Response to Tom Hartsfield's Big Think Article, "Searching for Planet 9"

This is a response I sent to the one-sided article "Searching for Planet 9" published April 19, 2022, in Big Think by writer Tom Hartsfield along with a request that I or another writer be given the chance to write a response presenting the other side of this ongoing debate.

As you are likely well aware, the debate over planet definition and over Pluto's status remains ongoing. Just four percent of the IAU voted on the controversial demotion of Pluto and related planet definition, and most were not planetary scientists but other types of astronomers. Their decision was immediately opposed by an equal number of planetary scientists in a formal petition led by New Horizons principal investigator Alan Stern.

Notably, the four percent of the IAU who voted on this misused the term "dwarf planet," which Stern coined back in 1991 to refer to a new subclass of planets by stating in their resolution that dwarf planets are not planets at all but another type of object entirely. Nine years later, this statement was not borne out by the findings of the Dawn mission at Ceres and the New Horizons mission at Pluto.

Since the 2015 New Horizons mission revealed Pluto to be a geologically active world with complex processes seen elsewhere in the solar system only on Earth and Mars, an increasing number of planetary scientists have come to view it as a full-fledged planet

At the Lunar and Planetary Sciences Conference in 2017, planetary scientist Kirby Runyon introduced the geophysical planet definition, which rejects the notion that an object has to clear its orbit to be a planet. Unlike the IAU definition, the geophysical definition focuses on objects' intrinsic properties rather than their location and deems any object that is not a star but is large enough and massive enough to be rounded by its own gravity a planet.

Because so many planetary scientists prefer the geophysical definition, they object to the term "Planet 9" for the hypothetical but as yet undiscovered planet in the outer solar system. Advocates of the geophysical definition count dwarf planets as full planets, so they view the solar system as already having a minimum of 13 planets and counting. In the August 5, 2018, edition of Planetary Exploration Newsletter, a publication of the Planetary Science Institute, a group of planetary scientists objected to the insensitive, one-sided use of the term "Planet 9," noting the IAU planet definition is "far from universally accepted."

Instead, they requested this hypothetical world be referred to by the standard term for a hypothetical but as yet undiscovered planet, which is "Planet X," with "X" referring to the unknown rather than to the number 10.

Hartsfield's article unfortunately begins with an extremely one-sided statement, "The former planet 9, Pluto, was knocked out of the club because it failed to meet the definition of a planet" without noting that that definition is just one of several currently in use and remains controversial to this day.

It then continues with the article's first sentences reading, "Our solar system once possessed nine planets. Then we kicked Pluto out of the club because it was just one of several little things beyond Neptune. Pluto happened to be the largest of them, putting it right on the line between planet and Kuiper Belt speck. The hunt is on for the real planet 9--if it exists."

This sentence contains multiple problems. There is no "we" that kicked Pluto out of the club. The sentence assumes a level of consent that never existed, especially among planetary scientists. It does not even acknowledge the fact that most planetary scientists reject the IAU definition and have done so for over 15 years.

Furthermore, Pluto is far from a "Kuiper Belt speck" or even an object between a planet and a speck. Such a statement totally ignores the New Horizons findings, which found Pluto to have planetary processes such as geology and weather, likely geological layering, floating glaciers, a layered atmosphere, interaction between its surface and atmosphere, varied terrains, windswept dunes, cryovolcanism, and a likely subsurface ocean. No Kuiper Belt "speck" has these features; such specks, like asteroids, are simply loosely held together by their chemical bonds.

Big Think's readers deserve a far more fair and balanced reporting of this issue, which acknowledges the ongoing debate and both positions instead of portraying one side as fact. There are many planetary scientists who would be happy to write about this for you, and I would be happy to get you in touch with them.

Response to Matthew Rozsa's Salon Article, "Pluto Wasn't the First"

I sent the message below to several editors at Salon.com regarding an article by Matthew Rosza, published on April 17, 2022, titled, "Pluto Wasn't the First: A Brief History of the Solar System's Forgotten Planets" because the majority of this article is very one-sided in terms of the planet definition debate and therefore calls for a response.

I am writing to request you publish an article of mine responding to Matthew Rosza's April 16,2022, Explainer article, "Pluto Wasn't the First: A Brief History of the Solar System's Forgotten Planets." Although at its end, this article acknowledges that some scientists reject the controversial IAU demotion of Pluto, it is mostly very one-sided in its depiction of the planet debate and Pluto controversy, and unfortunately, there is no comments section on the site for people to respond.

Rosza neglects several important points, beginning with the fact that just four percent of the IAU voted to demote Pluto, and most were not planetary scientists but other types of astronomers. Their decision was immediately opposed in a formal petition by an equal number of professional planetary scientists, yet the mainstream media never reported this fact.

Kindergartners in 2006 did not necessarily .learn a different number of solar system planets than those in 2005 did because many educators also opposed the controversial demotion of Pluto and continued to include Pluto when teaching the solar system.

The analogy to Ceres, made for the last 15 years, is also flawed. According to the geophysical planet definition, which most planetary scientists prefer, Ceres IS a planet because it is rounded by its own gravity, a state known as hydrostatic equilibrium. However, this was not known in the 19th century when it was demoted, because telescopes of the time could not resolve Ceres into a disk. Now they can, which is why it is clear the 19th century demotion was  in error. Vesta and Pallas are also not really asteroids; they are considered protoplanets because they appear to have once been spherical only to have had a portion lobbed off in an impact. This makes them very different from true asteroids, which are tiny, shapeless, and held together only by their own chemical bonds.

Additionally, Pluto may have a frozen surface, but data and images from the 2015 New Horizons flyby strongly suggest it has a subsurface liquid ocean (which Ceres may also have) and an internal heat source. This means both Pluto and Ceres are more akin to icy moons like Europa and Enceladus and could potentially support microbial life. While Pluto is often described as an ice world, it is actually 70 percent rock and likely geologically differentiated into core, mantle, and crust just like Earth is.

Saying astronomers once thought Pluto and Ceres should be planets but then "changed their minds" and that Pluto "lost its planet status" because "astronomers had decided there were three criteria for being considered a planet" is an incorrect over-generalization because these decisions were made by only a small number of professionals and largely by those in fields of astronomy other than planetary science. There was NEVER a consensus among planetary scientists on this. Furthermore, saying Pluto "lost its planet status" because of a vote inherently assumes science is done by decree of "authority," a very unscientific statement that essentially went out with Galileo.

Furthermore, the four percent of the IAU who voted on the 2006 resolution misused the term dwarf planet, which was coined by New Horizons principal investigator Alan Stern in 1991. He coined this term to designate a new subclass of planets, not to designate a class of non-planets. In astronomy, dwarf stars are a subclass of stars, and dwarf galaxies are a subclass of galaxies. Claiming that dwarf planets are not planets at all makes no sense and runs counter to the findings of the Dawn and New Horizons missions, which found both Ceres and Pluto to have planetary processes similar to those of the terrestrial worlds.

As a science writer and blogger who has run a blog opposing the IAU decision for over 15 years and has written and spoken extensively on this topic, I respectfully request you allow me or someone else (ideally a planetary science) to write a response to this article clarifying these points and explaining that this issue has been and remains a subject of ongoing debate.

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Discovery Anniversary: People still care very much about Pluto

Ninety-two years ago today, on February 18, 1930, Clyde Tombaugh discovered the planet Pluto while blinking photographic plates of the night sky taken several nights apart at Lowell Observatory in Flagstaff, Arizona. In the decades since then, Pluto’s discovery has become more appreciated and more celebrated than he could have imagined on that day.

Once again, the Lowell Observatory is celebrating the anniversary with a multi-day “I Heart Pluto” festival. This year’s is a hybrid event, with many online presentations as well as an in-person evening of entertainment and activities tonight at the Orpheum Theater and a historic walk tracing the steps Clyde Tombaugh took on that day following his discovery. Tombaugh actually spent that evening at the very same Orpheum Theater.

A source at the observatory informed me that tonight’s presentation will be recorded and placed online in the near future.

While more people than ever are coming to appreciate and celebrate this small, unique planet, something interesting is happening. Supporters of the IAU planet definition and of Pluto’s demotion constantly argue that few people care about Pluto’s planet status, that only a few “holdouts” refuse to accept the demotion.

Yet every time Pluto is in the news, this claim is proven to be blatantly false.

This week, Edward Gleason of the Southworth Planetarium in Portland, Maine, who supports Pluto’s planet status, addressed the debate over Pluto’s planet status in an email message sent to friends of the planetarium. The next day, he followed up with a post stating that he received multiple responses on this issue, “all of which were in equal measure thoughtful and passionate.”

He even quoted my response to his question, "The IAU General Assembly is convening its next meeting this August in Korea. Will Pluto's planetary status be then reinstated?" in which I noted that we don’t need the IAU for Pluto to be considered a planet.

I wrote: “Statements like this assume that only the IAU has the right to bestow planet status on an object. This is essentially an appeal to authority. The IAU planet definition should not in any way be privileged above other definitions currently in use, such as the geophysical definition. I have long suggested planetary scientists form their own organization and adopt their own definition of planet. We do not need the IAU to issue a decree or stamp of approval for Pluto to be considered a planet. Unfortunately, the media has portrayed the IAU decision as fact rather than as what it really is--one side in an ongoing debate.”

And he agreed, stating: “Indeed! That line does presuppose that the IAU stands as the final authority on all such matters.   We know that most planetary scientists have ignored the IAU's designation, a fact little mentioned by most media sources.  I stand cheerfully corrected.”

Gleason’s experience receiving so much feedback regarding Pluto is not unique. Planetary scientists and amateur astronomers who do public presentations and/or write articles on this subject are regularly asked about Pluto and its planet status. Fascination with this tiny, active world, and healthy skepticism about the IAU decision has only grown stronger over the last 15-and-a-half years.

When someone, whether a scientist, a writer, an amateur astronomer, or a member of the public claims that no one cares about Pluto’s status, what they are really saying is that they think no one should care. It usually means they support the IAU planet definition and its claim that dwarf planets are not planets and want to have the last word on the issue.

And their related statement, that Pluto doesn’t care what we call it, is irrelevant. The issue isn’t whether Pluto cares, but why we should care. As Philip Metzger notes, taxonomy is how we make sense of the world. It is integral to science. The IAU’s taxonomy is flawed because it lumps two very different types of objects—asteroids and comets on the one hand, and dwarf planets on the other—into the same category of non-planets.

Too often, one will read articles online that claim our solar system has just two types of planets—terrestrials and jovians—and/or cite the names of the four terrestrials and the four jovians, then add in the asteroid belt and Kuiper Belt to describe the solar system.

But objects like Ceres and Pluto are far more than just small objects in belts, and they differ significantly from the majority of the tiny objects in those belts. Describing the solar system as having just rocky planets, gaseous planets, the asteroid belt, and the Kuiper Belt erases the existence of these small planets, which have more in common with rocky worlds like Earth and Mars than they do with KBOs like Arrokoth.

In a presentation on the glass plates which were used in Pluto’s discovery, one of Lowell Observatory’s speakers who knew Clyde Tombaugh reported that Tombaugh said he immediately recognized the tiny dot whose position moved against the background stars from one plate to another via the blink comparator. That tiny dot is part of a huge star field, and most people aren’t likely to find it even after hours of blinking the two plates.

Pluto was discovered in a unique way, by a very unique, intelligent, and skilled individual. The people of the world deserve to know about this amazing, very much alive little planet. Typically, the more they learn, the more their fascination grows.

In spite of the IAU’s decade-and-a-half false narrative, the people have spoken. And they continue to overwhelmingly recognize Pluto—and all dwarf planets--as a planet.