Nine decades ago, the largest of the most distant objects in our Solar System was discovered by an observer in America. Even today, it is still king over thousands of similar known objects residing past the gas giant Neptune. All of these objects share many of the same physical characteristics. Some leave their distant neighborhood to embark on a long journey towards and around our Sun, and are known as comets.
The discovery of this one object is a fascinating tale, for it was not found at random. Neptune was discovered 75 years prior, and astronomers had noted over that time that Neptune’s orbit was not quite the same as the other three known gas giants (Uranus, Saturn, and Jupiter). It was thought that a planet similar in size to Neptune and Uranus must lie just beyond the orbit of Neptune, pulling at Neptune via gravity. And so a search was underway.
After its discovery in 1930, the newfound object was thought to be the solution to the Neptune orbit question. As such, it had to be very large. Soon it ranked among our Solar System’s magnificent residents. In short order and for the next half century, it would be counted in science textbooks across America as one of the nine planets orbiting the Sun. This harmonic order was solidified in schools and reinforced by all the amazing advances happening in science generally and our space program in particular.
Also during that half century, astronomers continued to learn and understand so much more about how our Solar System is built. They realized, for one, that the inner four planets (Mercury, Venus, Earth, Mars) are a family of objects. The outer gas giant planets, starting with Jupiter, are another family. Each family was created in their own similar manners and composed of the same basic materials.
More importantly, the inner versus outer distinction among the planets is strongly related. The four inner planets, being so close to the hot Sun, long ago burnt off all their access gas, primarily hydrogen and helium, to leave mostly their rocky cores. The inner planets really are rocks, and we’re on the third from the Sun. By contrast, the outer planets were not close enough to the Sun to burn off their access hydrogen and helium, so they remained, and still do, in their large, gaseous forms. That is why we call them gas giants.
Like an ever-increasing jigsaw puzzle, more and more parts of our Solar System have been revealed thanks to advances in astrophysics. How many parts to the Solar System are there? Classically from ancient times, there were only a handful of planets, including the Moon and Sun. For a while, in the early 19th century, there were more than ten planets accounted for, but eventually those newly-discovered objects, such as Ceres, were determined to be asteroids, a class of objects on their own.
Returning to the object discover almost 90 years ago, it was the first of the newest Solar System class, known today as Kuiper belt objects.
So we classify our Solar System roughly by five major object types:
- The center star, our Sun
- The inner rock planets
- Asteroids, most predominant between the orbits of Mars and Jupiter
- The outer gas giant planets
- Kuiper belt objects, which include comets
Around the same time that this first and largest Kuiper belt object was discovered, an important cultural genesis was happening elsewhere. Mr. Walt Disney was creating his beloved cartoon characters, which are still the core of his Disney empire today. One of these was a dog named Pluto.
Thanks to the intersection of planets traditionally being named for mythological gods and Disney’s cultural phenomenon, a star, err…planet, was born.
First Impressions Are Everything
We all know today the cultural battle – and it is cultural, not scientific – around Pluto’s demotion from the ranks of the other eight planets. What exactly happened, and why is it still such a hot-button issue?
Some 15 years ago, a group of scientists, including Dr. Neil deGrasse Tyson, whose writings on the Pluto affair I base much of this post on, created a museum exhibit in New York to show the scale of the entire universe. When it came to the Solar System part of the exhibit, being good scientists and knowing how Pluto is best classified as a Kuiper belt object, they placed Pluto not with the other eight planets, but with the Kuiper display. Their exhibit made no specific mention of why Pluto was not in the planet exhibit.
This was mistake #1. Culturally, Pluto has been ingrained into every school student for the past 60+ years as one of the nine planets. Pluto was a planet just as the Sun rises and sets each day – it was taken for granted and never questioned by the general public, because they were never given a reason to question Pluto’s status.
But during that 60-year span, astrophysicists gradually realized that Pluto was not like any of the other planets. It is mostly ice, smaller than Earth’s Moon. If Pluto was ever near the Sun, it would form a tail, just like a comet, because Pluto is essentially a comet that never gets close enough to the Sun to start melting off its ice. Its chemical composition is unlike the eight planets as well, but it is similar in makeup to the other Kuiper belt objects that reside at the farthest known space of our Solar System.
So it was obvious in the field of astrophysics that Pluto was unique and separate, but scientists never made mention of this (certainly not enough to change Pluto’s textbook status as a planet), particularly in their universe museum exhibit.
A reporter for the New York Times saw the exhibit, noted Pluto’s exclusion from the other eight planets, and wrote a sensational published article on how scientists unilaterally decided to demote Pluto. At that point, scientists lost the battle for the narrative, because they allowed someone external from their profession to control it. Dr. Tyson claims the exclusion was innocent and not intended to offend, but this reaction only reinforces a problem scientists have even today – they don’t understand that their knowledge has the power to upend common assumptions, and importantly, the aftershocks they can cause.
People prefer stability over change. In a chaotic world, they look for constants. The basics of what every contemporary adult man and woman was taught in elementary school is like a sacred foundation. What happens when you tell them 2+2 no longer equals 4? That is how most everyone reacted to the news that Pluto was, effectively, no longer a planet.
Digging a Hole
Like you, I grew up believing Pluto to be the ninth planet of the Solar System. Like you, I was affronted when the news about Pluto’s apparent demotion began circulating. And like you, I was even more upset when I heard, about a decade ago, that a group of scientists “officially” decreed Pluto no longer a planet.
Dr. Tyson is correct in that if Pluto was not named after a Disney character, the storm around its planetary status may never have gotten so big. It may have flared and then subsided. But Pluto is not just a planet to most, it is a beloved planet. The sacred textbook matter is reinforced by the public’s fondness for something named after a Disney character.
The official reason and decision on Pluto only made matters worse. This was mistake #2. First, nobody (in the general public) is going to be swayed into rethinking Pluto because it has not cleared its orbit of debris. That may make sense to an astrophysicist but not to a New York Times reporter. Secondly, the problem was only compounded by calling Pluto no longer a planet, but a “dwarf planet.”
With apologies to Snow White’s hardworking miners as well as Gimli, nobody and nothing ever wants to be relegated to the status of “dwarf.” Yesterday, you were an apple. Today, you are a dwarf apple, because scientists say so.
The optics of calling Pluto a “dwarf planet” are horrible.
Fruitless Amends
After reading Dr. Tyson’s full explanation, I am thoroughly convinced Pluto is not a planet like the four inner and four outer planets. I contend that any reasonable person who reads Chapter 9 of Dr. Tyson’s co-authored book Welcome to the Universe will agree as well. There was no ulterior motive, no political agenda in demoting Pluto. It was not about making our knowledge of the Solar System fit to keeping Pluto a planet, but recognizing that today’s accumulated knowledge puts Pluto into another class of object.
Mistake #3 has been the ongoing attempt by scientists to make some sort of compromise classification of Pluto, to return it to full planet status. This is an Occam’s Razor matter – any new, refined definition to make Pluto a full planet again comes along with its own complications. Pluto is the largest and most famous Kuiper belt object. That is a grand status on its own. But status is not science. So why are scientists trying to “save” Pluto? Perhaps for the fame of being the savior of a cultural icon is my guess.
I will not say, “Scientists should have done X, Y, and Z to have avoided the Pluto public relations nightmare.” The Pluto matter is about the need for scientists to understand the enormous power they wield, especially as science itself becomes more potent in challenging long-held beliefs. This is particularly true for how scientists communicate their knowledge to the public at large. “You don’t have that option,” to not believe what scientists tell you to believe is no way to dispel the stigma of scientists being arrogant, over-educated fools who want to be your new high priests. Science may be objective, but scientists are still human, complete with their own failings and prejudices. That public figures like Dr. Tyson don’t appreciate their own complicit role in Pluto’s problem is one example of how scientists have to change their strategy for convincing the general public that the causes of science are sincere and real.
Dr. Tyson is likely very much aligned ideologically with his childhood hero, Carl Sagan. Sagan, however, had a demeanor and way about him that invited everyone, regardless of their beliefs, to the knowledge of the cosmos. It is to Sagan’s approach that I would look for the communication answers, not to the contemporary scientist’s abrasive method.
