Pluto: Ten Years Since the IAU's Epic Fail

After the 1920s debate over whether the universe is composed of one galaxy—the Milky Way—or of many galaxies was resolved with definitive evidence for the latter position, the controversy was resolved.

Our universe contains billions of galaxies, including structures once referred to as “spiral nebulae” erroneously thought to be located within the Milky Way.

After observations conducted during the May 1919 total solar eclipse confirmed Einstein’s theory of general relativity, showing the position of stars near the Sun slightly shifted from their actual locations, general relativity was accepted worldwide as being true—and as the reason for the strange precession of the planet Mercury’s perihelion (point closest to the Sun).

But ten years after the controversial and highly problematic planet definition adopted by four percent of the IAU, most of whom were not planetary scientists but other types of astronomers—that definition remains as contested as it was on day one.

Rather than bringing a resolution to the debate, as did the evidence in the two previous examples, the IAU vote heightened that debate and resolved nothing.

It actually did harm to science by confusing the public into thinking science is done by voting and by imposing a definition that contradicts everything people see when observing close-up photos of Pluto.

Back in 2006, no such close-ups of Pluto existed. However, the IAU knew fully well that the New Horizons probe, launched seven months before that year’s General Assembly, was on its way to Pluto and would provide a wealth of images and data in July 2015.

They also knew that the Dawn mission was scheduled for a launch the following year, and it would visit Ceres and Vesta, two objects that orbit between Mars and Jupiter, both of whose statuses as asteroids were questionable.

The scientifically correct action would have been to wait until the data from these missions came in before trying to classify objects no one ever viewed as more than tiny dots.

Unfortunately, several astronomers, motivated by their own personal agendas, did not want to wait for the results. Leading that group was the late Dr. Brian Marsden, who had expressed his desire to see Pluto demoted from planethood to discoverer Clyde Tombaugh back in 1980.

When a team of three astronomers discovered a planet beyond Pluto initially thought to be bigger than Pluto, now known as Eris, some of these astronomers jumped at the opportunity to use the discovery as a means of imposing their agenda.

They claimed that if the new object is larger than Pluto and yet is not a planet, then Pluto could not be a planet either.

In 2010, when Eris occulted a star, a different group of astronomers led by Dr. Bruno Sicardy determined it is marginally smaller than Pluto though 27 percent more massive.

Even if Eris were larger than Pluto, why would its discovery prompt any sense of necessity to come up with a specific definition of planet? So what if our solar system has 10 planets or 11, or 50? Most people actually find it exciting to learn that the solar system has many more planets than anyone ever thought.

What should have happened is that Eris should simply have been added as yet another solar system planet.

But in addition to personal agendas, some astronomers came up with the ridiculous idea that our solar system cannot have “too many planets” because kids won’t be able to memorize all their names.

That argument is no more rational than stating we have to limit the number of stars and galaxies to something countable, or that we have to limit Jupiter’s moons to four because no one can memorize the names of 67.

Memorization is not critical to learning. Once upon a time, little was known about the planets other than their names, their order from the Sun, and estimates of their sizes.  At that point, there wasn’t much else to teach about them.

Today, things couldn’t be more different. With the dawn of the space age, we have robotically visited every single one of the nine classical planets as well as Ceres and Vesta. We know the complex processes many of them and many of their moons undergo, their compositions, and their surface features.

Instead of asking children—and adults—to memorize a list of names, we can teach them the characteristics of the different subclasses of planets such as terrestrials, gas giants, ice giants, dwarf planets, proto-planets, super Earths, hot Jupiters, hot Neptunes, etc.

The latter three are not present in our solar system but do exist in other star systems.

Ten years ago, in essence, the IAU concocted a reason to issue a decree that was never needed. Its members then set out to craft a definition that achieved the results they desired, namely excluding Pluto.

And they established a definition with a requirement that set Pluto’s status in stone. No matter what would be discovered by New Horizons, Pluto could never again be a planet because its intrinsic characteristics meant nothing. The only thing that counted was whether it cleared its orbit.

Orbit clearing may be useful in terms of understanding the effects celestial objects have on other objects, but making it a requirement for planet status makes absolutely no sense.

The further an object orbits from its parent star, the larger an orbit it has to clear. That makes the definition inherently biased against planets in distant orbits from their stars.

Furthermore, it perpetuates an erroneous conception of objects like Pluto and Ceres, leading people to think these worlds are surrounded by numerous objects in their orbits in an asteroid field similar to the one through which Luke Skywalker piloted the Millennium Falcon in Star Wars.

Yet nothing could be further from the truth. Both the asteroid and Kuiper belts are huge, with vast distances between objects residing in them. This is why New Horizons did not have to use one of its contingent trajectories to fly through the Pluto system. Those trajectories were based on a need to avoid debris that might be floating around near Pluto.

But there was no such debris, which New Horizons scientists attribute to Pluto’s large moon and binary companion Charon having swept it all from the system.

If KBOs were really so close to one another in a crowded belt, why could only the Hubble Space Telescope find a few close enough KBOs in New Horizons’ path for a visit after Pluto? From the way people talk about the Kuiper Belt, one would have thought there were numerous small objects nearby.

Haumea, Makemake, Eris, and other, more recently discovered dwarf planets are not in Pluto’s orbit unless one counts the entire Kuiper Belt as part of Pluto’s orbit—a proposition that makes no sense, as the belt is huge, and the majority of it is located well beyond Pluto.

Yet, because of the IAU definition, many people are under the misconception that many objects larger than Pluto have been discovered in the Kuiper Belt and that the entire region is a zone crowded with ice balls and rocks.

While there could be planets larger than Pluto out there, so far none has been discovered.

Astronomer Mike Brown, who co-discovered Eris, earlier this year publicly hypothesized the existence of a large planet far beyond Pluto, which, to add insult to injury, he deliberately referred to as “Planet Nine,” clearly for no other reason than to snub those who still consider Pluto a planet.

Now, when we have a wealth of data and images about Pluto, certainly sufficient new information to re-open the planet debate yet again, the IAU has no interest in doing so. Why does some new data in 2006 justify IAU action yet a huge inundation of new information in 2016 not inspire similar action?

It is not just the IAU that is at fault here. The media has been misrepresenting this issue for a decade now. From day one, they should have questioned the IAU definition and consulted the many planetary scientists who signed a petition disagreeing with it. Instead, they reported the decision as fact, calling Pluto an “ex-planet,” and stating that textbooks and teachers now have to change their teaching of the solar system to one of eight planets.

The media also unprofessionally blindly accepted Brown’s use of the term “Planet Nine” for the hypothesized large planet yet to be discovered when what they should have done is referred to it by the standard appellation for undiscovered worlds, which is “Planet X.”

Where the media failed big time is in accepting the IAU decree at face value instead of critically pointing out that science is not determined by “authority” but by a preponderance of evidence for a theory or position.

They also failed to inform the public that most of the 424 IAU members who voted in 2006 were specialists not in planetary science but in completely different fields of astronomy. Why would a person who studies black holes be considered an expert on planetary science? Would the media accept a decree by planetary scientists about the nature of black holes?

The fact that the IAU definition is still so contentious a decade after its adoption is itself evidence that it was and is an epic fail.

Interestingly, even children born after the vote still consider Pluto a planet. When I worked as a performer in the New Jersey Renaissance Faire playing a court astronomer/astrologer, I asked children what their favorite planet was, and Pluto was the number one answer, followed by Earth.

That is usually when I shared that in the 1560s, calling Earth a planet was considered controversial, as it amounted to an affirmation of Copernicanism, which stated the Sun is the center of the solar system and the Earth simply a planet orbiting the Sun.

New Horizons Principal Investigator Alan Stern reports that the status issue is raised at every single talk he gives about New Horizons and Pluto, even if he does not mention the controversy in his presentation.

Because planetary scientists do not have a formal organization like the IAU, they do not have a means to organize and promote an alternative point of view. That, however, does not mean that that alternative view does not exist.

As for the claim that Pluto cannot be considered a “major planet” due to its small size, the real problem is the false dichotomy inherent in using the terms “major” and “minor” planet. As David Weintraub notes in his book Is Pluto A Planet, the term “minor planet” has been used for more than a century to refer to asteroids and comets, objects too small to be rounded by their own gravity. These are the objects the IAU accurately refers to as “Small Solar System Bodies.”

But Pluto and Ceres—and all dwarf planets—are not asteroids, so the term “minor planet” is not appropriate for them. A better schematic is to do away with the terms “major” and “minor” planet altogether and replace them with terrestrials, jovians, and dwarf planets, all of which fall under the umbrella of planets. Objects like Vesta and Pallas, which are larger and more complex than asteroids, could comprise yet another planetary subcategory, “proto-planets.”

A decade after a controversial vote allegedly changed everything about the way we understand our solar system but really changed nothing, planetary scientists, professional and amateur astronomers, and members of the public overwhelmingly continue to view Pluto as a planet, especially in light of the geologically complex world New Horizons found.

Public usage, not a decree from an isolated, self-appointed group of “experts,” will determine which view enters into posterity. From the last ten years, it is clear that when it comes to Pluto, that view will not be the one advocated by four percent of the IAU.

Adored worldwide, the little planet that would not die is so very special that it will be there for eternity.