Pluto and Her Broken Heart
Why is Pluto not a planet?
This is a topic where Pluto’s broken heart crosses ours..
On this article we focus on IAU‘s rearrangement about classification and definition of planetary bodies in Solar System which consequently downgraded Pluto’s planetary status. For the opposing ideas and alternative planetary definition proposals, see our next article: Is Pluto A Planet?
Let this article begin with some questions:
Is Pluto still a planet? If not, what is Pluto and why is Pluto not a planet? What happened to Pluto? Where is Pluto now? Is Pluto feeling well?
Here we are to answer some heartbreaking questions.
You would feel hurt if you were downgraded right? Probably, so does Pluto!
Is there any way to fix Pluto’s broken heart? Let’s see.
Is Pluto A Planet? – Brief Explanation of What’s Known
Is Pluto a planet? A question of interest for more than a decade.
From the date of discovery (1930) till 2003, this beauty was an ordinary and content planet. After 73 years, this whole story began with Eris, the scapegoat.
On 21 October 2003, discovery of planet Eris took place. Similar to planet Pluto, Eris is also located in Kuiper Belt; and its orbit interferes with Pluto’s orbital path time to time.
Since the size and the orbit of Eris is similar to Pluto’s, astronomers started to think how to redefine such objects as there were a lot more candidates to be discovered from Kuiper Belt. In addition to that, characteristics of those were very similar to Pluto’s.
That limited the number of options with two: Either new discoveries should have been called ordinary planets or Pluto should have been re-classified among with others.
It took more than 2.5 years for IAU to consider this. And time helped to those and their hidden agenda. Discovery of 2 more planetary bodies, Haumea and Makemake took place in between helped to justify all. But not in our hearts!
IAU 26th General Assembly: Messenger of Dark Days
It was 24 August 2006 when IAU (International Astronomical Union) gathered for its 26th General Assembly. On this routine meeting, two main subjects of discussions out of six were as follows:
- Definition of planets
- Definition of Pluto-class objects.
IAU members had been voting and taking the decisions about those subjects, where only 5% of worldwide astronomers were participating.
On the announcement page of IAU, it’s stated that “the votes for Definition of Planet ‘was not counted’ but the statement passed with a great majority”. And next statement about the voting says: “Definition of Classical Planet” had 91 votes in favour, but many more were against. So actually there were no counts. Suspicious!
Updated Definition of A Planet
New definition for an ordinary planet as announced by IAU on 24 August 2006 is as follows:
“A planet is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.”
Why Is Pluto Not A Planet Any More? – Being Kicked Out of Planetness
According to IAU, newly introduced definition of dwarf planets involved (a) and (b) above, but the opposite of (c). So this meant planet Pluto was not a planet any more, and was re-classified in a new concept: A dwarf planet.
Why is Pluto a dwarf planet? In other words, why does IAU call Pluto a dwarf? What is a dwarf planet? Let’s see in details.
The definition means a dwarf planet should directly be orbiting Sun, should have sufficient mass for a hydrostatic equilibrium and nearly round shape; but didn’t have cleared the neighbourhood around its orbit.
But wait, what does “clearing neighbourhood around the orbit” mean? Because it’s the only matter causing trouble to our beloved!
Clearing the Neighbourhood Around the Orbit
What scientists mean by clearing the neighbourhood is the gravitational power to remove other objects from the effective orbital path. And this includes being free from any kind of orbital resonance (like 2:3 resonance of Neptune and Pluto case).
At this point, there has to be a clear definition about the limits of this orbital suppression because most of the planetary bodies (depending on the distance between each other) are able to influence each other.
Take Earth and Moon for example.
First of all, Moon is always around Earth’s orbital neighbourhood similar to other satellites and planets.
In addition, it’s not only Earth dictating its gravitational power to the Moon, Moon effects Earth’s orbital path and motion as well. And that surely applies to Neptune-Pluto interaction!
Although IAU did not directly refer any of them on its statements, there are some definitions and calculated discriminants offered by different scientists which are related to this subject.
Formulation of Neighbourhood Clearance
In that aspect, there are three seperate constants calculated via dedicated formulas: Stern-Levison‘s Λ (lambda), Steven Soter‘s µ(mu) and Jean-Luc Margot‘s Π (pi) calculated in different manners. Among all these formulas, there are calculated limits for the orbital clearing. And whichever formula is taken into account, all 8 planets successfully exceed the limits where Pluto, Ceres and other Kuiper Belt objects fail by far. (For details of those calculations, follow this link)
Although above formulas scientifically make sense and can draw a line, IAU’s famous article (c) still does not do that. If a planetary object could not clear the other object from its orbit, than the other object (let’s say with a bigger mass) faces the same problem as well. In that manner, when we go one step further and check all 8 “planet“s orbits, none of them will remain as planets, including Earth! For example if Pluto is not a planet, that makes Neptune “not a planet” too.
Why Is Pluto Not A Planet – Main Motive Behind The Decision
Despite above contradiction, we find it logical in its extent when and if discriminants taken into account and clearly stated.
Since statement (c) and hence the planetary definition of IAU is not 100% clear, it did not fully satisfy us and many scientists who contributed for other definitions. This leads with other conclusions about what has happened.
One important thing to mention at this point is: Above stated “IAU’s definition of a planet” does not mention anything about a planet’s (or a dwarf planets’) distance from Sun.
However when you ask the question: “Why is Pluto not a planet any more?” to IAU, one of the answers you’ll get will be: “because Pluto is a trans-Neptunian object”. We as Plutopic believe that this is one of the basic motivations and excuses behind Pluto getting definitively kicked out, although it’s not a part of official definition.
It’s very likely that there won’t be any more planetary discoveries from Sun till Neptune orbit from now on*.
However, there are quite a lot of dwarf planet candidates, which are beyond Neptune and some are similar in size with planet Pluto. In case Pluto somehow becomes a planet again, most of others should be planets as well.
To sum up, we believe this 3-sectioned planet definition of IAU is here to mostly avoid further and frequent changes in textbooks. That’s it!
But if that is the case, what is the scientific or educational benefit of that? It’s hard to say.
Pluto Is Not a Planet Anymore! – What Has Changed About Planet Pluto?
So as a conclusion;
Is Pluto still a planet? Pluto is called a dwarf planet by IAU for some time. And the worldwide press and textbooks mostly agreed with this. However, there are scientists who do not stick with this definition. We will get there.
As mentioned above, the unfortunate statement of IAU took place in 2006. From that date till now, the majority of our knowledge about many Pluto facts is supported by New Horizons Mission. And the mission showed the world that Pluto is an active planet with her geological and atmospherical diversity.
One important and indirect consequence of New Horizons Mission was discovery of new Pluto Moons in Pluto System. And the next one is about the rings of Pluto. Because although the scientists believed the opposite before 2015, New Horizons Mission proved that Pluto has no rings.
However, whether Pluto possessed some moons, rings or not; that does not change anything about IAU’s definition. Because the definition is only about the “orbital neighbourhood“, not the planetary distance. That’s worth to be noted here as it causes confusion for many.
Rather than above, nothing changed about our Pluto knowledge since 2006.
Evaluation of IAU’s Definition
After 1990’s, number of Kuiper Belt Objects discovered has been increasing exponentially. And that was going to cause confusions in terms of classification of Solar System rocks. With that pressure, IAU organization considered a new definition and it was truely painful even just to debate and vote.
It literally took years to conclude the definition for the union. This was a real burden and that’s why we appreciate the efforts of IAU members who are precious astronomers.
IAU is a union consisting of astronomers. And those people are some of the most authorized people on their field. The union makes decisions via leading influences of members and side influences from other astronomers in the world. Considering above, it’s not really wise to expect such committees to take public demands into accounts and make their decisions accordingly.
However, there are lots of planetary scientists, astronomers and people who do not agree with IAU about new planet definition. Even there are scientists who offered seperate planet definitions and they have many supporters. See related article related to geophysical planetary definition.
On above mentioned article we also discuss scientific benefits of this and other possible definitions. Because that’s the only important evaluation of any kind of scientific classification in our point of view.
For now we would like to briefly mention that we believe with proper scientific referrals and a worldwide consensus, IAU’s definition would be a sufficient classification and would be consistent in its own scientific context. But how helpful is it to science, researchers, students and public? That’s another question to answer.
Pluto Is Not A Planet – What To Do Now?
Downgrading of Pluto from ninth planet to a dwarf planet is probably one of the unique scientific classifications running into this much public reaction. While that’s the case, most of the public interest about this topic consists of funny campaigns and jokes. But this makes scientists happy as well, since astronomy and far worlds of Solar System gets more attention one way or another.
Besides, you are reading this article.. The campaigns worked for Plutopic too!
As stated above, we believe we have to leave scientific classifications to qualified scientists and nomenclature experts. Besides that, it could sound harsh but we do not believe that this is public’s or individual’s duty or perfection to correct a scientific classification.
However, the question “Why Is Pluto Not a Planet?” did not only become a global phrase, but also a question asked by several scientists.
Pluto Is Not A Planet – Is There Something You Can Do About Planet Pluto?
In that perspective, we believe there is not much public can do to bring Pluto back to her ninth planet rank. Ok, public pressure generally works and is wise to raise when it comes to governmental decisions and public benefit (which might effect astronomy as well). But this time it is a context of pure science where none of the people have any direct interest.
That’s why it’s hard to say what kind of a scientific contribution “fixing a definition” might provide and what kind of a benefit you could obtain out of this, except a naive happiness. Well, happiness is good in any case. We like happiness 🙂 Anyway, at least this is how we approach this matter.
On the other hand, there are people who made quite a lot of serious efforts including building up campaigns for raising the interest in this topic. And this might have triggered planetary scientists as well. Wait, did we say you can not do anything earlier?
Despite above, if you are still willing to join the Pluto Forces, another thing we can recommend you is to persuade majority of IAU members to revise IAU’s definition of planets as IAU seems to be the only organization handling such astronomical classification job.
In case you accept such challenge, feel free to start with quoting below:
“Is it worth to offend a planet for the sake of a better definition? That’s something to think about.“
* Our hypothesis excludes dwarf planets (as if it is a thing!) where there is still a slight possibility.
STAY TUNED FOR OUR NEXT ARTICLE WHICH WILL PROVIDE DETAILS AND REVIEWS ABOUT IAU’s and GEOPHYSICAL DEFINITIONS!
UPDATED ON 11 OCTOBER 2019
References
- Wikipedia
https://en.wikipedia.org/wiki/Dwarf_planet - IAU
IAU-0603 Press Release:
https://www.iau.org/news/pressreleases/detail/iau0603/
Pluto and the Developing Landscape of Our Solar System
https://www.iau.org/public/themes/pluto/
Clearing The Neighbourhood
https://en.wikipedia.org/wiki/Clearing_the_neighbourhood
- We aim to build a proper Pluto encyclopedia and your contributions are highly appreciated!
- Any deficiencies on this article? Please type to below comment box or contact us from this link. We are ready to check and clarify.
There is another backstory which is more embarrassing about who orchestrated this definition change etc.. It was a personal vendetta between 2 individuals (both deceased now) w/one promising the other that Pluto will not be a planet anymore and pushing that plan thru the IAU.. Then at the IAU Prague mtg podium there was a world renowned AstroPhysicist (not a Planetary Scientist) waving a Pluto Dog stuffed toy urging voters to vote for that flawed definition.. I have that pic too.. so that day you had a lot of non Planetary scientists voting/opining for a definition in which they had no in depth knowledge. Then you have a well known planetary scientist monetizing this so called “demotion” w/ a catchy titled book etc. I call it a sad day for science when buffoonery and ignorance takes over a debate what should be science driven. Please do read Alan Boyle’s book end to end too. Thanks for attempting to write up on a topic which needs to be kept alive.. I say there more than 9 planets, the Geo Physical definition is the logical definition. Its a shame that now postulated objects (never imaged) are being termed planets. Thats how low the debate has gotten too. Maybe these postulation do generate research funding in days when $s are hard to come by.. Finally: Here is a Planetary Status debate between the IAU ex boss and a Planetary scientist worth watching.. https://www.youtube.com/watch?v=3AFtgZP6Aa8
Pluto should be a planet , along with Eris, Humea, and Make-Make, and any others found out there. Orbiting the sun should be the criteria.
There are numerous problems with this article, starting with the conclusion. Yes, there is a lot members of the public can do to support Pluto’s planethood. For one, they can reject the notion that only the IAU has the right to determine what is and is not a planet. Science is NOT decided by decree of “authority.” An object does not suddenly become “not a planet” because of a vote by just 424 people.
This debate is not about anyone being “hurt.” It is about who gets to decide scientific matters. There is a continuing debate about Pluto’s planet status, but you failed to acknowledge that another side, one supported by leading scientists, even exists. Alan Stern, principal investigator of NASA’s New Horizons mission, is the person who first coined the term “dwarf planet” back in 1991, and he did so intending to designate a third class of planets in addition to terrestrials and jovians, not to designate a class of non-planets. The IAU essentially misused his term.
You say, “IAU is a union consisting of astronomers, similar to other scientific committees in the world. And those people are the most authorized people on their field. ” In this case, that statement is false. Only four percent of the IAU voted on the controversial 2006 definition, and most were NOT planetary scientists but other types of astronomers. Their decision was immediately opposed by an equal number of professional planetary scientists who stated they would not use the definition. After these planetary scientists repeatedly asked the IAU to reopen the planet debate, they finally decided to go their own way and ignore the IAU definition altogether.
In early 2017, planetary scientist Kirby Runyon introduced an alternate, geophysical planet definition that read, “A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.” Many planetary scientists prefer this definition, as it defines planets first and foremost by their intrinsic properties rather than by their location.
New Horizons revealed Pluto to have the same planetary processes and structures as the solar system’s larger planets. It is geologically active with flowing glaciers; a nitrogen atmosphere; weather produced by interaction between its atmosphere and surface; windswept dunes; geological differentiation into core, mantle, and crust; cryovolcanism, and even a subsurface ocean that could host microbial life. Yet the IAU showed no interest in these findings; having made up their minds, they did not want to be confused with the facts.
The public can do many things to support Pluto’s planethood. Teachers at all levels can teach the controversy rather than present one side as an ongoing debate. People can buy books like Alan Boyle’s “The Case for Pluto,” David Weintraub’s “Is Pluto a Planet,” and Alan Stern’s “Chasing New Horizons.” They can vote with their dollars and buy solar system toys, books, mobiles, and products that include Pluto (there are many). They can approach their Boards of Education and ask them to teach the controversy. They can educate themselves about the debate and the geophysical definition and write articles about it in newspapers, magazines, websites, research papers, etc. They can come together to reject the IAU definition and anything else that tries to do science by decree of “authority.” They can check out my 13-year-old Laurel’s Pluto Blog, make up their minds not to use the IAU definition or planet count, and join the Pluto resistance.
As planetary scientist Phil Metzger emphasized recently, “So start calling Pluto a planet right now. Add to the consensus, because that’s how science makes progress, by one person at a time being convinced of the truth and adopting it. Science is not decided by votes and you are not required to submit to nonsense.”
I agree with the Planetary Scientists.. on this Matter and support the decision.. especially the support of Dr. Alan Stern, Kurby Runyon, and Dr. Phil Metzger on this status of Planet.. ive been supporting a definition of planet.. directed only solely by planetary scientists.. I never supported IAU’s Decision i have rejected it.. ive always called them planets Equal to our very own.. regardless IAU’s decision in my opinion was discriminating.. and prejudice in my eyes by the IAU..
I support the Planetary Scientists on their new definition.. Geophysical Definition of planet.. and what it means on an educated level.. IAU’s view on the matter is and has been flawed..
Bottom Line~ PLANET IS A PLANET PERIOD!!!!!!!!!!!!!
regardless of where or size.. it doesnt matter if a planet orbits a planet or a planet orbits a star or a planet orbiting a galaxy.. point is.. no matter where it is.. in my view its a planet plain and simple
Hello Laurel,
Thanks a lot for your valuable comments and nice to hear from warriors that are on the field for Pluto 🙂
Also special thanks for the additional invaluable information about the background of this discussion and about planetary scientists’ approach on this matter.
Actually we were planning to prepare a seperate article focusing on the opposing planetary scientists, astronomers and public opinions on this subject. That’s why the title and content of this article includes -only- “Why is Pluto Not A Planet” and we did not add any sub-topics about the opposing crowd.
Our website is a fresh one and we are still in progress about building up our basic article database. You might have caught us unguardedly 🙂
However it’ll be great to start that article referring to your comments. Please keep following us!
From the beginning, Plutopic point of view is and will always be dependent on nothing but science and rational scientific methods wherever it applies.
That’s why, first thing we mentioned on our article is IAU’s exact definition. Than stated the “defined” difference between a planet and a dwarf planet by IAU. We had to follow/comment against IAU’s definition because this is the definition we are opposed to.
Plus, IAU definition is the “only statement written by a globally recognized astronomical community”. You mentioned “Their decision was immediately opposed by an equal number of professional planetary scientists who stated they would not use the definition”. We’ve read several different statements of different individual astronomers and planetary scientists about this matter. However, we believe the main problem here is, those planetary scientists were not sufficiently united for a powerful opposition in order to trigger and force IAU.
Anyhow, than we stated that item (c) is the discriminative one, and we clearly stated how we are opposed to this definition with clear examples.
We believe that; if we stick with IAU definition (as we did not mention about geophysical planetary definition), only above matters are directly inclusive in terms of science of astronomy&planets.
For that reason, we’d like to seperately detail our individual thoughts on rest of the topics which can be called as “subjective”:
IAU’s “competence” about naming celestial objects.. Well, of course this is a contraversial issue. Who gives the right for naming celestial objects to a union? Noone can do that, except the union itself!
OK, this might not feel right because we are mostly familiar with different forms of democracy in the world. But just consider: How many decisions of IAU did public oppose before that dwarf planet definition? Well, this time IAU could not work it out smoothly, that’s right.
And another thing: Do public, individual astronomers/scientists or other astronomical unions have to embrace IAU’s definition? Of course not.However, as mentioned on this article, we believe this is a change only for textbooks. And as far as we know, textbooks somehow used IAU definitions..
By the way it’s fantastic to hear that Mr. Alan Stern shares the similar thoughts about “textbook” concerns:
https://www.youtube.com/watch?v=nItBncb8ORM
Maybe IAU could have clearly explained the decision as simple as that. That’d also rid the concerns of us, you and scientists; including the scientific base of concerns you mentioned. But what’s done is done..
So, what makes IAU the union in charge for such naming? Nothing.
Besides all, we believe most fair way (at least for avoiding such contradictions) of yielding such a “single community in charge of such naming/definition etc” could be via astronomical communities formed by worldwide governments/universities. At least that could have reduced such conflicts and reflect the decision of majority.
Despite above, we are not enemies of IAU and their work. This might sound weird and somewhat irrational but, they are doing what noone does. And that looks like the source of their competence, whether we approve their decision about Pluto and other planetary objects or not.
Another thing to consider: If above utopic international community was somehow formed, who could guarantee that the decisions taken by such community make everyone happy?
What is more, we mentioned about “What you can do about Pluto”, yeah. Of course there are more things to do about defining Pluto as a planet again. We’ve talked about “persuading IAU members” on the article, because IAU’s contraversial decision is still the common one used worldwide. And of course, persuading planetary scientists or huge public groups to form a community for such a battle could be another way.
We are here for promoting Pluto and astronomy. That’s right. However this is the part where we mostly joke. Because we believe we need the energy of precious worldwide astronomers and planetary scientists to focus on what they already do: To help humanity understand the universe. Drawing limits and definitive discussions are surely a part of such understanding. But we believe it would not be wise if planetary scientists wasted big amount of energy for such battles instead. All in all, we love learning about Pluto and other celestial objects.
We believe (as stated on our article) such discussions did not actually “downgrade” Pluto, but increased public attention and promoted Pluto instead! This time it’s similar to politics: When you act “despite” public reactions, the topic gets more and more public attention.
But we can still see the good out of it and easily say: Whatever her definition is and who defines it, Pluto has been the winner of this battle since 2006!