAU published a self-congratulatory paper written by Ron Ekers that amounts to a poster child of denial regarding the worldwide impact of its 2006 vote. Titled “The Prague IAU General Assembly, Pluto, and the IAU Process,” this document, which I am including here, reveals just how out of touch the IAU is, with claims that “The IAU planet definition has had a large impact and while there was, and still is, a vocal minority, the general reaction has been positive.” Among examples of this supposed “positive” reaction, the report cites “burial services” for Pluto “held at some public science centers that (supposedly) were used to explain the way science progresses.”

Another inaccuracy in the report relates to the 2005 discovery of Eris. Ekers writes, “One TNO (Trans-Neptunian Object), 2003 UB313 (the original designation of Eris), which was found by Mike Brown at Caltech was estimated to be larger than Pluto (e.g. Brown et al, 2006a)…” In a very unprofessional manner, Ekers fails to note that Eris was actually discovered by a group of three scientists rather than by Brown alone. The other two, Chad Trujillo and David Rabinowitz, reject the IAU planet definition; Rabinowitz even signed a petition by 300-plus planetary scientists opposing the definition, circulated within days of the IAU vote. Furthermore, in 2010, the belief that Eris is larger than Pluto was proven false when a team of scientists led by Bruno Sicardy obtained a more accurate measurement of Eris when it occulted a star. Conveniently, the IAU report neglects to mention this.

In fact, the eight-year-old error regarding Eris is repeated in the first sentence of Item 3, which reads, “The boundary between (major) planets and minor planets has never been defined and the discovery of 2003 UB313, a TNO larger than Pluto, was the trigger for the IAU to act.” Unbelievably, this, along with the erroneous claim that Brown alone discovered Eris, is repeated a third time, with the statement, “With the planet definition settled, 2003 UB313 is a dwarf planet (the largest known) and was appropriately named Eris by its discoverer Mike Brown, Eris being the goddess of strife and discord!”

While the report goes on to name the members of the Planet Definition Committee formed by the IAU in 2006, it fails to mention that following the rejection of that committee’s definition by the General Assembly, the alternate resolution that was hastily thrown together was done so in violation of the group’s bylaws, which require all resolutions to be vetted by the proper committee before placed before the General Assembly for a vote. It also neglects to report that Planet Definition Committee chair Owen Gingerich, who was unaware of this subterfuge and left the conference early, later stated that had he known another resolution would have been put to the GA floor, he would have stayed until the end.

A hesitant acknowledgement of the bylaws violation is recognized with the statement, “Obviously, the continual redrafting of resolutions during the GA was less than optimal, but it did demonstrate an active process of consultation.” Ekers also grudgingly admits the exclusion of planetary scientists in the decision by stating, “Holding the debate at the GA in public had a huge and positive impact on all except some planetary scientists who were not attending this GA and felt excluded from the action.”

Incredibly, the report includes nothing on New Horizons’ discoveries at Pluto, other than to say, “Obviously, the IAU resolution was not relevant for this remarkably successful mission but now we can say that New Horizons was not only exploring the first TNO but also discovering how spectacularly different are the Dwarf Planets.”

This description is actually the opposite of what New Horizons discovered! The probe revealed how similar, not how different, Pluto’s processes and structure are to those of its larger terrestrial counterparts, specifically by revealing evidence of cryovolcanism, a layered atmosphere, interaction between the atmosphere and the surface, the presence of wind-blown dunes, floating glaciers, active geology, and a possible subsurface ocean. Nothing in New Horizons’ findings showed this particular dwarf planet to be “spectacularly different” from the objects the IAU defines as planets. Incredibly, Ekers had to resort to a lie to make his point.

The report’s epilogue, which features a list of all the “positive reactions” to the IAU vote, including the earlier mentioned “burial ceremony,” is actually a litany of biased sources, all who favor the IAU definition: Mike Brown, journalist Daniel Fischer, astronomer Jean-Luc Margot, Neil de Grasse Tyson, etc. This highly political rather than scientific list is the equivalent of someone arguing that the response to the recent shutdown of the US government by President Donald Trump was a complete success by citing solely those who support it (or vice versa). Ignoring the other side and pretending it does not exist are not science but propaganda.

To add insult to injury, the only “less positive reactions” the report bothers to cite are either humorous ones, such as a joke about the IAU claiming February is not a month, legislation by Illinois and New Mexico rejecting the definition, and the American Dialect Society choosing “Plutoed” as 2006 word of the year, or those lacking credibility, such as opposition to the demotion by astrologers. Somehow, the petition signed by 300 plus planetary scientists opposing the definition and the subsequent articles, publications, presentations, and public referendums over the next 12 years are never mentioned.

Ironically, Ekers concludes by stating, “The need for electronic voting was recognized and included in the IAU Statutes as a result of the Pluto debate.” The reality is, the need for electronic voting was actually something promoted by opponents of the IAU decision, who noted that 96 percent of its members could not vote in 2006 because there was no provision for electronic voting. Both scientists and members of the public requested the enacting of electronic voting for six years before the provision was finally adopted by the organization in 2012.

In 2006, the IAU leadership made a big enough deal about the discovery of Eris to merit a debate on defining the term planet. Yet in 2018, when sufficient new data had been revealed by New Horizons to the point of completely rewriting our understanding of the Pluto system, this same leadership barely acknowledged the findings.

When, back in 2006, the IAU was confronted with the fact that its definition only applied to our solar system and not to exoplanets, they promised to address exoplanets sometime in the future. Since then, we have gone from approximately 300 known exoplanets to about 4,000, but they have yet to address the issue.

The fact that there has been no effort to update the definition to include exoplanets and no recognition of the new data about Pluto returned by the New Horizons mission makes it clear we have reached a major turning point in the quest for a better, geophysical planet definition.

These fake news IAU documents need to be exposed and refuted. Cherry-picking data to prove one’s pre-existing bias is not science. Clyde Tombaugh is not here to do this, but for the sake of knowledge and of future generations, the world needs an organized effort by planetary scientists to do it and finally set the record straight for educators, textbook publishers, the media, and the public.

The small world discovered 89 years ago today was, is, and always will be, a planet.