Celebrate Victory at the Winter Solstice

 

I apologize for being late with this good news though most who follow the New Horizons mission have already heard it—specifically, we won! New Horizons will continue to be a planetary mission while also doing heliophysics in the distant Kuiper Belt. Its team will also continue to search for a third Kuiper Belt Object (KBO) for a close flyby.

This victory belongs to the New Horizons team and to more than 7,000 people who signed the online petition to keep New Horizons a planetary mission with the crew it has had since before its 2006 launch.

According to petition organizer Hoyt Davidson, “The New Horizons team believes our petition and the cover letter to NASA’s leaders really was the straw that broke this loose.”

For more on where the mission goes from here, visit https://www.nasa.gov/missions/new-horizons/nasas-new-horizons-to-continue-exploring-outer-solar-system/ .

When so many of us were fighting to keep the planetary mission, I suspected things would end this way but was afraid to be too hopeful.

While this win happened at the end of September, today, when we commemorate the Winter Solstice and look back at the past year, is an opportune time to celebrate this accomplishment.

For the latest on New Horizons, check out this blog post by principal investigator Alan Stern: https://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_12_19_2023&fbclid=IwAR1d2x8GTgzxBoNG_XSS_GkMcgDd-_8QCGuq9PttzPx-4G5-4KVBToZNUrE

At its core, the Winter Solstice is about hope, about the promise of new light and new life on the longest, darkest night of the year. In ancient times, people would come together to light bonfires they kept burning all night to “strengthen” the Sun and help it return.

How different is that from people all over the world coming together to fight for New Horizons? This, after all, is how the mission was created and launched after multiple cancellations and numerous obstacles. People came together for a project in which they believed and refused to give up on it.

We have always had the power to create change, to make the world a better place, to bring light to the darkness.

In these days of extreme weather and climate disasters, we need to find that power within and come together to save the habitability of our world and to explore beyond it. May we embrace and express that power in 2024 and beyond.

“Darkness does wane though winter’s chill

The season reigns so bitter still

Fire’s bright seed is born anew

Small spark of light we sing to you!

Birthday of light we hail and cheer

Though short the days still cold and drear

Solstice has come, and with this morn

Our brother Sun has been reborn!”

~Rich Mertes, fourth grade teacher, https://www.youtube.com/watch?v=LazGbmTcJHw

End of the Chase for New Horizons?

End of the Chase for New Horizons?: How the journey taken from start to implementation of the incredible New Horizons mission is facing derailment, something that has echoes from the past.

The Pluto Resistance Continues

Here we are. It’s that day again—the day that will live in infamy, when 424 IAU members engaged in a throwback to the 16th century and attempted to impose a very flawed planet definition on all of humanity. At that time, there were six billion plus people on Earth. Today, there are over 8 billion.

Yet the bigger mistake and public disservice was not by the IAU but by most of the media and educational establishment. By giving the IAU definition the force of law instead of recognizing it as just one view among several in use, they too engaged in medieval behavior.

In an upcoming entry, I will share a comprehensive Power Point presentation by writer Jack Mitch Culberson. Some of the images come from this blog, but most are from other sources. He accurately described the IAU vote of 2006 the way the media should have done.

Culberson stated, “The IAU no longer considers Pluto a planet.” THAT is what should have been and should be reported—not “Pluto stopped being a planet.” Not only is the latter statement equal to science by decree of authority; it also completely glosses over the fact that an equal number of planetary scientists rejected that definition and to this day, prefer the geophysical definition, according to which all dwarf planets are a subclass of planets.

When Galileo looked through his telescope in 1610 and saw mountains on the Moon, the phases of Venus, and the moons of Jupiter, scientist Cesar Cremonini declared him wrong and refused to even look through his telescope. After all, Aristotle had already determined the Moon is a perfect sphere. If one already knows the “truth,” why look at additional evidence?

In 2015, the IAU did essentially the same thing Cremonini did, with the same inaction. Having made up their minds that a planet has to “clear its orbit,” they refused to look with new eyes at data about Pluto sent back by New Horizons, which clearly showed it to have complex planetary processes. The 2005 discovery of Eris was viewed as new data that merited a redefinition of the term planet, but the first ever images and data that revealed Pluto to be a planet, did not merit that same consideration to them.

And the media mostly enabled their denial.

The news isn’t all bad. While this should never have gone on so long, today, 17 years later, most planetary scientists ignore the IAU definition in favor of the geophysical one. Now, we need to get the media, educational establishment, and other venues to recognize that this issue remains unsettled and that the IAU position should not be treated as objective truth but as one side of an ongoing debate.

Just today, Celestron sent an email describing today as “Pluto Demoted Day,” with a link to an article that states only the IAU position without even acknowledging the geophysical definition.

For many of us, today is not “Pluto Demoted Day.” It’s “Pluto Resistance Day.” And we need to get the word out there that there is another view, that there is science behind classifying Pluto as a planet, and that no individual or group should be given the right to impose its view on all humanity.

We will never give up, and we will never stop fighting this wrong. Galileo was eventually vindicated, and so will adherents of the geophysical planet definition.

The resistance continues.

Please sign this petition to save New Horizons as a planetary/Kuiper Belt mission

On April 12 of this year, I wrote about a NASA proposal to prematurely defund New Horizons as a planetary mission and to transfer control of the spacecraft to the agency’s heliophysics division, a move that would replace the current mission team, which have given decades of service to it.

Now, you can help advocate for New Horizons remaining a planetary mission through the years it traverses the Kuiper Belt by signing this Change.org petition organized by the National Space Society.

For no clear budgetary or scientific reason, NASA’s Science Mission Directorate is considering ending it as a planetary mission and transferring control of it from the agency’s planetary science division to its heliophysics division.

Eventually, when it leaves the Kuiper Belt, New Horizons will concentrate solely on the heliophysics of the outer solar system. But for now, it still has sufficient fuel to continue studying the Kuiper Belt for another five years. It is the only vehicle in place to conduct in situ study of this region. Arbitrarily ending the planetary mission half a decade early wastes a unique opportunity that neither NASA nor any other space agency is likely to have for decades.

The petition closes on Monday, September 4, which is Labor Day, and the National Space Society hopes to get up to 10,000 signatures by then to stand up for New Horizons remaining a planetary mission until it leaves the Kuiper Belt. So we need to act quickly.

If you are American, these are our tax dollars at work, and we deserve a say in how they are used. This is the only chance in decades to explore the Kuiper Belt and possibly find a third close flyby target. We should not waste it!

And if you’re of a different nationality and a supporter of planetary exploration, you can still sign this petition and are urged to do so. New Horizons made headlines around the world when it flew by Pluto and then by Kuiper Belt Arrokoth. Its exploration of the Kuiper Belt is not just an American project; it is a human one.

Please take this action to save New Horizons as a planetary mission and share this petition with as many people as possible by September 4. Thank you in advance.

John Vester Followup Article on "Pluto: Planet or Not"

The following is a followup by John Vester addressing responses to his original article published in Analog, titled "Pluto: Planet or Not."

Since the time the essay was published in Analog magazine, other than a few friends telling me they thought it made sense, I have received some pointed critiques of the science.

I also received some links to relevant scientific papers:

1) A Geophysical Planet Definition

https://www.hou.usra.edu/meetings/lpsc2017/pdf/1448.pdf

2) Reductionist vs. Folk Taxonomies in Planetary Science

www.hou.usra.edu/meetings/lpsc2021/pdf/1083.pdf

3) An Organically Grown Planet Definition

https://astronomy.com/magazine/2018/05/an-organically-grown-planet-definition

4) Ignore the IAU! Dwarf Planets are Planets Too

https://www.youtube.com/watch?v=m-WsYl_wWNo

Five main objections to my Linguistic Planetary Definition have come to my attention.

1. The proposed linguistic definition lacks simplicity because some objects that would be considered planets by this scheme can become captured into orbit around another object, making it now a moon by my scheme.

ANSWER – This objection is a defense of the misguided attempt, on both sides, to infuse the definition of the word “planet” with too much baggage in support of the astronomer’s or the planetary scientist’s preferences.

The essence of the linguistic definition is simplicity. A planet is simply anything that orbits a star. If some object changes from one category to another, it should not be a problem. When a tadpole changes to a frog, or a caterpillar into a butterfly, there is no confusion. So if a rock changes from being an asteroid to being a moon, it should not be upsetting. It happens at the subcategory level without complaint. An asteroid sometimes comes back to life, as it were, and is treated as and called a comet.

2. My “Power to the people!” line drew some ire. It’s up to science, I am told, to raise the public’s understanding of nature. The public did not accept the notion of Earth as a planet, but Copernicus and science prevailed, even though the public was wrong. We shouldn’t be dumbing down scientific terminology to satisfy the views of the public.

ANSWER – Setting aside the fact that the Copernican revolution was a revolution in understanding, not a revolution in nomenclature, the linguistic approach does reclaim some words for the language, allowing science full rein over all the subcategories.

The overarching categories, like planet, moon, and star, ought to be based on simple, discriminating principles, such as what it orbits, or whether it has achieved nuclear fusion in its core. To burden the word “Planet” with questions of shape, geologic activity, clearing of orbits, etc. serves no purpose in helping educate the public. These confusing stipulations may please the scientists on those teams, but will only result in the division and the gnashing of teeth, as we see now regarding Pluto.

3. I have been accused of including hearsay by relating the story of “snow” and the languages of the Eskimos/Inuits.

ANSWER – While I included the words “It is said” in an attempt to make it clear that I make no claim as to the truth of the story, it does illustrate an important point. As one becomes more intimately involved with something, clarity of communication demands more precise language about it.

As we enter a golden age of astronomy, thanks to incredible probes, like New Horizons, and fantastic telescopes, like JWST, and which we will continue to launch, and as findings, news, and discussions of mission discoveries continue to proliferate, we need to clarify out terminology.

The scientific community is in a similar position to what Zoology was like in the 1700s. What we need is a modern day Carl Linaeus to develop a taxonomy for space objects. But the overarching category names should not be discarded. In spite of Linaeus, we still talk about horses and dogs. And we still observe that there are plant, animal and mineral kingdoms. How is star, planet and moon different?

4. Fault has been found with my statement that originally all planets were mere specs of light in the night sky. On the contrary, the sun and moon are held up as proof.

ANSWER – This proves nothing. Back then, as now, the sun and moon are not, neither of them, planets. The GPD folks are eager to start calling large moons planets, which seems to me a step in the wrong direction.

5. I have been taken to task for ignoring or missing “one of the greatest insights in scientific history,” which is that space objects large enough to be complex and, as Galileo put it, to be homes for life and civilizations, are planets. During the 1700s and 1800s, science dropped the “homes for life and civilizations” part, but they kept the size and complexity part. This important central insight is a central part of the GPD argument.

ANSWER – Let’s notice that science gets it wrong too. Galileo’s speculations about life and civilizations were dropped so as to keep lifeless planets in the planet club. Note too that the GPD would have us referring to our moon, and others, as planets because they show evidence of geologic activity. How confusing compared to simply referring to what something orbits, or compared to what we have seen and heard in hundreds of years of literature and song.

Let things like size and shape and complexity be handled in research and at the subcategory level. If the GPD wants Luna (or Titan, or Enceladus, etc.)to be planets, what happens if the supposed geologic activity completely ceases? And what if it starts up again? The chance exists that this will happen at some point and require new GPD designations. But that’s the crux of Objection #1!

With all that said, it occurred to me that there is a sort of grey area that should be appreciated.

My proposal is from a spoken language stand point. Objections to these ideas comes from a science stand point. While science may feel an obligation to reach down and educate the public on what science has learned about how the world works, I resist the notion that science always knows best.

We, the people, should lay claim to some basic words, like star, planet and moon. If we do not, science can make a mess of things, as they did with the word “metal.” In common parlance we know what metals are. Hard, shiny, bendy. Good enough for everyday use. Chemistry has expanded on the definition to mean any element or alloy that handles electrons in certain ways. Useful and interesting. But the Astrophysicists use the word to man any element in the periodic table heavier that hydrogen or helium. How is this helpful in educating the public?

In conclusion, the overarching categories, “star,” “planet,” and “moon,” should be the province of the man on the street, with simple, easy to understand criteria. All the many subcategories should be the province of science.

Adrift in the Kuiper Belt? - Alan Stern of the New Horizons Mission

"Planet or Not" Guest Blog by John Vester

 

Today, July 14, 2023, is the eighth anniversary of New Horizons' successful Pluto flyby in 2015. In celebration of this occasion, I am sharing a guest blog by John Vester, which was initially published in the March/April 2021 issue of Analog magazine.                                                                                                       

Planet or Not?
by John J. Vester

          In 2015, after 16 years of planning and herculean effort, Alan Stern and his team took us all to Pluto aboard the New Horizons planetary probe. But something else that happened in 2006 (the year of the New Horizons launch) cast a slight shadow over the mission, and has since tasked Stern almost as much as the mission itself did…the loss of Pluto’s status as a planet, and the struggle to regain it.

When The International Astronomical Union (IAU) voted to demote Pluto to “dwarf” status, they embarked, Stern argues, on a course for which their membership was unqualified to make pronouncements. The arguments pro and con are many, rage still, and have crystallized into two opposing camps, all of which is brought into clear focus by the April 28, 2019 debate, hosted by the Philosophical Society of Washington DC.¹

The IAU Planetary Definition (IPD) has three main parts. 1) A planet orbits the sun, 2) it is large enough to achieve a spherical shape, and 3) a planet clears its orbit of other objects. Against criticism, the adherents of the IPD mainly defend the vote on procedural grounds (although they admit it probably should not have been planned behind closed doors). Naming and science, they say, are two different things and naming is important. It helps science function by creating a common language. (It should be pointed out, though, that the IAU did not name anything, but merely attempted to change the definition of an existing word.)

Stern maintains that expertise is also important, and promotes his Geophysical Planetary Definition (GPD). He points out that planetary scientists, who were significantly absent from the vote in Prague, and who are more qualified than astronomers to decide on planetary nomenclature, do not use or recognize the IPD. The GPD considers a planet 1) to be a sub-stellar object that never underwent fusion, and 2) has enough mass to assume a spherical shape.

The IPD is more concerned with the dynamics of an object…where it is and what its orbit is and does. The GPD is more about the object itself…what it is regardless of where it is. The IPD confines itself to objects in our solar system, while the GPD applies to exoplanets equally. The IPD’s clearing of orbits requirement has the odd consequence that the same object can be considered a planet at one distance from the sun, but not if farther away. GPD proponents are quick to point out that under the IPD’s clearing of orbits stipulation, even the Earth would not qualify as a planet.

Both definitions set up complex requirements for entry into the planet club. One of the reasons given in support of the IPD is the seemingly absurd notion that we need to limit the number of planets so school children won’t have so many to memorize. Yet there are still 50 states and the periodic table still lists north of a hundred elements.

Both definitions are a little vague about moons, rogue planets and brown dwarfs. Each side snipes at the other, basing some of their arguments on outlier cases such as these. This is no way to establish overarching categories.

There has to be a simple way out of this morass, and maybe there is. Here’s an immodest proposal that does not offer either side a conclusive victory, but does not condemn either to final defeat. All combatants agree that this Pluto/planet dustup is a categorization problem. But more than that, I think it is a language problem.

So my proposal, a linguistic solution, is this: Anything orbiting any star is a planet, and anything orbiting a planet is a moon. That simple.

Stern defends the GPD by pointing out that neutron stars, pulsars, and red giants are all still considered stars. (This points up a conundrum in the IPD—calling something it does not consider to be a planet a “dwarf planet.”) To illustrate his point, Stern shows a picture of a Chihuahua and a Great Dane next to each other. Although quite different in size and appearance, we still call them both dogs. There would be no value (not to mention the tidal wave of push back) if scientists demanded we all start calling these animals, instead, canis lupus familiaris.

Imagine the uproar if the IAU began to tinker with the definition of sun, or star. For many things, the common name in the language is best.

So it is with the word “planet,” which originally was a language thing. It meant “wanderer.” It had nothing to do with size. Back then, the planets were mere pin pricks of light that moved (wandered) relative to the background stars (and also exhibited weird apparent retrograde motions at times). But we know that planets don’t wander. They have circumscribed perambulations…they pace. So “planet” has been decoupled somewhat from its original, literal meaning.

To understand the proposed linguistic rationale being offered here, consider the word “snow”. Since we do not live constantly with snow, the English language (along with many/most others) has only one word to encompass the entirety of this seemingly homogenous phenomenon (though extremely varied in the details of its many manifestations). But expertise does matter. Therefore Eskimos/Inuits, who live their whole lives in an intimate relationship with snow, have, it is said, a great many words, one for each of its important forms, all subsumed under the general category that we label “snow.”

With our quickly expanding knowledge of the bodies in our solar system, planets are no longer mere specks of light wandering the sky, but real worlds. This has resulted, during the last forty years, in a huge increase in the number of scientists who consider themselves planetary scientists, not astronomers, and very few of them are members of the IAU, and this is telling.

But the expertise of scientists, whether astronomers or planetary scientists, is not entirely relevant here. They commandeered the word planet from the language of the common people. It is the language (therefore people, not scientists) that has jurisdiction. The Chihuahua/Great Dane example is absolutely relevant. Great Dane is a subcategory of dog. As for heavenly bodies, we know enough about them now, thanks to all those planetary scientists, that we should be more concerned with subcategories. We already speak of the “rocky planets,” the “gas giants,” and the “ice giants.” We understand all these to belong under the heading of “planet.” Why not bring asteroids, comets, Trojans, KBOs, TNOs, and Oort Cloud objects into the same grouping? They should all take their places as subcategories of planets.

This is certainly simpler than the tortuous redefining attempted by the IAU. Clearing an orbit is irrelevant by this linguistic definition. Objects in uncleared orbits would themselves be different flavors of planets.

“Spherical” is a matter of degree, not kind. Even if it mattered, Ceres and Pallas, once considered planets, are today in limbo as spherical asteroids. They are all planets again by the proposed new scheme, and maybe we’ll call them “rocky dwarfs.” As for Pluto, Eris, Sedna, etc., how about “icy dwarfs?”

Size is also irrelevant by this proposed revision to the definition of the larger category, planet. But this shouldn’t create difficulties in discussing these objects. Asteroids would be planets we call “asteroids” (its subcategory). A rock or even a grain of sand orbiting the sun is a planet that we would call a grain of sand or a “meteor.” Once it burns up in a planetary atmosphere or hits the ground and stops orbiting the sun, it is no longer a planet and we might call it part of a “meteor shower” or a “meteorite.”

Even the outlier cases can be easily dealt with by this suggested protocol. The GPD allows that some moons can be considered “worlds” or “planets.” The only way a moon could be proclaimed a planet would be if the center of mass, around which both objects revolve, falls, not inside the larger body, but in the space that separates them. Then it is a double planet, or a binary.

Rogue planets, called in the GPD “unbound planets” become “unbound bodies.”

A brown dwarf is simply a planet if it never initiated fusion in its core. If it doesn’t orbit a star, it is an unbound body.

There will, of course, be scientific hairsplitting on whether an object belongs in one subcategory or another. For the rest of us, though, it will be much simpler to know that they are all planets, simply by virtue of the fact that they orbit a star. One of the criteria Stern offers for recognizing a good naming solution is that it is simple, logical, and intuitive. What could be easier for the general public to understand and embrace than this language-based solution?

The IAU is probably the best place to do the subcategory hairsplitting (provided the planetary scientists are represented and have their say). For my money, the IAU should pass a resolution adopting this idea, and also abdicating their jurisdiction over the overarching category, planet.

Words matter. So, by this proposal, planet would become the people’s word again. Power to the people!


Endnote:

¹ https://www.theverge.com/2019/4/28/18518014/pluto-debate-planet-definition-alan-stern-international-astronomical-union

New Horizons Should Remain a Planetary Mission

 

A little-known proposal is threatening the future of NASA’s New Horizons mission, and for reasons unknown, the space press has not reported on this development whatsoever.

This needs to change, as the public has the right to know that one of this country’s most successful planetary missions is in danger of being shut down before its time.

Launched in 2006, New Horizons has captured breathtaking images of Pluto and its large moon Charon, as well as a Kuiper Belt Object (KBO) one billion miles beyond it.

From the beginning, New Horizons has been a planetary mission. Its exploration of not just Pluto but primitive KBOs that have remained unchanged since the solar system’s earliest days continues to reveal new insights into the solar system’s formation and evolution.

Now, New Horizons as a planetary mission is facing premature cancellation. For no clear budgetary or scientific reason, NASA’s Science Mission Directorate is considering ending it as a planetary mission and transferring control of it from the agency’s planetary science division to its heliophysics division.

Incredibly, this would remove the current New Horizons team, many of whom have dedicated decades to seeing it through from an idea to launch to Pluto and beyond. Instead, it would put the spacecraft under the control of a new heliophysics team.

When a similar move was done with the Voyagers once they ran out of planets to visit, the mission’s leadership and most of its team was allowed to remain in control. It makes little sense to remove New Horizons from the loyal, dedicated group who fought for it every step of the way and are now guiding it through the uncharted territory of the Kuiper Belt.

Such a move is nothing less than a slap in the face to a team that has poured their minds and hearts into one of NASA’s most successful planetary missions and still have so much more to give.

Eventually, when it leaves the Kuiper Belt, New Horizons will concentrate solely on the heliophysics of the outer solar system. But for now, it still has sufficient fuel to continue studying the Kuiper Belt for another five years. It is the only vehicle in place to conduct in situ study of this region. Arbitrarily ending the planetary mission half a decade early wastes a unique opportunity that neither NASA nor any other space agency is likely to have for decades.

Small KBOs like Arrokoth, which New Horizons flew by in 2019, contain the building blocks of the solar system. The New Horizons team has spent the last few years using very large ground-based telescopes to search for a third flyby target, for which the spacecraft has roughly as much fuel as for the Arrokoth flyby.

What sense does it make to throw away the chance to observe yet another KBO up close as well as many others from a distance?

Currently, no other missions to the Kuiper Belt, and none are even being planned. New Horizons is literally our only chance to explore this region of the solar system in situ for decades.

This proposal is not about money. The move would not save any money, replacing one team with another. Neither does it make scientific sense. It is a senseless step that wastes precious resources for no benefit.

New Horizons has had multiple scientific successes because of the hard work, dedication, and passion of its team. We should be rewarding these scientists and engineers, not throwing them away and forfeiting the chance to study this remote, fascinating region of the solar system for another five years.

Why hasn’t the space press reported on this senseless proposal? The public, who fund NASA, deserve to know that the agency is on the verge of making a wasteful, unnecessary move.

New Horizons thrilled children and adults around the world when it revealed the beauty and complexity of Pluto. Today, the public deserves to know that this mission faces premature termination for literally no reason. Space journalists around the world need to tell this story while there is still a chance of preventing this destructive move.

Hear Ye, Hear Ye! Carolyn Porco and Scott Tremaine are Wrong about Pluto!

In a Facebook announcement dated February 14, 2023, planetary scientist Carolyn Porco takes on the role of planetary town crier, stating, “Hear Ye, Hear Ye! Scott Tremaine, renowned celestial dynamicist & a founder (along w/ my thesis advisor Peter Goldreich) of the field of planetary rings, has written a textbook on The Dynamics of Planetary Systems. At my request of some time ago, he included in his book a discussion of the definition of a planet...And what did he find? Pluto is NOT a planet !! Reason has prevailed. Rejoice!

Porco is admittedly an accomplished scientist best known for her work on NASA’s Cassini mission to Saturn. But in this case, she is wrong.

Reason does NOT prevail when a person with an agenda specifically requests that a fellow scientist push that agenda in his book while refusing to acknowledge the ongoing debate and both sides in that debate.

Porco’s position on the planet definition issue is actually more extreme than that of the IAU. She opposes the use of the term dwarf planet because she claims Pluto and Ceres are both asteroids! She states in the comments, “Actually, I don't ever use, and won't, the name 'dwarf planet'. It's inconsistent. How can something be a dwarf member of a category it doesn't belong to?”

Regardless of their own position on this issue, most scientists acknowledge the ongoing debate between dynamicists and geophysicists over the question of defining a planet. Most show respect for the opposing position even if they don’t agree with it.

In my writings and public presentations, I always make the effort to present both views. While I am clear on the view I hold, I believe it would be a disservice to readers and/or audience members to pretend my view is the only one and that all others have been discredited when this is not the case. I would rather members of the public hear both sides of this issue and then make up their own minds than feed them my viewpoint alone.

Porco goes on in subsequent comments to denigrate the geophysical planet definition by claiming roundness means nothing, adding, that the term dwarf planet “actually has no information in it besides 'sort of roundish'. On the other hand, ‘Pluto is a large Kuiper Belt Object’ tells you composition, location, relative size, approximate level of solar illumination, etc. Far more useful.”

To her, there is apparently no difference between tiny, shapeless asteroids and KBOs and objects large enough and massive enough to be rounded by their own gravity, in spite of the fact that the latter have complex processes not seen on asteroids and in some cases, seen elsewhere in the solar system only on Earth and Mars.

Just calling Pluto a large Kuiper Belt Object tells us nothing about its structure, its geology, its atmosphere, the interaction between its atmosphere and surface, its many varied terrains, its cryovolcanoes, its likely subsurface ocean, and its interactions with companion Charon as the solar system’s only binary planet system.

Pluto actually has far more in common with some of the larger, spherical moons in the solar system, considered by many planetary scientists to be secondary or satellite planets, than it does with tiny, shapeless Kuiper Belt Objects like Arrokoth. Today, planets such as Ceres; Jupiter’s moons Europa, Callisto, and Ganymede; Saturn’s moons Enceladus and Titan; Neptune’s moon Triton, and Pluto are the solar system’s top contenders for hosting microbial life due to the growing evidence that they harbor subsurface oceans.

Porco insists that gravitational dominance alone determines what is a planet without ever addressing the fact that this dominance depends on location and can lead to the same object being considered a planet in one location and not a planet in another one. If Earth were in Pluto’s location, it would not gravitationally dominate or clear that orbit.

Furthermore, she states, “But Mercury, Venus, Earth and Mars dominate their orbital corridors. If they hadn't, you wouldn't see them, you'd see a cloud of debris.

Does Mercury actually dominate its orbit, or does the Sun clear out debris there? The answer is unclear. Furthermore, there is no cloud of debris around Pluto. If there were, New Horizons would have had no trouble finding a second and even a third flyby target. The reality is the Kuiper Belt is vast, and most KBOs are nowhere near Pluto but much further out and very scattered.

She goes on to say, “'Round' is a perfectly useless criterion. It doesn't work for those distant bodies for which we don't, and won't for a very long time to come, if at all, have shape information for. So it fails as a metric for categorization...I mention ‘spherical’ but merely because it’s a side effect of (or proxy for) planetary properties and processes I am interested in with categorization in mind. E.g: a degree of planetary differentiation.”

But another commenter points out that gravitational dominance is much more difficult to detect at great distances than is roundness, and that time and the technological advancements that go with it will eventually answer these questions for distant objects, both in our solar system and others.

Additionally, planetary differentiation is very much related to roundness, as she admits in the sentence I bolded above. Active geology begins happening when objects reach the threshold of being rounded by their own gravity. Categorizing Ceres and Pluto as asteroids is bad science because it blurs the distinction between complex objects shaped by their own gravity and tiny ones that are often little more than rubble piles, held together only by their chemical bonds.

One commenter even repeats the false claim that Mike Brown discovered dwarf planets larger than Pluto despite the fact that no such dwarf planets have been found. Eris was initially thought to be larger than Pluto, but in November 2010, a team of astronomers led by Bruno Sicardy observed it occult a star and found it to be marginally smaller than Pluto though slightly more massive.

The persistence of this misconception after more than a decade is an example of why the IAU definition has harmed science by widely spreading confusion and incorrect information.

Unfortunately, the tone of the discussion in the comments takes a turn for the worse when Porco resorts to personal attacks against New Horizons Principal Investigator Alan Stern and other supporters of the geophysical planet definition, demeaning them by calling them “Pluto fanatics.”

Here are some examples of her inappropriate personal attacks:

“The Pluto fanatics were desperate to get a Pluto mission, and it was deemed of vital importance to maintain Pluto as a planet, so they would have more justification. They were practicing politics, not science.”

This is blatantly false. New Horizons was already approved and had already launched when the IAU vote took place. Most New Horizons scientists view Pluto as a planet because they favor the geophysical definition over the dynamical one. It is a purely scientific disagreement.

As New Horizons planetary scientist Cathy Olkin noted, "I naturally refer to Pluto as a planet because that seems like the right moniker. It has an atmosphere; it has interesting geology; it orbits the sun; it has moons. 'Planet' just seems right to me."

Porco went on to comment, “Stern has admitted he wanted Pluto to be a planet because he was afraid New Horizons wouldn’t be chosen if it wasn’t. He DOES appeal to emotions. You want to compare our respective domains of expertise? Stern did a mission to Pluto. I ran an experiment and published papers that required knowledge on my part in atmospheric meteorology, the kinematics and dynamics of planetary rings including faint rings of tiny micron-sized particles, the geology, geophysics and geodesy of planetary satellites, the tidal interactions between planetary bodies, the geysering eruptions of Enceladus, and a lot more. So, a body like Pluto is NOT outside my field.”

Again, her first statement is false. And while Porco did accomplish everything she states, Stern has also published numerous papers on many of these same subjects and is the world’s leading Pluto scholar. And his advocacy and leadership of the New Horizons mission essentially unveiled Pluto to the entire world.

Porco should feel secure enough in her own accomplishments to not belittle another scientist who clearly made extensive contributions to planetary science just because he disagrees with her on planet definition.

In one remark, she responded to a commenter by saying, “You are clearly an ignoramus and should keep your mouth closed.”

She even goes as far as comparing opponents of the IAU definition to climate deniers!

Ad hominem, or personal attacks, are a sign that someone is losing the debate.

Significantly, Porco blocks me on Twitter, and I could not comment on her Facebook page because it only allows those she permits to comment.

But I will not keep my mouth closed. I will not be silenced, and neither will advocates of the geophysical planet definition.

If someone has to resort to censorship to force their view on the world and disallow any comments that disagree with their view, they are NOT causing reason to prevail. They are enforcing tyranny. And that is anything but a reason to “rejoice.”

New Horizons: NASA’s Mission to Pluto and the Kuiper Belt, by Alice Bowman: I Heart Pluto Festival 2023

The Future of New Horizons: An Interview with Dr. Alan Stern | I Heart Pluto Festival 2023

Planet Pluto Discovered 93 Years Ago Today, February 18, 1930

 

On February 18, 1930, exactly 93 years ago today, 24-year-old Clyde Tombaugh discovered Planet Pluto while blinking between two photographic plates of the same part of the sky taken six days apart at the Lowell Observatory in Flagstaff, Arizona.

He found a tiny dot that moved against the background stars from one plate to the next and thus succeeded just over a year after arriving at Lowell Observatory to take up the search for a new outer solar system planet, begun many years earlier by observatory founder Percival Lowell.

Now close to 130 years old, the Lowell Observatory is today holding its annual “I Heart Pluto” celebration to commemorate the discovery. The 13-inch Lawrence Lowell telescope Tombaugh used to take the photographic plates, recently restored, still sits within its original dome and is viewed by visitors every day.

Discoveries are not always well understood at the time they are made. In Pluto’s case, the new planet was too small to be resolved into a disk, leading some scientists to speculate that it might be a moon of a not-yet discovered larger parent planet.

Eventually, telescopes became powerful enough to resolve Pluto into a disk, but even Hubble images taken during the 1990s were fuzzy. The real revelation of Pluto in all its glory happened in 2015, when the New Horizons spacecraft flew by that world, imaged its varied terrains, and returned data that is still being studied and analyzed today.

Tombaugh and his fellow astronomers in 1930 had no way of knowing that they had found the first of many small planets in what is now known as the solar system’s third zone. They certainly had no inkling that the newly discovered world was one of many solar system objects that has a subsurface ocean possibly capable of hosting microbial life.

With the recent renewed interest in UFOs, it is important to remember that as of today, we have not even determined whether any other place in our own solar system harbors life. What we have discovered is that small planets Pluto and Ceres, as well as various moons of the gas and ice giants, likely have oceans beneath their surfaces that could potentially host microbes. Among that growing list of worlds are Jupiter’s moons Europa, Ganymede, and Callisto; Saturn’s moons Enceladus, Titan, and possibly even Mimas; Neptune’s moon Triton, and possibly Pluto’s binary companion Charon.

Distant planets like Eris and Sedna could also potentially host such oceans, but we won’t know until we send probes to study them up close.

On February 18, 1930, Clyde Tombaugh had no way of knowing that he had not only unlocked a third zone of the solar system, but also discovered a new class of ocean worlds that could be the prime locations for life taking hold beyond the Earth.

While it is clear that any extraterrestrial life in our solar system is limited to microbes, finding evidence of such life on any world would be one of the most significant scientific discoveries in history, as it would confirm life got started on worlds other than Earth.

Tombaugh also could not have known that the world he discovered was not a dead rock, but a geologically active planet that appears to have an internal heat source. No one expected something like this so far from the Sun. Today, the discovery of Pluto’s complexity and activity raises the possibility that other, even more distant worlds, could also be active planets.

Our technology is not yet at the level of being able to discover Pluto-sized planets in other solar systems, but the ability to do so is likely just a matter of time. While his search was for a gas giant planet, Tombaugh discovered the first in a new subclass of planets, the dwarf or small planets, largely but not solely present in the outer solar system. It is reasonable to hypothesize that other solar systems could also have regions like this, with scattered small planets that might be hiding subsurface oceans.

Some in the astronomy community did not give Tombaugh sufficient credit for his discovery back in 1930. His name was not even mentioned in Lowell Observatory’s press release announcing the discovery. Some astronomers of the day even looked down on him because he was a 24-year-old with just a high school education, not an astronomy PhD.

Yet even here, Tombaugh set a new trend though it would not become a “thing” until many decades later. This trend is that of astronomical and planetary discoveries being made by ordinary citizens, amateur astronomers, and even kids, who don’t have PhDs, but are passionate about the universe. Internet and telescope technology have opened the discovery process to interested citizens around the world, who have discovered exoplanets, brown dwarfs, supernovae, etc.

In so many ways, Tombaugh was far ahead of his time. This is also true of his staunch support of Pluto’s planethood. Doubts about that began not in 2005 but in 1930, soon after its discovery. Yet Tombaugh never wavered in his position even though he did not live to see the New Horizons flyby. Today, we know that Pluto is actually part of a binary system with Charon, meaning it is not one but two planets! The system’s four smaller moons orbit not Pluto itself but the center of gravity between Pluto and Charon.

This is a day to celebrate Planet Pluto and its opening of new frontiers in solar system and planetary studies. I personally wish I could be at Lowell Observatory’s I Heart Pluto celebration and hope to to be there for the centennial in 2030.

This year’s celebration will conclude with two talks that will be livestreamed online. The first, “The Future of New Horizons,” will be presented by Alan Stern on Sunday, February 19, at 7 PM Mountain Standard Time, which is 9 PM Eastern time. The second, “New Horizons: NASA’s Mission to Pluto and the Kuiper Belt,” by New Horizons engineer and mission operations manager Alice Bowman, will be presented on Monday, February 20, at 7 PM Mountain time/9 pm Eastern time.

Happy Discovery Day, Planet Pluto!

I Heart Pluto Festival Returns to Lowell Observatory

It is almost the 93rd anniversary of Pluto's discovery on February 18, 1930, and that can mean only one thing--Lowell Observatory's annual I Heart Pluto celebration is back! Find out more here! While celebrations on February 18 will be in person at Lowell Observatory, there will be two talks livestreamed online on YouTube, one on February 19 and the other on February 20, as follows:

Sunday, Feb. 19, 7 pm: The Future of New Horizons: An Interview with Dr. Alan Stern

Monday, Feb. 20, 7 pm: The Latest News from Pluto and Arrokoth, with Alice Bowman, Engineer/New Horizons Mission Operations Manager, Johns Hopkins University Applied Physics Laboratory